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Critical Theory (Frankfurt School)

[ Editor’s Note: The following new entry by Robin Celikates and Jeffrey Flynn replaces the former entry on this topic by the previous author. ]

“Critical theory” refers to a family of theories that aim at a critique and transformation of society by integrating normative perspectives with empirically informed analysis of society’s conflicts, contradictions, and tendencies. In a narrow sense, “Critical Theory” (often denoted with capital letters) refers to the work of several generations of philosophers and social theorists in the Western European Marxist tradition known as the Frankfurt School. Beginning in the 1930s at the Institute for Social Research in Frankfurt, it is best known for interdisciplinary research that combines philosophy and social science with the practical aim of furthering emancipation. There are separate entries on influential figures of the first generation of the Frankfurt School – Max Horkheimer (1895–1973), Theodor W. Adorno (1903–1969), Herbert Marcuse (1898–1979), and Walter Benjamin (1892–1940) – and the leading figure of the second generation, Jürgen Habermas (b. 1929).

In a broader sense, there are many different strands of critical theory that have emerged as forms of reflective engagement with the emancipatory goals of various social and political movements, such as feminist theory, critical race theory, queer theory, and postcolonial/decolonial theory. In another, third sense, “critical theory” or sometimes just “Theory” is used to refer to work by theorists associated with psychoanalysis and post-structuralism, such as Michel Foucault and Jacques Derrida (see these separate entries as well as the entry on postmodernism ).

This entry is primarily focused on the critical theory of the Frankfurt School, but broadens outward at various points to discuss engagements by that tradition with a range of critical theories and social developments. The need for a broad approach to critical theory is prompted today by a range of contemporary social, political, economic, and ecological crises and struggles as well as the critique of Eurocentric forms of knowledge production.

1.1 Origins and Generations

1.2 influences, 1.3 critical theory versus traditional theory, 1.4 studies on authoritarianism and mass culture, 1.5 the dialectic of enlightenment, 1.6 the communicative turn, 1.7 a continuing and contested tradition, 2.1 immanent critique, 2.2 normative foundations for critique, 2.3 reconstructive critique, 2.4 disclosive critique, genealogy, and the critique of normativity, 2.5 current challenges, 3.1 alienation, 3.2 reification, 3.3 ideology, 3.4 emancipation, 4.1.1 gender, 4.1.3 colonialism and post-colonialism, 4.2.1 economic crises, 4.2.2 ecological crises, 4.2.3 political crises, 4.3 critical practices, other internet resources, related entries, 1. the frankfurt school: origins, influences, and development.

The “Frankfurt School” of critical theory is not really a school at all. It is a loosely held together tradition constituted by ongoing debates among adherents about how best to define and develop that tradition. This includes disagreements about methods, about how to interpret earlier figures and texts in the tradition, about whether past shifts in focus were advances or dead ends, and about how to respond to new challenges arising from other schools of thought and current social developments. This section tells a largely chronological story, focusing on the origins, influences, and key texts of the Frankfurt School, and concludes with reference to ongoing debates on how to inherit and continue the tradition.

In their attempt to combine philosophy and social science in a critical theory with emancipatory intent, the wide-ranging work of the first generation of the Frankfurt School was methodologically innovative. They revised and updated Marxism by integrating it with the work of Sigmund Freud, Max Weber, and Friedrich Nietzsche while developing a model of radical critique that is immanently anchored in social reality. They used this model to analyze a wide range of phenomena – from authoritarianism as a political formation and as it manifests in both the nuclear family and deep-seated psychological dispositions, to the effects of capitalism on psychological, social, cultural, and political formations as well as on the production of knowledge itself (for excellent guides, see Thompson 2017 and Gordon et al. 2019).

Max Horkheimer outlined the original research agenda for the Frankfurt School in his 1931 inaugural lecture upon becoming director of the Institute for Social Research in Frankfurt (founded in 1923). He proposed an interdisciplinary research program combining philosophy and social theory with psychology, political economy, and cultural analysis (Horkheimer 1931). In that way, “social philosophy” aims at providing an encompassing interpretation of social reality as a whole – as “social totality,” to use a concept central to the Marxist tradition (Jay 1984).

Other key figures of the first generation include Theodor W. Adorno, Herbert Marcuse, and Walter Benjamin, along with Erich Fromm, Friedrich Pollock, Leo Löwenthal, Franz Neumann, Otto Kirchheimer, and figures like Siegfried Kracauer, who belonged to the broader circle for a few years (for rich historical accounts, see Jay 1973, Buck-Morss 1977, Dubiel 1978, Wiggershaus 1986, Wheatland 2009). The work of the largely Jewish members of the first generation was deeply marked by the rise of National Socialism, the experience of exile, and, for some of its inner circle, their return to Germany after 1945. After the Nazis closed the Institute, Horkheimer, who had already moved it to Geneva, re-established it at Columbia University in 1934, where he was soon joined by Pollock, Marcuse, and Löwenthal, while Adorno did not emigrate to the US until 1938. Horkheimer, Adorno, and Pollock moved the Institute from New York to Los Angeles in 1941. Those three reestablished the Institute in Germany after the War, with Horkeimer as director from 1951 to 1958 and Adorno from 1958 to 1969. Key figures who worked with first generation figures during this period emerged as the second generation: Jürgen Habermas, Alfred Schmidt, Albrecht Wellmer, Oskar Negt, and Claus Offe.

Habermas was the leading figure of this second generation, taking up Horkheimer’s chair in Frankfurt in 1964 before moving to a research post in Starnberg in 1971. Habermas returned to Frankfurt in 1981, retiring from this position in 1994. Axel Honneth worked closely with Habermas in the 1980s and took over the chair in social philosophy in Frankfurt in 1996; Honneth was also director of, and largely responsible for the revival of, the Institute for Social Research in Frankfurt from 2001 to 2018. He is considered a leading figure in the third generation, along with Seyla Benhabib, Nancy Fraser, and Christoph Menke (Anderson 2000, Allen 2010). Going beyond the second and third generations of the Frankfurt School, there are far too many figures to list; and the focal points for critical theory in this tradition have expanded, both geographically – with prominent figures in the United States and an active reception in Latin America – and thematically – for example, with a turn to feminism (see §4.1.1 ).

The first generation of the Frankfurt School took inspiration from an earlier generation of critical theorists: “Left Hegelians” in Germany who, after Georg Wilhelm Friedrich Hegel’s death in 1831, applied his philosophy critically to social and political phenomena like religion and the state, maintaining that the progressive realization of freedom in history that was central to Hegel’s thought was not yet complete and required a fundamental transformation of the status quo. Karl Marx became the most influential of this group. In a materialist transformation of Hegel’s thought, Marx analyzed the concrete conditions for realizing autonomy for all and viewed philosophy itself as conditioned by socioeconomic developments. By developing a critique of political economy in order to analyze the nature of capitalism and the possibilities for revolutionary social transformation, Marx set the standard for future generations of critical theory by combining radical philosophy with a critique of the best available social science of the day in the pursuit of emancipation.

Marx’s early writings, in the 1840s, were written when capitalist modernization was only just beginning in Germany, but he already saw contradictory social relations as the objective condition of capitalist society and exploited workers as a nascent revolutionary force. By the time the Frankfurt School began working out a critical theory of society in the 1930s much had changed as Germany had emerged as a leading economic power in an industrialized, capitalist Europe. Frankfurt School theorists were committed to social transformation, but the vehicle for change Marx identified – workers in advanced capitalist states like Germany – not only lacked revolutionary consciousness, but would soon embrace fascist politics when faced with economic crisis and mass unemployment. Radical social theorists would need revised analytical tools.

To study the psychology of individuals and groups along with social and cultural influences on that psychology, they could not rely on the then-dominant dogmatic versions of scientific Marxism (Pensky 2019). To understand how social conflicts get denied or repressed, and why individuals and groups turn to authoritarian politics that seem not to align with their class interests, they turned to Freudian psychoanalysis. In contrast to orthodox Marxism, they analyzed individual and group psychology, changes in the modern family, and the cultural “superstructure” of society, not just the material “base,” in order to understand how the rise of “mass culture” and the decline of authority figures in the family led to the decline of critical capacities both in the individual psyche and in society generally. This effort to combine Marx and Freud is one of the distinctive features of the Frankfurt School; exactly how to integrate psychoanalytic theory into critical theory has been a long-standing debate (Marcuse 1955, Whitebook 1995, Honneth 2010, Part IV; Allen and O’Connor 2019, Allen 2021).

In addition to incorporating insights from Freud’s psychoanalytic theory, early critical theorists drew on Max Weber’s social theory to analyze contemporary society. Crucial here was Weber’s theory of rationalization, which stressed the growing dominance of instrumental rationality, or means-end reasoning, through the expanding bureaucratization of society. Weber posited a loss of freedom, due to the “iron cage” of modern bureaucracy, and a loss of meaning generated by the “disenchantment of the world” associated with secularization. Weber’s work was crucial for Horkheimer and Adorno’s critique of instrumental reason (1947) as well as for Habermas’s later theory of communicative action (1981).

In synthesizing Marx and Weber, the first generation of critical theory was heavily influenced by Georg Lukács’s attempt to do the same in his ground-breaking 1923 essay “Reification and the Consciousness of the Proletariat” (see Brunkhorst 1983). Radically extending Marx’s analysis of commodities by analyzing how they transform the character of society as a whole, and drawing on Weber to describe a process of rationalization that extends to all aspects of life, Lukács used the term “reification” (see 3.2 below) to describe how the commodity form transforms the consciousness of those living in capitalist societies, who then see all social relations, even their relation to themselves, as taking on a “thing-like” character.

The classic philosophical influences on the Frankfurt School range widely, from Immanuel Kant and German Idealism to Nietzsche. In some form, Kant’s appeal to Mündigkeit (autonomy, maturity, responsibility) in his famous essay “What is Enlightenment?” – with its call for freely and publicly making use of reason – animates the ideal of emancipation throughout the work of the Frankfurt School, along with the Kantian conception of the critique of reason: the use of reason to reflect on the limits of reason. But its adherents follow Hegel and Marx in focusing on the social, cultural, and material conditions for achieving autonomy and insisting that reason is always socially and historically embedded. For first generation critical theorists, this entailed a critique of Kant’s own individualist and repressive understanding of autonomy as it arises within capitalist social conditions (Horkheimer 1933) and formalizes the domination of our own inner nature (Horkheimer and Adorno 1947, Excursus II, Adorno 1963a, Chs. 10–11). Some later critical theorists have engaged more positively with Kant, as in Habermas’s attempt to “detranscendentalize” core aspects of Kant’s transcendental philosophy (Habermas 2005, Ch. 2) and Rainer Forst’s Kantian constructivism in moral and political theory (Forst 2007, 2021a).

Hegel’s work has been a continual reference point for Frankfurt School philosophers, with key figures in the tradition – from Marcuse (1941) and Adorno (1963b) to Benhabib (1986, Part I) and Honneth (1992, 2001, 2011) – contributing both substantive studies and relying on Hegel’s methodology either for its holistic approach or as a paradigm of immanent critique while eschewing his metaphysical, teleological, and reconciliatory tendencies. Honneth first built on Hegel’s account of the struggle for recognition and the intersubjective conditions for living an autonomous life (Honneth 1992) before developing his own account of the practices and institutions of modern ethical life that realize freedom in a way that goes beyond its liberal and Kantian interpretations (Honneth 2011). Rahel Jaeggi builds on Hegel’s method of immanent critique in her account of progressive social change as learning processes in response to problems, contradictions, and crises that arise from within ethically thick forms of life (Jaeggi 2014).

In aiming to explain irrationality, the first generation extended the critique of reason, going beyond rationalist philosophers like Kant and Hegel to figures like Freud and Nietzsche. They turned to Nietzsche in particular as a critic of modern bourgeois culture and the violent formation of individual subjectivity. Engagement with Nietzsche’s thought extends from early essays by Horkheimer (1933, 1936a) through Horkheimer and Adorno’s shift toward doing critical theory in a more Nietzschean spirit with the genealogy of reason in Dialectic of Enlightenment (1947), and Habermas’s more critical take on Nietzsche’s supposed irrationalism (1985, Ch. 3–4), to contemporary authors such as Menke, who returns to Nietzsche as a positive reference point in the critique of the repressive dimensions of the modern ideal of equality (2000) and for a genealogical analysis of the modern subject who demands rights (2015).

One way of categorizing work by later generations of the Frankfurt School is to note how, even when drawing on a range of theoretical resources, they give pride of place to the legacy of a particular figure like Kant, Hegel, Marx, or Nietzsche (often via Foucault), or how they combine approaches. For instance, Honneth and Jaeggi are more Hegelian while Forst is more Kantian, and Benhabib is, like Habermas, a Hegelianized Kantian, and Fraser draws heavily on Marx in recent work while Amy Allen and Martin Saar are influenced by Foucauldian genealogy. The latter is part of a broader engagement between the Frankfurt School and post-structuralism, ranging from the more critical (Habermas 1985) through the more sympathetic (Honneth 1985, Menke 1988, 2000) to attempts to combine deconstructive and reconstructive approaches to critical theory (McCarthy 1991; see also Fraser 1989).

It is not easy to capture key features of an intellectual tradition shaped by such a variety of influences, including multiple figures whose own thinking changed over time, and a body of work addressing a vast range of topics spanning from the 1930s to the present. The rest of this section outlines some of the main arguments and focal points of key texts by key figures. It is not meant to be exhaustive, but to identify influential methodological approaches, arguments, and themes that are indicative of the work of the Frankfurt School and still provide important reference points for contemporary debates.

One largely undisputed reference for defining Frankfurt School critical theory is Horkheimer’s 1937 essay “Traditional and Critical Theory,” in which he defines critical theory by contrasting it with traditional theories that take the existing social order as given. Social sciences do this, for example, when they model themselves after the natural sciences in attempting to descriptively mirror a given set of facts or establish law-like generalizations. The point is not that empirical social research is invalid, but that traditional theories fail to analyze the broader social context in which they are embedded. This form of “positivism” views science as a purely theoretical undertaking divorced from practical interests even while it actually serves a particular social function in relying on established concepts and categories in a way that reinforces dominant ideologies and power structures. In that way, the forms of knowledge production that we rely on for insight into the social order become obstacles to social change.

Critical theory, by contrast, reflects on the context of its own origins and aims to be a transformative force within that context. It explicitly embraces an interdisciplinary methodology that aims to bridge the gap between empirical research and the kind of philosophical thinking needed to grasp the overall historical situation and mediate between specialized empirical disciplines. Critical theory aims not merely to describe social reality, but to generate insights into the forces of domination operating within society in a way that can inform practical action and stimulate change. It aims to unite theory and practice, so that the theorist forms “a dynamic unity with the oppressed class” (1937a [1972, 215]) that is guided by an emancipatory interest – defined negatively as an interest in the “abolition of social injustice” (ibid., 242) and positively as an interest in establishing “reasonable conditions of life” (ibid., 199). “The theory never aims simply at an increase of knowledge as such,” but at “emancipation from slavery” (1937b [1972, 246]) in the broadest sense of eliminating all forms of domination. The critique of traditional social science was further developed by Adorno and Habermas in the so-called positivism dispute in German sociology (Adorno et al. 1969, Wellmer 1969) and Horkheimer’s model of critical theory continues to inform discussions about how social critique might be carried out today in a variety of contexts (Outlaw 2005, Collins 2019, 57–65).

Nothing epitomizes the Frankfurt School’s interdisciplinary approach to analyzing irrational elements of modern society better than their studies of authoritarianism, beginning with studies of German society in the 1930s and continuing with studies of the U.S. in the 1940s. This work combined philosophy, social theory, and psychoanalytic theory with empirical research.

The first substantial foray was Studies in Authority and the Family (Horkheimer 1936b), the product of five years of research carried out by members of the Institute as part of the research agenda outlined by Horkheimer when he became director in 1930. In an essay articulating the study’s theoretical framework, Erich Fromm argued that the “drives underlying the authoritarian character” are “the pleasure of obedience, submission, and the surrender of one’s personality” along with “aggression against the defenseless and sympathy with the powerful” (Fromm 1936 [2020, 39, 41]). A main concern of the Studies was that the nuclear family had lost the power it once had to counter other socializing forces, which could now more directly influence the individual, and that individuals who view the world as governed by irrational forces submit to powerful leaders who ease their feelings of powerlessness.

The focus on authoritarianism continued into exile, with Neumann and Kirchheimer focusing more on distinctly political phenomena such as law, the state structure, and competing political groups under the Nazi regime (see Neumann 1944, Scheuerman 1996). Neumann and Kirchheimer were the main legal and political analysts of the first generation, but were outside the inner circle and less influential on the trajectory the Frankfurt School took in the 1940s (see Scheuerman 1994 and Buchstein 2020 for attempts to revive interest in their legal and political analysis).

The work on authoritarianism that the Institute is most well-known for came with the publication of The Authoritarian Personality (1950), the result of research conducted by Adorno in collaboration with a team of psychologists at the University of California, Berkeley. The aim was to identify personality types that might be susceptible to authoritarianism, based not on explicit commitments to fascist political movements but on psychological characteristics and social attitudes (measured on an “F-scale”). The researchers posited that individuals with an authoritarian personality tend to exhibit traits such as rigid conformity to conventional norms, a tendency toward stereotypical thinking, a preference for strong authority figures and disdain for perceived weakness, a preoccupation with power and status, and a propensity for prejudice and hostility towards minority groups. The book explored the link between authoritarianism and antisemitism, highlighting the role of scapegoating and the projection of repressed aggression onto targeted minority groups.

The text was published in a series edited by Horkheimer, titled Studies in Prejudice , along with other innovative studies such as Prophets of Deceit: A Study of the Techniques of the American Agitator (1949), a psychoanalytic analysis of the rhetoric and tropes of American demagogues authored by Frankfurt School member Leo Löwenthal and Norbert Guterman. If The Authoritarian Personality studied the kinds of people potentially receptive to the messages of authoritarian leaders, Prophets of Deceit studied the content of the messaging itself. Adorno would later follow up on all these themes – both the form and content of fascist agitation and the social and psychological conditions under which it can succeed (1951b, 1967a).

The Authoritarian Personality had a major impact on the field of political sociology, inspiring a wave of similar studies and commentary. The recent resurgence of authoritarian populism has inspired renewed interest in Frankfurt School analysis of authoritarianism (see Section 4.2 below) in conjunction with publication of new editions of some of the classic texts along with previously untranslated work by Kracauer on totalitarian propaganda dating from the late 1930s (Kracauer 2013 [2022]) and a 1967 lecture by Adorno on “Aspects of the New Right-Wing Extremism” (Adorno 1967a [2020]).

One point of continuity between the studies of authoritarianism and Frankfurt School cultural analysis more broadly was the idea that “mass culture” was one of the powerful forces playing an increasing role in the direct socialization of individuals, a role that led to the “disappearance of the inner life” of the individual (Horkheimer 1941) and an increasing loss of the ability to imagine a world any different than the existing one. In its various forms, this general thesis was common to Horkheimer, Adorno, and Marcuse in their critiques of mass culture from the 1930s to the 1960s.

More generally, the Frankfurt School is known for its analysis of popular culture. By contrast to orthodox Marxist dismissal of cultural analysis for focusing on the less consequential “superstructure” of society, Frankfurt School theorists attentively analyzed the form and content of cultural objects along with the genres and modes of producing works of art and popular culture. In an early essay titled “Mass Ornament” (1927), Kracauer argued that analyzing the “inconspicuous surface-level expressions” of an epoch, by virtue of their “unconscious nature,” can disclose its “fundamental substance” and “unheeded impulses” (1927 [1975, 75]). Adorno would later maintain that “cultural criticism must become social physiognomy” (1951a [1967, 30]), a method he pursued in his interpretations of works of literature and music by interpreting the surface features and forms of various cultural artifacts in relation to underlying social conditions as a mode of disclosive critique.

The more pessimistic analysis of mass culture of Horkheimer, Adorno, and Marcuse can be distinguished from the more optimistic views developed by Kracauer and Walter Benjamin. Benjamin posited, in his famous essay, “The Work of Art in the Age of Technological Reproducibility” (1936), that the rise of technologies for mechanical reproduction, such as photography and film, led to the decline of the “aura” surrounding traditional works of art – the “authenticity” associated with the unique presence of the original in space and time – in part because it makes no sense to talk about the “original” version of a photograph. The resulting changes in perception and modes of collective experience and participation in cultural production could, Benjamin hoped, also bring about political forms of art and a more general democratization of culture. He contrasted this emancipatory potential of mass culture, through a politicization of aesthetics, with the aestheticization of politics under fascism (Buck-Morss 1992). Adorno expressed his disagreement in an earlier letter to Benjamin and in published work (Adorno 1936, 1938). As Wellmer puts it, “in technologized mass culture, Benjamin sees elements of an antidote to the psychic destruction of society, whereas Adorno regards it above all as a medium of conformism and psychic manipulation” (1985/86 [1991, 32–33]). While Benjamin placed hope in mass culture, Adorno saw it lying in the kind of autonomous art that resists reconciling subjects to their social world, instead offering a kind of “promise of happiness” in a transfigured future that lies beyond that social world (Adorno 1970, Finlayson 2015, Gordon 2023).

The critique of mass culture took its most dramatic form in the chapter on the “culture industry” in Horkheimer and Adorno’s Dialectic of Enlightenment (first circulated in 1944 and published in 1947). They introduced the term “culture industry” to underline the fact that “mass culture” is not something “the masses” spontaneously generate (Adorno 1967b [1991, 98]), but is manufactured using the same standardized and profit-oriented methods as any industrial production method. In this sense, culture is no longer a relatively autonomous realm of meaning (that might aim, at its best, at beauty, freedom, and truth) or source of critical awareness, but is thoroughly commodified by the “distraction factories” of the culture industry. “Cultural entities typical of the culture industry are no longer also commodities, they are commodities through and through” (ibid., 129). Entertainment replaces experience, numbing the audience’s capacity for critical thought and reconciling them to the status quo in a form of domination far more subtle than direct tyranny.

In this way, Dialectic of Enlightenment , which is perhaps the most influential text by Frankfurt School philosophers, analyzes two forms of mass society, fascist Germany and the United States, focusing primarily on the latter. Co-authored by Horkheimer and Adorno between 1939 and 1944 at the height of Nazi rule and World War II, the text opens with these lines:

Enlightenment, understood in the widest sense as the advance of thought, has always aimed at liberating human beings from fear and installing them as masters. Yet the wholly enlightened earth is radiant with triumphant calamity (1947 [2002, 1]).

The book is a genealogy of reason that traces its self-destruction from the dawn of human history to the present. Reason was supposed to liberate human beings. Instead, in the dominant form it takes as instrumental rationality, it has become the primary instrument of their domination. With reason taking this form, humans lose their capacity for critical reflection as their thinking is increasingly oriented solely toward self-preservation within a system in which they are powerless. “Thought is reified as an autonomous, automatic process, aping the machine it has itself produced, so that it can finally be replaced by the machine” (ibid., 19).

The root of the catastrophic dynamic lies not just with modernity or capitalism, but goes back to humanity’s earliest attempts to dominate nature. A core thesis of the book is that myth and enlightenment are entwined. The process of enlightenment began with the earliest attempts to overcome “mythic fear” as a way of explaining the unknown and mitigating threats from nature. This anthropological claim about enlightenment is combined with a historical claim about the Enlightenment and the rise of modern science and technology. This is when instrumental rationality truly comes to dominate, as means-end calculation is the kind of reasoning required for capitalist production and efficient bureaucracy. “Enlightenment is totalitarian” (ibid., 50), Adorno and Horkheimer argue; it subsumes everything under its dissolvent rationality. In this way, enlightenment reverts back to myth.

The book represents a shift away from the critique of political economy, indebted to Marx, to the critique of instrumental reason, indebted to Weber (Benhabib 1986, 149–163). Although this shift is sometimes attributed to the growing pessimism of its authors during National Socialism, it was also motivated by Pollock’s analysis of the shift from nineteenth-century liberal capitalism to “state capitalism”: increased intervention by the state into the economy meant that the primacy of the economy posited by Marx had been replaced by the primacy of politics (1941). This claim supported the focus in Dialectic of Enlightenment on the administered control of society by the state apparatus. The book paints a bleak picture of a society in which people live “totally administered lives” under the sway of efficient and calculating institutions. For the sake of self-preservation, they adapt themselves entirely to this apparatus. All the while the culture industry, as an “organ of mass deception,” keeps them entertained at the price of numbing their critical capacities, producing conformity, and undermining any sense of individuality or capacity for autonomy. The book also represents a shift away from the earlier idea of critical theory as interdisciplinary social theory, which could marshal the findings of empirical social science toward the practical aim of emancipation, and more toward speculative history. In the story they tell, the effects of domination are so ubiquitous that every form of scientific knowledge is corrupted.

If Horkheimer and Adorno’s Dialectic of Enlightenment was supposed to provide the grounds for a positive concept of enlightenment – as they maintained in its preface (1947 [2002, xviii]) – many critics have wondered what that is supposed to be (Wellmer 1983). Habermas would later argue that the authors needed to leave “at least one rational criterion intact for their explanation of the corruption of all rational criteria” in order to “set the normative foundations of critical social theory;” but they failed to do so (1985 [1987, 127–9]; see also Benhabib 1986).

Reappraisals of the text in recent decades range from defending its approach as a form of world-disclosive critique (Kompridis 2006) that reveals our familiar social world as pathological by using techniques like “rhetorical condensation” (Honneth 1998), to reading it as developing a dialectical conception of progress – not simply a history of decline – aimed at making us more aware of the inevitable entanglement of reason with power (Allen 2014, 2016), and attempts to build on the chapter on antisemitism, which analyzes its social function in providing a “release valve” that allows rage to be “vented on those who are both conspicuous and unprotected” (1947 [2002, 140]), thereby stabilizing domination by channeling potential resistance to social suffering into hatred of a group (Rabinbach 2000, Rensmann 2017).

Herbert Marcuse’s influential book One-Dimensional Man (1964) – best summarized by its subtitle, Studies in the Ideology of Advanced Industrial Society – can be read as an attempt to update Dialectic of Enlightenment in the form of a diagnosis of U.S. society and its perfected mechanisms of pacification and social control, ranging from art, sexuality, and politics to philosophy and the very act of thinking. Marcuse argues that all forms of critical thought and practice, having been wholly integrated into the wasteful, dehumanizing, profit-seeking, imperialist logic of advanced capitalism, are subsumed by one-dimensional ideology, a “flattening out of the antagonism between culture and social reality” (61).

Marcuse developed his influential concept of “repressive desublimation” to explain how the manipulated need for instant gratification has sanitized any transgressive forces within the domains of sexuality and art. Prior to the rise of the “affluent society,” art contained a transcendent capacity in the sense that it thought of, engaged with, and appropriated the idea of breaking out of the world in which one lived and embodied the hope for a better one to replace it. Within late capitalism, art has lost this critical aspect and dissolved into consumer culture and technological rationality, masking the “surplus repression” that shapes human instincts and needs in line with the functional requirements of social domination and the reproduction of the status quo.

Marcuse’s work has been criticized for its totalizing diagnosis of domination, his reliance on an objectivist account of human nature and needs, and the paternalistic or even authoritarian implications that possibly result from combining these two elements (Jaeggi 2014 [2018, 104–108]). Nonetheless, it has remained an important reference point for the critique of technology (Feenberg 2023a, 2023b, Fong 2016, Ch. 5) and of false needs, and of new right-wing forms of “repressive desublimation” that affirm the status quo in a transgressive mode (Brown 2019, 165–169). Regardless of how one today assesses Marcuse’s concrete analyses, his work exemplifies a tension that all critical theories have to address between the dominating forces of one-dimensionality and the possibility of breaking free of them.

First-generation critical theorists posited various responses to their own bleak diagnoses of society from the 1940s to the 1960s. Marcuse supported rebellious social movements in the 1960s and 1970s, in contrast to other leading representatives of critical theory who kept a conspicuous distance. In One-Dimensional Man , he placed hope for overcoming the repressive, one-dimensional society in a “Great Refusal” to abide by its norms, as carried out by the “substratum of the outcasts and outsiders, the exploited and persecuted of other races and other colors, the unemployed and the unemployable” (1964, 256). He later expressed solidarity with, and saw as examples of this refusal in, both the global student movement (1968, 119) and the feminist movement with its aim of overcoming dominant forms of aggressive masculinity (1974). He likewise praised counter-cultural movements for expressing sexual, moral, and political rebellion in a non-aggressive form of life that might generate a total change in values (1967). For Marcuse, emancipation involves a new morality that fulfills the vital needs for joy and happiness and encompasses an aesthetic-erotic dimension that is foreshadowed in alternative artistic tastes and new social and cultural practices. While Horkheimer and Adorno were less supportive of rebellious social movements, they did become important institutional figures and public intellectuals after their return to Germany (Müller-Doohm 2003, part IV; Demirović 2016). Adorno’s radio addresses in particular can be viewed as an attempt to educate the public for autonomy and so as a kind of response to their own bleak diagnoses of society.

But the core of Adorno’s response, from the early essay on the culture industry to his posthumously published Aesthetic Theory (1970), was to posit that “autonomous” or “authentic” art, by contrast to the products of the culture industry, maintains a utopian impulse insofar as it points beyond, and provides a moment of resistance to, the status quo. For example, atonal music by composers like Arnold Schoenberg generates dissonance in the listener by challenging the unity of the whole found in more harmonious music. Adorno maintained that such art, in challenging aesthetic norms and conventions, can provide aesthetic experiences that are resistant to the homogenizing forces of the culture industry. Critics of this turn to the aesthetic have wondered how this is supposed to provide a sound basis for a critical theory of society (Benhabib 1986, 222).

But one can argue that Adorno’s later work was an attempt to push against that kind of grounding for critical theory. The title of Adorno’s 1966 magnum opus, Negative Dialectics (1966a), refers to a methodology that takes from traditional Hegelian dialectics the emphasis on difference and mediation but abandons the attempt to overcome difference through a unifying synthesis. Instead, taking up an argument already developed in Dialectic of Enlightenment , Adorno argues that “identity thinking” and the “identity principle” have been at the basis of humanity’s destructive project of cognitive as well as practical domination of external as well as internal nature, thereby linking the philosophical to the social oppression of particularity. Adorno rejects “identity thinking” in favor of affirming the negative, namely “non-identity,” that is, the irreducible particularity of objects, experiences, and persons that cannot be subsumed under concepts.

This approach undermines the totalizing aspirations of theoretical systems in philosophy as traditionally understood. The struggle to recognize that which is nonidentical is not only an epistemological but also an ethical and political project that seeks to do justice to both the object and the subject of cognition in their irreducible individuality (Bernstein 2001). Linking epistemology and the philosophy of language to critical theory of society, this leads Adorno to reject not only Hegel’s affirmative synthesis but also Heideggerian ontology and Kantian dualism. Methodologically, Adorno explores alternative ways of thinking about how to use and develop philosophical concepts, taking up the Benjaminian notion of constellation and developing “critical models” in order to articulate the complexity of experience, and suffering, without reducing or constraining it. In Adorno’s view, negative dialectics is a form of immanent critique engaged in a dynamic and transformative process, as it “must transform the concepts which it brings, as it were, from outside into those which the object has of itself, into what the object, left to itself, seeks to be, and confront it with what it is” (Adorno 1957 [1976, 69]). In his cultural criticism and interventions in public debates, Adorno follows this paradigm by exploring how concrete experiences exemplify a form of social domination that is obscured by mass culture but also open up the possibility of transcending reified consciousness by articulating the internal contradictions within social reality.

Jürgen Habermas, who worked closely with Horkheimer and Adorno in the 1950s until he fell out of favor with Horkheimer for seeming too radical, inherited one of the central claims of the Dialectic of Enlightenment , namely that Enlightenment is inseparable from the self-critique of Enlightenment, while also insisting on the context-transcending force of reason embedded in everyday practice.

Two works from the 1960s established his status as a leading figure in the second generation: The Structural Transformation of the Public Sphere (1962) and Knowledge and Human Interests (1968b). In the former, Habermas provides a historical and conceptual reconstruction of the idea of the public sphere in which subjects recognize each other as equals, submit to the “force of the better argument,” and subject legislation to the public use of reason. Against the backdrop of its emergence in eighteenth-century European societies, Habermas identifies the internal contradictions of the public sphere under the conditions of capitalism and traces its decline under the combined pressure of mass culture and mass media that has gradually transformed a reasoning public into passive consumers – a claim consistent with the “culture industry” thesis.

Critics argued that Habermas’s historical narrative of decline presupposes highly idealized versions of public debate and a “reasoning” public – a public that has always in truth been fragmented by class, gender, and race-based domination – and neglects the political significance of a multiplicity of subaltern and non-official public spheres and counter-publics (Negt and Kluge 1972, Fraser 1990, Warner 2002, Allen 2012). Nevertheless, his critical analysis of a contemporary public of consumers as the objects of processes of de-politicization, commercialization, political manipulation, and refeudalization seems to have lost nothing of its relevance (Seeliger and Sevignani 2022). The claim that a robust and independent public sphere is crucial to a healthy democracy is central to Habermas’s later, systematic contribution to democratic theory in Between Facts and Norms (1992), and he continues to analyze recent transformations in the structures and modes of communication within the public sphere (Habermas 2006, 2021).

Habermas’s Knowledge and Human Interests (1968b) was an ambitious attempt to ground critical social theory as a form of inquiry aimed at fostering a distinct type of knowledge tied to a deep-seated human interest in emancipation. This was a return to Horkheimer’s methodological aims in “Traditional and Critical Theory” (1937), but with a novel set of arguments, such as Habermas’s claim that the method of critical theory can be illuminated by way of an analogy with psychoanalysis – “the only tangible example of a science incorporating methodological self-reflection” (1968b [1971, 124]). Like Horkheimer, Habermas was critical of the positivist understanding of science for failing to see the connection between specific kinds of inquiry and fundamental human interests. Habermas posited that both the natural sciences and the “human sciences” (interpretive social sciences and humanities) are grounded in distinct practical interests. The natural sciences are a reflective extension of “labor” (instrumental action), which is tied to the practical interest in material reproduction. The human sciences are a reflective extension of “interaction” (linguistic communication), which is tied to the practical interest in symbolic reproduction. Habermas distinguished “critique” or “reflection” as a third practice organized around the interest in emancipation, understood in terms of overcoming various forms of heteronomy, domination, and dependency.

In the early 1970s, Habermas largely abandoned this framework, based in an anthropology of knowledge, though he did continue to pursue some of its themes, and epistemological questions have remained central to his work in at least two domains: first, in his “postmetaphysical” (non-foundationalist and fallibilistic) understanding of philosophy as a form of critical reflection at the intersection between science and society (Habermas 1983a, Ch. 1) and, second, in his critique of naturalism, especially neuroscience as a form of positivism or scientism that absolutizes the observer’s perspective, thereby negating the irreducibility of the participants’ perspective and occluding the normative structure of interpersonal communication (Habermas 2005, Ch. 6).

Habermas increasingly came to the view that critical theory needed more robust social-theoretical and normative foundations, since, in his eyes, the totalizing critique of the first generation had proven to be self-undermining (1985, Ch. 5) and his own approach in Knowledge and Human Interests had conflated the reconstruction of invariant structures of communication (formal pragmatics) with the critique of the false consciousness of particular persons and societies (1973a). Habermas’s alternative path, after abandoning that methodological framework, was to focus on communicative reason in a two-volume magnum opus titled The Theory of Communicative Action (1981). By contrast with an instrumentalist understanding of reason and action, Habermas’s “communicative turn” starts from a reconstruction of the rational and normative potential of everyday interactions.

This turn involves a multidimensional paradigm shift, illustrating the theoretical ambition of Habermas’ enterprise. He develops a theory of communicative action and rationality that is anchored in everyday practices of communication, in which we raise validity claims whose normative dynamic is context-transcendent and which allow for consensus-based coordination of action. He provides a historical reconstruction of modern rationalization processes, in which social integration via authority or shared tradition has been increasingly replaced by an expanded use of communicative reason in response to the pressure to cooperate. Finally, he constructs a two-level model of society based on the distinction between “system” and “lifeworld,” claiming that the regulation of coexistence in modern societies depends on both communication oriented towards mutual understanding (“lifeworld”) and on the anonymous systems of state bureaucracy and the capitalist market (“system”).

For the methodological renewal of critical theory, Habermas’s central claim is that within complex societies, social order always has a double form: It must simultaneously be viewed as lifeworld and as system. The lifeworld can only be understood from the hermeneutic perspective of its participants while the mechanisms of systemic integration only come into view from a system-theoretical or external perspective. Critical theory needs both perspectives in order to identify distorting effects of the system on the lifeworld. Habermas famously and controversially diagnoses a “colonization of the lifeworld” by the systemic media of money and power, which impose economic and administrative rationality – the main forms of “functionalist reason” – on areas of the lifeworld whose reproduction relies on communicative processes of cultural reproduction, social integration, and socialization that cannot be subsumed under the media of money and power without generating resistance. This provides a new foundation for critical theory by updating the critique of reification in the form of a critique of systematic distortions of communication. The “critique of functionalist reason” becomes a central task for critical theory, along with the aim of diagnosing the “selective pattern” of capitalist modernization that only partially realizes the actually available potential for rationality and learning within society.

In the ensuing discussion, Habermas was accused of reifying the “system” by conceptualizing the capitalist market and the bureaucratic state as functionally necessary and supposedly norm-free systems that lie beyond the theoretical reach of critical social theory and the political reach of emancipatory politics (Honneth and Joas 1991), of idealizing the lifeworld in ways that largely ignore the domination and exploitation of women and minorities (Fraser 1985), of subscribing to a progressivist theory of modernization and history that is Eurocentric and insensitive to the continuing effects of colonial domination (Allen 2016, Ch. 2), and of underestimating how deeply power penetrates into and distorts the very heart of communicative reason (Allen 2008, Chs. 5–6).

Habermas and his followers insist that while these phenomena are real, it is only the power of communicative reason – and the public discourses and deliberations in which it manifests itself and gets institutionalized – that allows us to detect, criticize, and ultimately overcome (if only partially and temporarily) those forms of domination. Whether one agrees or not that the communicative turn enables critical theory to analyze and bring to agents’ attention the distortions that block them from addressing and overcoming obstacles to emancipation, one important legacy of Habermas’s theory can be seen in opening up space for a methodologically pluralist critical theory in response to the fundamental need to capture the perspective of both participants and observers (Bohman 2003). Some Frankfurt School theorists have also built on Habermas’s system-lifeworld distinction in maintaining that social change must be viewed from the perspective of both “evolution” and “revolution” (Brunkhorst 2002, 2014).

One dominant story told about the Frankfurt School begins with Horkheimer’s original research program in the 1930s and views Horkheimer and Adorno’s radical departure from that vision in Dialectic of Enlightenment (1947) as an intellectual dead end from which Habermas rescued the tradition and returned it to its original methodology. From this perspective, the second generation, dominated by Habermas, superseded the first (see Kompridis 2006, 255–258, for a critique of this story). An alternative story would point out that Dialectic of Enlightenment was in many ways consistent with themes first articulated by Adorno in work from the 1930s – particularly his 1931 inaugural lecture, heavily inspired by Benjamin – that ultimately came to fruition in Negative Dialectics (1966a). To complicate matters in another way, while collaborating on Dialectic of Enlightenment in the 1940s Adorno also contributed to the interdisciplinary collaboration that culminated in The Authoritarian Personality (1950), a product of Horkheimer’s original vision for critical theory that combined social theory with empirical research.

Rather than viewing the second generation solely in terms of Habermas overcoming deficits in the first, this alternative story recognizes that there have always been multiple models and styles of critical theory operating simultaneously within the tradition ​​and that Adorno was heavily influenced by Benjamin prior to collaborating with Horkheimer (Buck-Morss 1977, Wolin 1994, 166, 265–274). Moreover, Adorno’s influence is evident in work by figures in the second generation such as Albrecht Wellmer (1933–2018), who used Adorno’s work as a basis for challenging Habermas’s approach (Wellmer 1985/86, 1993) and was far more sympathetic with post-structuralism than Habermas – also true of Wellmer’s students in the third generation, Christoph Menke (1988, 2000) and Martin Seel. Adorno scholars have defended his work directly against Habermas’s criticisms (Cook 2004, O’Connor 2004: 165–170), and critical theorists continue to defend Adorno’s approach to critical theory (Allen 2016, 2021, 175–183, Marasco 2015, Ch. 3).

To complicate the story further, Benjamin’s work has had an enormous influence on work by a variety of critical theorists, though his wider influence had to wait until Adorno collected Benjamin’s essays for a German audience in 1955 and Hannah Arendt edited them for English readers in 1968. There have been significant studies of Benjamin’s work by scholars working within the Frankfurt School tradition (see Buck-Morss 1989 and Pensky 1993), while many critical theorists beyond the Frankfurt School have engaged Benjamin’s critique of linear notions of progress, and the ways in which they fail to break with the catastrophic continuity of the present (Benjamin 1940, see Löwy 2001), as well as his analysis of the constitutive relation between law and violence (Benjamin 1920/21; see the recently published critical edition, 2021), to mention only Jacques Derrida’s “Force of Law” (1990), Giorgio Agamben’s Homo Sacer (1995), and Judith Butler’s Parting Ways (2012) (see also Loick 2012).

Methodological debates within the Frankfurt School focus not only on the legacy of first-generation theorists but also on Habermas’s earlier work, with some arguing that Knowledge and Human Interests is worth revisiting because it was more attuned than his subsequent work to the dynamics of power and domination, making it more apt for addressing oppression based on gender (Allen 2008) or race (McCarthy 2004), or for developing a more comprehensive critical theory of domination (Klein 2020). Honneth (2017) has recently taken Habermas’s text as a jumping off point for refocusing critical theory on the task of elaborating the relation between emancipatory interests and emancipatory knowledge. Honneth nonetheless maintains that Habermas’s use of the methodology of psychoanalysis as a model for emancipatory critique is not apt, while others argue that it is still in many ways productive (Celikates 2009 [2018, 137–157]; see Allen 2021, Ch. 5 for a critique of Habermas, Honneth, and Celikates).

The latter debate is part of the resurging interest in psychoanalysis by some theorists working in the Frankfurt School tradition. Habermas’s own engagement with Freud and psychoanalysis in Knowledge and Human Interests was largely methodological in contrast to the substantive use of Freudian ideas by the first generation (in their analysis of the entanglement of reason and repression and the concrete forces of fascism and antisemitism), and Habermas (1983a) subsequently abandoned psychoanalytic theory entirely in favor of engagement with developmental psychologists like Jean Piaget and Lawrence Kohlberg. In developing his theory of recognition, Honneth (1992, Ch. 5) returned to psychoanalysis in the form of object relations theory, primarily in the work of Donald Winnicott, arguing that the experience of fusion and symbiosis that characterizes the early infant-mother relationship is foundational in two ways: It serves as the template for the type of recognition Honneth calls “love” and explains why individuals and groups continue to experience existing relations of recognition – that necessarily fall short of fusion and symbiosis – as unsatisfactory and continue to struggle for recognition. While Honneth’s use of Winnicott is controversial (McAfee 2019, Ch. 2; Whitebook 2021, Deranty 2021), recent debates have more generally focused on how to take up object relations within critical theory (Allen and O’Connor 2019). As a result, the divide now seems to be primarily between those who focus on the pro-social implications of psychoanalytic theory (Honneth 2010, Part IV) and those who also stress asocial or antisocial forces of Freud’s drive theory in general and the death drive in particular in order to avoid what they see as the risk of over-idealization and romanticization built into Honneth’s way of integrating psychoanalysis into his theory of recognition (Allen 2021, Ch. 5). Those critics advocate returning to the more negativistic approaches familiar from first-generation critical theorists (Fong 2016, McAfee 2019, Allen 2021).

Honneth’s return to the question of struggles oriented by emancipatory interests (2017) hearkens back to a shift that began in the 1980s, when a significant strand of Frankfurt School critical theory, including Honneth’s early work (1985), aimed at recovering the connection between theory and practice by linking the development of theory itself to social conflicts and movements. Oskar Negt and Alexander Kluge’s Public Sphere and Experience (1972) is an early example of a critique of the bourgeois (i.e. hegemonic) public sphere that invokes proletarian or plebeian non-state forms of the public and the divergent critical experiences they articulate as alternative sources of normativity, while also identifying blockages they face in the form of the “consciousness industry” and the pacification of social conflicts through “pseudo-publics.”

In a more explicit vein, Nancy Fraser contributed to the feminist turn in Frankfurt School critical theory – for which the work of Seyla Benhabib, Jean Cohen, and Amy Allen has also been decisive – in echoing Marx by arguing that critical theory should frame its “research program and its conceptual framework with an eye to the aims and activities of those oppositional social movements with which it has a partisan, though not uncritical, identification” (Fraser 1985, 97), and that the Frankfurt School in general and Habermas in particular had failed to theorize one of the most significant struggles against domination: the feminist movement (see §4.1.1 ).

Honneth has also sought to systematically reconstruct the link between theory development and struggles by taking experiences of misrecognition that lead to social struggles for recognition as a pre-theoretical reference point (1992). Drawing on a wide range of philosophical work, psychological and psychoanalytic accounts of identity-formation, and sociological and historical accounts of social movements struggling for recognition, Honneth has developed a theory of recognition that is the most prominent alternative paradigm, within Habermasian critical theory broadly construed, to Habermas’s theory of communicative action (Honneth 2000, Zurn 2015). Honneth maintains Habermas’s focus on intersubjectivity, but instead of linguistic practice and the ideal of “undistorted communication,” he focuses on relations of mutual recognition and the ideal of “undistorted recognition,” which then serve as the basis for the critique of “social pathologies” that he considers central to the project of critical theory (Honneth 2004).

In short, the Frankfurt School of critical theory is today constituted by lively debates, discussed more below, about how to deploy various critical methods ( Section 2 ) and concepts ( Section 3 ) while remaining attuned to social struggles and crises ( Section 4 ) and positioning itself in relation to critical theories developed out of other traditions.

2. Critical Methods

Frankfurt School critical theory is best characterized by a set of methodological aspirations that set it apart from many other forms of social and political theorizing (both in philosophy and the social sciences): It aspires to be (1) self-reflexive , accounting for its own embeddedness in specific social and historical conditions, (2) interdisciplinary , integrating philosophical analysis with social theory and empirical social research, (3) materialist , grounding critical theorizing in social reality, and (4) emancipatory , orienting itself toward the goal of social emancipation. These commitments situate the Frankfurt School firmly in the Marxist tradition, and that tradition’s aim of overcoming the division between theory and practice without uncritically subsuming one under the other.

This has given rise to three interrelated methodological challenges: how to conceptualize (1) the relation of theory to social reality, (2) the role and standpoint of critical theorists, and (3) the normative foundations, content, or force of their critical theorizing. In light of historical developments in the first half of the twentieth century – the rise of fascism and Stalinism and the integration of the working class into the liberal welfare state – Frankfurt School theorists lost confidence in an identifiable direction of history or an identifiable collective subject like the proletariat to lead the way. It became increasingly unclear how to uphold a link between their theories and a pre-theoretical anchor within social reality – such as oppositional experiences, forms of consciousness, practices of resistance, or social struggles and movements – or even to see how the conditions for any of those things to emerge were present at all.

Against this backdrop, this section first sketches the common ground most Frankfurt School theorists find in the approach of immanent critique ( §2.1 ) before tracing the various ways in which they have sought normative foundations ( §2.2 ) in a more or less constructive or reconstructive ( §2.3 ) register, then turns to methods such as disclosive and genealogical critique that are critical of those normative approaches ( §2.4 ), and concludes by outlining a set of methodological challenges that shape contemporary debates ( §2.5 ).

In responding to the three-pronged methodological challenge of relating theory to social reality, reflecting on the standpoint of critique, and spelling out its normativity, Frankfurt School critical theory moves beyond the usual juxtaposition between internal and external critique. Frankfurt School theorists rely on a third model of critique, which builds on Hegel and Marx and is often understood as immanent or reconstructive. Critique proceeds immanently or reconstructively when it seeks to secure its normative resources and epistemic standpoint from the (often implicit) normative structures and epistemic possibilities of the practices and self‐understandings that are constitutive of the (type of) society in question. Immanent critique avoids the dichotomy between an internal critique that refers to standards and standpoints that are already recognized by those criticized and an external critique that refers to standards and standpoints that are not (or not yet) recognized and therefore have to be derived independently from the agents’ perspective and their social context (see Jaeggi 2005, 2014, Celikates 2009, Stahl 2013a). Critical theory understood in this way is both grounded in social reality as it exists and emancipatory in seeking to radically transform this reality.

The critique of ideology can both serve as a paradigmatic example of immanent critique in this sense and illustrate some of the challenges this model faces (Ng 2015). Ideology critique is immanent insofar as it starts from the contradictions of a social and ideological constellation and the experience of those affected, which is shaped by these contradictions. It does not criticize an ideological form of consciousness because it is immoral or unethical, but because of its epistemic, functional, and genetic features, i.e. for being false or distorted, for contributing to the reproduction of relations of domination, and for arising from within such relations in ways that are relatively immune to self-reflection. Consequently, the critique of ideology does not focus primarily on the injustice or domination found in society, but on the forms of consciousness, culture, practice, habit, and affect that make this injustice or domination seem natural or unavoidable (Jaeggi 2008). On this view, any critical theory that aims at emancipation must first aim at diagnosing and overcoming those obstacles that keep agents from fully experiencing, critically reflecting on, and collectively acting against the unjust and dominating conditions under which they live. The question is how critical theorists can do so without falling back into epistemologically and politically problematic distinctions between false and true consciousness, between ideology and scientific insight, and between true (“objective”) and false (“purely subjective”) interests and needs (Celikates 2006; see Section 3.3 below).

These challenges are among the many challenges critical theorists face in developing an immanent critique that is linked to social reality and practice, a link that comes out in two ways. First, theory is anchored in social reality in terms of its genesis, as it is shaped by the social context from which it emerges. Second, theory aims at a practice that transforms social reality. This dual commitment to linking theory and practice is spelled out in two rather different ways, both in the history of the Frankfurt School and in contemporary discussions. One way of anchoring theory in social reality – call it the crisis approach – starts with social contradictions, antagonisms, and crises, along with the practical challenges and conflicts that result, and maintains that identifying those conflicts requires socio-theoretical analysis and sociological research (Jaeggi 2017a, Fraser and Jaeggi 2018). A second way of anchoring theory in social reality – call it the struggles approach – takes social struggles and movements and the practices of critique and resistance of oppressed groups as its starting point. This approach incorporates alternative standpoints and counter-hegemonic epistemologies into its theorizing with the aim of countering the potentially disempowering and anti-emancipatory effects that arise when critical theorists view crises mainly in terms of structural contradictions while ignoring or underestimating the ways that social and political movements themselves can produce and intensify crises (Collins 2019, Celikates 2022).

While this distinction between crisis and struggle is useful for heuristic purposes, it should not be overstated. Most critical theorists share a commitment to the emancipatory role of theory as well as an immanent anchoring of theory in social reality, whether qua crises or struggles. The distinction is a matter of degree and starting points, and it is usually agreed that crises and struggles stand in need of mutual articulation (see Benhabib 1986, 123–133, and Section 4.1 and Section 4.2 below).

Horkheimer maintained that a critical theory should not have an external relation to, but must enter into a “dynamic unity” with, practice, so that it is “not merely an expression of the concrete historical situation but also a force within it to stimulate change” (1937a [1972: 215], see also Marcuse 1937, Horkheimer 1937b). But under social conditions that neutralize social struggles or turn them into regressive backlash movements, the “dynamic unity” envisaged by Horkheimer can appear foreclosed. Even for Adorno, whose diagnosis of the “totally administered world” is the most radical example of this foreclosure, however, it would be a mistake to conceptualize existing society as a perfectly closed, monolithic, and functionally integrated self-reproducing totality. Rather, even when society is viewed as a totality, it has to be understood not in terms of homogeneity or frozen stability but in terms of structural antagonisms (Adorno 1957 [1976, 77]), conflict, and process (Adorno 1966b), i.e. as riddled with contradictions that, at least in principle, allow for forms of oppositional experience, consciousness, or practice that a critical theory can build on. In one of his last texts written shortly before his death, Adorno concludes that “critical theory is not aiming at totality, but criticizes it. This also means, however, that it is, in its substance, anti-totalitarian, with the utmost political determination” (Adorno 1969a; our translation). Even – or especially – in the face of the closure of political space, the political significance of a critical theory can consist in safeguarding the link between theory and the possibility of a radically different practice. At the same time, this defense of the relation to practice needs to be complemented by a defense of theory in the face of what Adorno identified as an “actionist” and anti-theoretical ideology of “pseudo-activity” in arguing that “praxis without theory, lagging behind the most advanced state of cognition, cannot but fail, and praxis, in keeping with its own concept, would like to succeed” (Adorno 1969b [1998, 265]).

Despite this more nuanced reading of Adorno on the relation between theory and practice, the broader diagnosis – put forth in different guises by Adorno, Horkheimer, and Marcuse – that social integration, the pacification of class conflict, and the internalization of conformist attitudes had robbed critical theory of any pre-theoretical anchor, provides an important background for Habermas’s break with the first generation. That break concerns not only their “pessimism,” but the basic methodological and substantial premises of their theories. In Habermas’s view, the first generation had navigated themselves into a dead end with their totalizing diagnosis of an all-encompassing state of delusion dominated by instrumental rationality. In response, and in order to provide firm normative foundations for critical theory, Habermas advocates a “communicative turn,” reformulating social critique in terms of a critique of the conditions of communication and grounding it in the normative content presupposed within the practice of linguistically mediated social interaction and argumentation.

This element of normative validity – as opposed to merely factual social validity that is forced, imposed, or presupposed – is elaborated in Habermas’s discourse theory, originally referred to as “discourse ethics” (Habermas 1983a, Ch. 4) but later evolving into a differentiated approach that distinguishes between ethical and moral norms (Habermas 1991) and a discourse theory of law and democracy (Habermas 1992). At the heart of discourse theory is a principle of discursive justification that Habermas refers to as the “discourse principle” or “D,” which states: “just those norms of action are valid if all persons affected could agree as participants in rational discourse” (Habermas 1992 [1996, 107]). He further specifies discourse theory with a universalization principle (“U”) that is operative when arguing about moral norms, and a democratic principle that is operative when attempting to justify legal norms within a democratic society. Habermas does not naively suggest that actually existing discourses correspond to these ideals, but maintains that in those discourses participants necessarily make idealizing presuppositions that can then be used to identify and criticize the shortcomings of actual discourse as distorted by interests, power relations, and ideologies.

As a response to the challenges of immanent critique outlined above, Habermas’s work can be understood in terms of a “dialectics of immanence and transcendence” (Cooke 2006, Ch. 3). Habermas maintains the need to situate reason historically and within social reality – the largely Hegelian, pragmatist, or reconstructive element of his thought. But the idealizations that are immanent in our linguistic practices point toward context-transcending validity claims that must be defended in a discursive procedure – the Kantian or constructivist element in his thought. Habermas now refers to his attempt to “de-transcendentalize Kant” as a form of “Kantian pragmatism” (Habermas 1999; see also Bernstein 2010, Ch. 8; Baynes 2016, Ch. 4; Flynn 2014b).

Some interpretations of Habermas stress that his theory of communicative action is still a form of immanent critique (Finlayson 2007, Stahl 2013b) while others object to his increasingly Kantian focus on moral norms (Heath 2014). To provide empirical confirmation of his rational reconstruction of the “moral point of view,” further situating it within social reality, Habermas drew on Kohlberg’s developmental moral psychology, itself decidedly Kantian in its defining the highest stage of moral development in terms of the ability to make universalizable moral judgements (Habermas 1983a, Ch. 4; for a critique, see Benhabib 1992, Chs. 5–6, which, drawing on Carol Gilligan’s critique of Kohlberg, distinguishes a “generalized other” from a “concrete other” whose experience cannot be accounted for by abstract conceptions of the moral standpoint).

Habermas’s shift toward a Kantian position is particularly evident in the Rawls-Habermas debate (Habermas 1995a, Rawls 1995, Habermas 1996), widely viewed as a “family quarrel” among two Kantian political philosophers. In his early work on discourse ethics, Habermas compared his own principle (U) to Rawls’s “original position,” arguing that his approach was the better way to “operationalize” the moral point of view as a form of moral constructivism that tests moral norms in a discursive procedure posited as a dialogical alternative to Kant’s categorical imperative (Habermas 1991). The debate shifted in the 1990s with their contributions to legal-political constructivism: Rawls’s Political Liberalism (1993) and Habermas’s Between Facts and Norms (1992), in which he provides a rational reconstruction of the institutions of constitutional democracy. In that context, Habermas argues that Rawls’s approach is not transcendent enough, since in Habermas’s view Rawls reduces normative validity to the notion of reasonableness immanent within liberal democratic societies (for the implications of their debate for multiple issues in moral and political philosophy, see Hedrick 2010, Baynes 2016, Chs. 6–7, and Finlayson 2019).

Habermas’s Kantian turn also came to the fore when extending his work in a cosmopolitan or “post-national” direction (beginning with Habermas 1995b), even if he has continued to combine a Kantian approach to justifying universal norms with a wide-ranging analysis of the empirical phenomena of globalization (1998). This combination of normative and empirical theorizing, a hallmark of the Frankfurt School, is present in a range of work by other critical theorists addressing global issues (Ingram 2019, Ibsen 2023), from the challenge of disaggregating citizenship from the nation-state (Benhabib 2004) to transnationalizing the public sphere (Fraser et al. 2014), and theorizing new forms of transnational democracy (Bohman 2007). Rather than simply defending abstract cosmopolitan norms, such approaches typically aim at some form of critical cosmopolitanism (Milstein 2015), with some stressing the crucial role of political contestation of allegedly universal norms “from below” (J. Ingram 2013) or of concrete struggles for rights as part of a broadly construed intercultural dialogue on human rights (Flynn 2014a).

In light of Habermas’s turn to Kant, a significant focus of debate among Habermasians and interpreters of Habermas has been the status of idealizing presuppositions and the ultimate status of the principles of justification within discourse theory. Defenders of discourse theory can be divided up into those who focus more on immanence – pointing in a Hegelian, pragmatist, contextualist, or reconstructive direction – and those who focus more on transcendence – pointing in a Kantian or constructivist direction. Among the former, some argue, echoing Hegel’s critique of Kant, that Habermas should situate reason more thoroughly within its social and historical context in order to avoid an overly rationalistic, abstract, or gendered approach (Benhabib 1986, 1992), while others have argued for Habermas to embrace a more pragmatist (McCarthy 1991, Bernstein 2010) or contextualist approach (Rorty 1985, Allen 2008, Ch. 6). Habermas’s most recent work (2019) attempts a kind of middle path, going in a decidedly historical direction by tracing the provincial, European origins of his “post-metaphysical” mode of theorizing as a preparatory stage to a fully inclusive, global intercultural dialogue as the way to establish its universal validity in a world characterized by “multiple modernities” (see Forst 2021b, Chambers 2022, and Flynn 2022 for critical assessments).

Those who have taken discourse theory in a more Kantian or transcendental direction include Habermas’s long-time interlocutor Karl Otto-Apel, who argued that the dynamic of universal validity claims in practices of argumentation transcendentally presupposes an ideal communication community from which universal normative foundations for the assessment of discourses can be derived (Apel 1985). Apel maintained that grounding reason, and thereby critique, requires a more transcendental justification (or “ultimate grounding”) than Habermas has provided (Apel 1989; see Habermas’s most recent reply to Apel in 2005, Ch. 3).

More recently, Rainer Forst has embraced Kantian constructivism in positing that every human being has a “right to justification,” a right to demand reciprocal and general reasons for the practices, institutions, and structures that affect them (Forst 2007). Forst views moral and political constructivism as distinct, but integrated stages. While the task of moral constructivism is to construct a list of basic moral rights that cannot be reasonably rejected, those abstract rights must be given concrete content by citizens in a process of political constructivism. He maintains that his approach is immanent insofar as the right to justification is “recursively grounded” by reconstructing the validity claims implicit in all morally justified claims, while maintaining a moment of transcendence since the right to justification can be justifiably claimed in any context. Forst views this as the normative core of a critical theory that understands society as an ensemble of practices of justification. In that sense, the concept of justification is both descriptive (referring to actual arguments given within a particular social order) and normative (referring to reasons that could or should be accepted), and Forst maintains both perspectives are needed for a critique of existing justification narratives and relations of justification (see the Introductions to Forst 2011 and 2021a).

Various critics of Habermas have argued that his normative turn and shift to Kant risks transforming critical theory into something that looks increasingly like a liberal theory of justice. They posit alternative approaches such as reconstructive, disclosive, and genealogical critique that also return to questions and arguments developed by the first generation.

Those who subscribe to the model of reconstructive critique emphasize the downsides of uncoupling normative argument from social analysis and social theory. In Axel Honneth’s work, this shift takes two forms. In his earlier work (1992), he argues that the relatively narrow rationalist focus on communicative reason occludes more fundamental and often prelinguistic experiences and intersubjective relations that give rise to struggles for recognition and that his Hegel-inspired theory is better able to articulate, thus reestablishing the link between theory and social reality in more substantial ways. Relatedly, Honneth insists that critical theory can be distinguished from other normative enterprises by its reference to “the pretheoretical resource in which its own critical viewpoint is anchored extra-theoretically as an empirical interest or moral experience” (Honneth 1994 [2007, 63–64]).

Expanding on this earlier commitment, in his later work Honneth argues against the division of theoretical labor in which (constructivist) philosophy engages in normative theorizing while empirical sociology investigates our social reality (2011). By contrast, he undertakes a “normative reconstruction” of how modern society – its legal, moral, political as well as social and economic practices and institutions – came to be centered around individual freedom as the highest value of this cultural formation. Honneth wants to show that we can only gain an adequate theoretical understanding of, and critical perspective on, modern society if we analyze its different social spheres as attempts to institutionalize the value of freedom. In contrast to both revolutionary and conservative approaches, he wants to show that the structure of this institutionalization allows for a progressive realization of the value of freedom as social actors appeal to the constitutive idea of freedom to challenge the concrete forms of unfreedom that remain characteristic of our social reality.

Similar to Honneth methodologically, Rahel Jaeggi argues, in her reconstructive approach to the critique of forms of life, that bracketing the question of how to rationally evaluate and criticize forms of life as a whole, as Rawlsians do in the name of liberal neutrality and Habermasians in the name of “ethical abstinence,” ends up hindering precisely the kind of experimental learning processes that are crucial for forms of life to remain dynamic and avoid stagnation and failure (2014 [2018, 9–24, 318–319]). But Jaeggi places a greater emphasis on contradictions, crises, and conflicts than the later Honneth (see also Schaub 2015).

The approaches of both Honneth and Jaeggi exemplify a conception of immanent critique that closely links analysis and critique, issuing in a critique that is neither a mere description of what exists nor a normative demand imposed on what exists from the outside. Accordingly, it does not proceed in a free-standing, normative way, but relies on a specific combination of philosophical reflection and social-theoretical as well as empirical research that is grounded in social developments and crises and actual social experiences and self-understandings. This methodological reorientation has also led to a more substantial engagement with questions of the economy and the sphere of work, both from a more Durkheim-inspired (Honneth 2022, 2023, Celikates, Honneth, and Jaeggi 2023) and a more Marx-inspired (Fraser 2022) position that has also resulted in a fundamental (non-reformist) critique of capitalism (Fraser and Jaeggi 2018).

While these approaches seek to develop a socially grounded form of normativity, critics argue that they are still too idealizing in their understanding of social reality and its historical genesis, as well as too normative in their methods from the point of view of yet another model of critique, which has been called disclosive or genealogical.

Disclosive critique typically takes its cue from Adorno (and sometimes other theoretical sources from Heidegger to contemporary aesthetics), moving beyond the dichotomy between literary world-disclosure and philosophical reason-giving or the quest for normative foundations. On this view, critique has the task of revealing the world in a new and different light, disclosing unrecognized suffering and intricate forms of domination that are not only occluded by dominant ideologies but also shape the norms that emanate from that order in ways that escape more strongly normative versions of immanent critique that build on them. Dialectic of Enlightenment can be read as an exercise in disclosive critique that seeks to defamiliarize the social world for its readers and thereby break open their unquestioned acceptance of how things appear to them (Honneth 1998).

This negative orientation of disclosive critique can be complemented by a more positive one, in which what is disclosed also involves potentialities and horizons that have no space or way to articulate themselves within the existing social and normative order. Walter Benjamin’s writings on the radical potential of mass culture or Judith Butler’s Gender Trouble (1990) can be seen as examples of disclosive critique that involve both the disruption of established and the experimental opening up of new experiences and schemas (Vogelmann 2016).

Some critical theorists attempt to integrate a more positive idea of disclosure into critical theory while maintaining that this is not at odds with expanded conceptions or normativity. Some draw on Heidegger to develop an account of world-disclosive critique that rethinks reason and agency, stressing receptivity and “self-decentering” as an alternative model to Habermas’s focus on procedural reason (Kompridis 2006). Others stress that while disclosure can and must be subject to intersubjective validation through argumentation, critical theory must have recourse to the disclosive power of imagination, which is revealed in the force of exemplarity (Ferrara 2008), in focusing attention on the aesthetic dimension of narratives that social movements use to imagine alternative possibilities (Lara 1998, 2021), or in the way that powerful representations of the good society function to disclose a transcendent object that cannot be fully known or represented but can nonetheless provide ethical orientation (Cooke 2006). In a variety of different ways, these approaches attempt to maintain the utopian dimension of critique (Marcuse 1937).

Genealogical critique, by contrast, can be seen as a form of disclosive critique that is more focused on problematizing, unmasking, and disrupting (Saar 2002, Koopman 2013). Given its association with Nietzsche and Foucault, it also has a distinct trajectory, set of methodological commitments, and theoretical implications. Taking aim at social practices, self-understandings, identities and normative commitments that are seen as natural or accepted as given, genealogical critique traces their historical emergence, highlighting their contingency and denaturalizing them with the aim of opening up the possibility of thinking and acting differently. From this perspective, the search for normative foundations is misguided as it both underestimates how normativity is shaped by unacknowledged histories and power relations and overestimates the transformative power of a normative critique that appeals to reason alone. Genealogical critique, by contrast, seeks to destabilize and decenter the subject and its fundamental commitments (Owen 2002, Hoy and McCarthy 1994; for a version of this claim that builds on psychoanalytic theory, see Allen 2021, Ch. 5).

While earlier engagements with genealogical critique, especially Foucault’s, were marked by criticisms of his supposed rejection of all normative and rational standards, lack of social theorizing, and relativism (Habermas 1985, Chs. IX–X, Fraser 1981, Dews 1987), more recently critical theorists have sought to emphasize the potential convergence and mutual illumination of genealogy and Frankfurt School critical theory in providing an analysis of the workings of contemporary forms of power and domination (Allen 2008, Koopman 2013, Ch. 7, Saar 2018). At the same time, a recent debate between Forst and Wendy Brown exemplifies how the earlier split between Habermas and Foucault is rearticulated today, with Forst taking a broadly Habermasian position in arguing that his “respect conception of tolerance” manages to safeguard the autonomy of individuals by grounding toleration in the right to justification, and Brown insisting, with Foucault, on the normalizing, disciplining, and depoliticizing effects of liberal discourses of toleration that ultimately obfuscate the complex operations of social power (Brown and Forst 2014, see also Vogelmann 2021).

A genealogical orientation also characterizes postcolonial critiques of Frankfurt School critical theory that point out the lack of explicit and sustained engagement with European colonialism and imperialism and its legacies, including contemporary forms of racism, and the ways in which these have enabled and shaped the processes of “modernization” and thus the formation of “modern”’ societies, subjects, and forms of knowledge and rationality, all of which critical theorists purport to investigate critically (see §4.1.3 below).

Exponents of genealogical critique and struggle-centered approaches problematize forms of immanent or reconstructive critique that take institutional achievements as their starting point, challenging them by excavating the histories of domination and repression, as well as struggles, that have constituted these institutions and continue to shape their functioning. This gives rise to numerous challenges that continue to animate methodological debates in critical theory: (1) how (or even whether) to defend the putative normative achievements of liberal democracies, and if those are to be defended as achievements, then (2) how to theorize about the relation between struggles, crises, and institutional achievements, in contexts that may involve either (3) an absence of struggles, or (4), the opposite problem, a proliferation and fragmentation of struggles:

From the perspective of genealogical and post-colonial critique, the commitment to the institutions of the modern liberal nation-state (Habermas 1992, Honneth 2011) relies on an idealizing view of the history and present of this political formation that ignores, or treats as historically contingent and philosophically inconsequential, the forms of domination and exclusion that have accompanied it. At a time when the putative institutional achievements of liberal democracies – such as the separation of powers, the independence of the judiciary, the integrity of elections, or the protection of fundamental rights, especially for minorities – have come under attack from right-wing and neo-authoritarian movements and governments, the question is how critical theorists can defend the normative achievements of the existing order despite its systemic shortcomings. Offering a more radical challenge, some critical race theorists and post-colonial critics argue that those shortcomings reveal that what were thought to be normative achievements were historically premised on, and continue to functionally presuppose, domination and exclusion both at a societal and global level (see §4.1.2 and §4.1.3 below). On a methodological level, this involves the challenge of revising or going beyond the normative and sociological categories of critical theory that seem, at least in part, to be tied to a specifically Western experience.

Many critical theorists who accept the claim that these are normative achievements insist that a more complex view of the relation between institutions, struggles, and crises is necessary. As mentioned above, an alternative strand within critical theory that reaches from Negt and Kluge’s recovery of proletarian counterpublics through Fraser’s theorization of feminist movements to current attempts to reconnect critical theory with the struggles of our age, has insisted that abstracting from collective movements and struggles and relocating the emancipatory potential in the normative achievements of the existing institutional order risks underestimating how institutional dynamics, the inherent crisis tendencies of (more or less) liberal democracies, and social struggles are inextricably intertwined. Beyond a merely historical and social-theoretical point, how this question is answered will also affect how to conceptualize the role of emancipatory as opposed to regressive struggles in the face of the new authoritarianism (see §4.2.3 below).

More abstractly, critical theorists must account for situations in which there seem to be no struggles or forms of critical consciousness to latch onto, or only highly constrained forms of them. How can a critical theory respond to a situation in which domination is more or less total and has managed to suppress any critical consciousness and practice? Some of Marcuse’s descriptions of contemporary society come closest to this scenario. One might respond that “a society of happy slaves, genuinely content with their chains,” a society in which domination is experienced not as domination but as freedom, might be the critical theorists’ nightmare, but it “is a nightmare, not a realistic view of a state of society which is at present possible” (Geuss 1981, 83–84). Nevertheless, the challenge points to a dilemma critical theorists need to navigate. On the one hand, a critical theory requires a starting point in the forms of consciousness, experience, and practice of its addressees, but, on the other hand, critical theory should respond to and address distortions and blockages of precisely these forms of consciousness, experience, and practice. While these distortions and blockages will in most cases turn out to be partial rather than total and thus allow for some form of problematization to emerge (Celikates 2009, Part III), it seems equally important to not simply tie a critical theory to already existing social movements and thus to “goals that have already been publicly articulated” since this “neglects the everyday, still unthematized, but no less pressing embryonic form of social misery and moral injustice” (Honneth 2003, 114; see also Renault 2004, 2008).

The opposite problem can arise when critical theorists diagnose a proliferation of social struggles and lines of conflict beyond the classic antagonism of labor and capital. After the demise of the kind of philosophy of history that identified the proletariat as the revolutionary subject and the workers’ movement as the emancipatory force to which critical theory could and should attach itself, it has become unclear how critical theorists can determine with which of the different emancipatory movements of their day to enter into the kind of alliance envisaged by Marx and Horkheimer and which “forms of existing social critique” or “experiences of injustice” to pick up on. This difficulty is not only due to the plurality – or intersectionality – of movements, practices of critique, and experiences of injustice, but also due to the fact that struggles are often far from perfectly aligned and can operate at cross-purposes, with regard to both their aims and their methods. In answering this challenge, critical theorists can neither simply deduce the “correct” struggle from some overarching laws of historical development (the pole of determinism), nor claim that theorists simply have to decide which struggle or movement to link their theory to (the pole of voluntarism).

Insofar as critical theory is committed to immanent critique, focusing on the internal contradictions and crises of a specific social order and the struggles and movements that arise from within it, these challenges cannot be easily resolved. Rather than seeking to resolve them at an abstract level, they could instead be viewed as opening up a field of tensions that critical theorists need to navigate within the specific constellation they find themselves in. While critical theory needs to be anchored in actually existing forms of theoretical as well as practical critique, in the social struggles that people actually engage in, it also has the task of articulating the experiences of those who are blocked from engaging in struggles of their own and of contributing to the further theoretical articulation of existing struggles. At times, critical theory may need “to push beyond the ‘subjective’ elements of struggle and languages of claims-making to the more ‘objective’ dimensions of contradictions and crises, which turn more on the dynamics of systemic elements operating independently of whether or not people actually thematize them via struggle” (Fraser and Jaeggi 2018, 11), without losing sight of the epistemic and political risks this involves.

In addressing these risks, one way forward has been to embrace methodological pluralism and to understand critical theory less as a comprehensive social theory and more as a critical practice, as something critics do (Bohman 2003, Kompridis 2006, Celikates 2019a). This approach can more systematically incorporate alternative standpoints and epistemologies and the practices of epistemic resistance they are tied to, and more easily build on other traditions and paradigms of critical theory, such as feminist, anti-colonial, and anti-racist struggles and theorizing (Mills 1988, Collins 1990, 2019, Medina 2013, Loick 2021, Celikates 2022; see Section 4.1 below). Anchoring the perspective of critical theory within the social struggles and epistemic standpoints of the oppressed can serve as a counterweight – in the sense of “reflexive accountability” (Collins 2019) – to the tendency of actually existing critical theories to set in motion a disempowering spiral of epistemic asymmetries that denies the existence of theoretically sophisticated practices of critique and resistance on the ground and thereby reproduces existing obstacles to equal participation in knowledge production and to radical social transformation. On this view, critical theorizing is itself a social practice that recognizes its addressees as equal partners in a dialogical struggle for appropriate interpretations and realization of transformative potentials that is informed by social theory and sociological research. As such, it can make use of a variety of critical methods – reconstructive, constructive, disclosive, or genealogical (Freyenhagen 2018) – that are not easily subsumed under one unified metatheoretical framework, even if they can be seen as various attempts to spell out the idea of a critical theory as self-reflexive, interdisciplinary, materialist, and emancipatory.

3. Critical Concepts

The basic concepts of Frankfurt School critical theory – such as alienation, reification, ideology, but also emancipation – are expressive of the specific methodology, or set of methodologies, that critical theorists in this tradition employ. As explained in the previous section, critical theory in this tradition proceeds in an immanent way, and this implies that its concepts are both developed from within a certain social constellation and seek to go beyond the self-understanding characteristic of this constellation, they are both descriptive and evaluative, and they exemplify the unity of analysis and critique inherited from Marx. While some concepts are primarily “anticipatory-utopian” (like emancipation) and others primarily “explanatory-diagnostic” (like alienation, reification, and ideology, as obstacles to emancipation) (Benhabib 1986), they are all “thick concepts” whose descriptive content is irreducibly social-theoretically as well as evaluatively loaded.

In addition, some of the critical concepts developed by Frankfurt School authors – again alienation, reification and ideology are the clearest examples – point to second-order phenomena. In contrast to substantial first-order injustices, these concepts seek to critically diagnose what happens when unjust (or exploitative or oppressive) social relations are not experienced as unjust (or exploitative or oppressive) but are accepted as legitimate or natural, or if they are intuitively experienced but not explicitly recognized as such, or recognized but not adequately interpreted and articulated. These concepts pick out social phenomena that are often ignored by more mainstream approaches in moral and political philosophy that focus on the moral status of the individual and their actions, or the legitimacy of institutional arrangements, to the neglect of the domain of the social, with its distinct structure, dynamics, and challenges (see, e.g., Honneth 2000, Ch. 1, Zurn 2011, Neuhouser 2022, Ch. 1). The following subsections introduce four key concepts that exemplify both the critical methodologies discussed in the previous section and the substantial social-theoretical and diagnostic contributions to our understanding of contemporary society that Frankfurt School critical theory aspires to. There are of course other concepts used by critical theorists – from normativity, justice, and autonomy to power, domination, and oppression – but the focus here is on concepts less widely discussed in other traditions or to which Frankfurt School theorists have made distinctive contributions.

The concept of alienation has a long history within critical theory. The basic concept refers to the idea of humans being separated, estranged, or distanced from something crucial to their freedom or capacity to flourish. One is alienated when one has a distorted or deficient relation to oneself or to the natural or social world. Critical theorists face a number of challenges in developing a critique of alienation. Classic critiques of alienation, Rousseau and the early Marx for example, relied on substantive conceptions of human nature or self-realization to ground their diagnoses and provide standards for critique. Thick accounts of human nature are less compelling today, which means contemporary critics of alienation have pursued alternative approaches. Since a critique of alienation attempts to diagnose a social pathology, not a problem with particular individuals, critical theorists must also provide a social theory that can convincingly diagnose the social causes of, and possible paths for overcoming, alienation.

Rousseau can be credited with inaugurating “social philosophy” as a domain of inquiry while developing a critique of alienation (Honneth 2000, Ch. 1). Although he does not refer to alienation in his “Second Discourse” (1755), the term captures his argument that living in society leaves human beings disconnected from their true desires and passions, which he explored by speculating about what humans would have been like in a state of nature. Within Hegelian and Marxist social criticism, the concept of alienation has been used to capture the idea that something produced by humans is wrongly taken by them as something given or outside their conscious control (Jaeggi 2005 [2014, 13–14]). In his Phenomenology of Spirit (1807), Hegel first develops a concept of alienation to describe the relation of the human mind to reality when the products of human reason are not recognized as our own creation but are instead experienced as alien forces. In his Economic and Philosophical Manuscripts (1844), Marx analyzed how wage labor within capitalist societies causes alienation. Workers produce a world of objects, but the products of their labor as well as their own productive activity are commodities over which they have no control; the world they create becomes an alien power with increasing control over them. They are alienated from the kind of spontaneous and creative productive activity that Marx, in his early work, posits as the essence of human nature.

The concept of alienation was influential among first-generation Frankfurt School theorists, particularly in the work of Marcuse and the later work of Erich Fromm (1961). In Dialectic of Enlightenment , Horkheimer and Adorno echo Rousseau in telling a story of alienation going back to the dawn of civilization. They maintain that human beings, in their quest to dominate the natural world (external nature) and to acquire mastery over themselves (inner nature), become estranged from both aspects of nature, failing to see what Enlightenment denies: that we are fundamentally natural beings (Vogel 1996, 69).

Contemporary critical theorists have attempted to rejuvenate the concept of alienation without relying on overly substantive accounts of human nature and without the totalizing diagnosis of Dialectic of Enlightenment . Rahel Jaeggi formalizes key elements of the Hegelian-Marxist approach in developing a philosophical account of alienation focused on how failure to adequately appropriate oneself or the world results in a “relation of relationlessnes” (2005). In this way, the non-alienated self is not defined by a substantive conception of human nature but by the quality of one’s relation to the world: whether this relation is sustained by successful processes of appropriation. Hartmut Rosa also defines alienation as a distorted relation to the world but with a more substantive approach to the quality of non-alienated relations to the world. For this, he has developed a multifaceted concept of “resonance” to capture a kind of vibrant or responsive relation to the world by contrast with the alienated experience of the world as ossified, mute, or hostile (2016). In contrast to these approaches, which are largely framed in terms of necessary conditions for living a good life, Rainer Forst has argued that deontological aspects of the critique of alienation have been neglected, and that there is a kind of “noumenal alienation” that results from not being recognized, or failing to recognize oneself, as an agent of justification (2017).

Reification is a concept with close ties to alienation. If alienation is viewed as diagnosing a distorted relation to the world, reification can be understood as one way of articulating the form that distortion can take. In the broadest sense, reification is a term used to critique cases in which some entity that should not be viewed as an object – oneself, other people, or some segment of the social or natural world – is treated as a thing-like object. It is instrumentalized, objectified, or quantified in a way that is inappropriate according to some critical standard. One challenge for critical theorists is articulating the standard or perspective – a non-reified relation or perspective – according to which the reified stance is not appropriate.

Georg Lukács’s classic 1923 essay on reification heavily influenced the Frankfurt School. Lukács combined Marx’s analysis of the “fetishism of commodities” – which causes social relations between human beings to appear as quantifiable and thing-like – with Weber’s analysis of bureaucracy – which extends this instrumentalizing attitude to all social domains. Reification becomes “the necessary, immediate reality of every person living in capitalist society” (1923 [1971, 197]), which can refer to an instrumentalizing attitude taken toward objects (whose qualitative feature are reduced to quantitative terms), other people, and features of one’s own personality when viewed solely from the perspective of their marketability.

Different critical theorists have appealed to the concept of reification to capture similar but not identical phenomena, with differing definitions corresponding to differences in the larger theoretical framework in which they deploy the concept. For Horkheimer and Adorno, the concept captures the dominance of instrumental reason and the totally administered world that results (1947). Habermas reinterpreted the concept to describe the ways in which systems such as the economy and the bureaucratic state, which function properly as spheres in which instrumental rationality dominates, extend too far into spheres of everyday life that he refers to as the lifeword (1981). This “colonization” of the lifeworld by the system results in the communicative structures of the lifeworld becoming reified. Honneth, by contrast, takes up the concept of reification in relation to his theory of recognition, arguing that reification involves a kind of forgetting of a primary relation of mutual recognition that he calls “empathetic engagement” (2005). Within Rosa’s theory of resonance, in which he attempts to capture one side of the history of modernity as a “catastrophe of resonance,” reification can be viewed as a “forgetfulness of resonance” (2016 [2019, 325]). The revival of this concept has been extended in other ways by using reification as a guiding concept for analyzing the relation between economics and subject formation within a “political economy of the senses” (Chari 2015) or pairing reification with a suitably modified notion of reconciliation to assess experiences of exclusion and integration within modern social orders (Hedrick 2019).

Ideology is similar to alienation and reification in being both a concept critical theory inherits from the Marxist tradition and one that is used to identify a distorted relationship to the world and one’s own place in it (Eagleton 1991). In the Marxist tradition, it has played a prominent role in answering questions such as why people accept social and political conditions that seem to be contrary to their own interests, or how it is possible that subjects feel free although they are dominated. When people experience and describe relations of exploitation and domination as natural and without alternative or even as just, this seems to be an effect of ideology. Ideology, on this critical understanding, usually denotes a more or less coherent system of action-guiding beliefs, such as liberal individualism, that is said to obscure social reality – especially power relations, crisis tendencies, and social conflicts. As Marx (1844, 1846, 1867) and subsequent critical theorists argue, by obscuring these, ideology contributes to the reproduction of the prevailing order (Rosen 1996). Accordingly, any radically transformative and emancipatory practice presupposes that this ideological obfuscation must be recognized as such, criticized, and overcome. The challenge to such critical reflection is particularly acute when the possibility of even asking questions about how we might want to live, if we could transform society, is occluded by a technocratic ideology that reframes such practical questions as technical problems with narrow solutions (Habermas 1963, 1968a).

Ideology differs from mere deception, propaganda, or conspiracy theories. Because it is structurally anchored in social reality and plays a functional role for its reproduction, it cannot be explained with reference to the individual psyche or manipulation by others alone. Even if false consciousness is an element of ideology, critical theorists from Adorno to Jaeggi emphasize the practical nature of ideology as it shapes identities, is embedded in social practice, and functions via affects and habitus.

According to one influential interpretation, the critical notion of ideology developed in the Frankfurt School is characterized by three dimensions (Geuss 1981, Jaeggi 2008). In the first, epistemic dimension, ideologies always encompass epistemically deficient beliefs and attitudes that can range from substantially false beliefs to the confusion of particular and universal interests and inadequate concepts (such as “illegal alien” to refer to undocumented immigrants). In the second, functional dimension, ideologies are seen as playing a necessary, or at least supporting, role for the stabilization and legitimation of social relations of domination, i.e. for their more or less smooth reproduction. In the third, genetic dimension, ideologies are shaped, in ways that are not transparent to the agents themselves, by the social conditions under which they emerge, so that it is not an accident that people end up with the specific sets of beliefs they end up with in a specific type of society.

Radicalizing the Marxist notion of ideology as “necessarily false consciousness,” i.e. consciousness that is false (and not simply morally problematic) for structural reasons (and not just accidentally), Adorno and Marcuse often seem to argue that ideology reaches into the innermost core of subjects, who are shaped all the way down to their psychological and physical impulses, leading them to affirm the existing order and thereby preempting any resistance to domination. While this might help explain the resilience of ideology and its continued effectiveness, it also poses the challenge for critical theorists to find an anchor for their critique in the forms of consciousness, experience, and practice of its addressees (Celikates 2006, and Section 2.5 above).

Due to its emancipatory orientation, the critique of ideology must connect up with the self-understanding of those affected by trying to initiate learning processes, which in turn are supposed to lead to a transformation of those social conditions that are hidden behind ideologies. At the same time, without recourse to critical theories agents themselves will often continue to face obstacles to identifying, diagnosing, and explaining the effects of ideology on their critical capacities and practices. Arguably, showing that a contradiction is inscribed in the existing social order and can only be “dissolved” if this order itself is fundamentally transformed is also a task for a critical theory.

Although for most critical theorists ideology is not merely false consciousness but embedded in social practices and identities, ideology critique has been criticized for being overly cognitivist and underestimating the role of habitualized attitudes and cultural practices, for relying on an overly strong distinction between true and distorted consciousness, and for presupposing an idealized notion of the subject. Critics such as Foucault and Bourdieu speak instead of power-knowledge (Foucault 1973, 15) or of symbolic power and its embodiment (Bourdieu 1980, Ch. 8). The epistemological and political challenges the notion of ideology gives rise to continue to animate discussions (Celikates, Haslanger, and Stanley (eds.) forthcoming), including, more recently, on the relation between ideology and epistemic injustice (Fricker 2007, Mills 2017), cultural technē (Haslanger 2017a), and propaganda (Stanley 2015).

Frankfurt School critical theory inherits its emancipatory orientation from Marx, in the sense that it aims not only to understand, but also to contribute to a radical transformation of the social world that is already under way, and the commitment to real emancipation as requiring a radical, irreducibly social and political transformation that overcomes the fundamental contradictions of modern society instead of partial or local reforms aimed at surface-level symptoms. Emancipation is thus understood as liberation, including self-liberation, from domination by social, political, and economic powers, both personal and structural. Against this background, however, critical theorists have given different accounts of what emancipation is, what it requires, and how much can be said about it as a process and as an aim or state. While some (Horkheimer 1937a, Habermas 1968b) have thought of emancipation as a process of enlightenment and self-reflection that would allow for the realization of a rational organization of society, others thought of emancipation as sensual liberation (Marcuse 1969), or as emancipation from the (internalized) destructive imperatives of capitalism towards a state “of lying on water and looking peacefully at the sky” (Adorno 1951c [2005, 157]).

At the same time, and insofar as the working class has been integrated, fragmented, or at least reconstituted, it has become increasingly less clear who is to be emancipated (or self-emancipated) from which forms of domination and how. The challenges to the possibility of emancipation include reflections on the potentially overblown ideals of autonomy, sovereignty, and transparency that seem to underlie it (Laclau 1992), the limits of active self-transformation under conditions in which subjects have been shaped by power-ridden forms of subjectivation (Allen 2015), and the prospects of overcoming capitalism given the apparent lack of any clear and viable alternative. Today, critical theorists also face the challenge of reorienting the emancipatory project in the face of a catastrophic climate crisis that seems to privilege adaptation, mitigation, and sheer survival over utopian visions of emancipation that have also served historically as a pretext for an extractive and dominating relation to nature (Brown 2022).

In light of these challenges, a critical theory that wishes to hold on to its emancipatory orientation will need to articulate emancipation as an immanent possibility that is enabled and in some ways required by unprecedented historical developments. Whether in doing so it can build on the presumption of an emancipatory interest of the oppressed that theorists from Marx and Horkheimer to Habermas and Honneth (2017) have sought to identify remains contested. But thinking of emancipation as a second-order process that aims at enabling collective practices of self-determination over and against the obstacles picked out by concepts such as alienation, reification, and ideology, rather than as a substantial ideal or positive utopian vision of emancipation to be attained, might provide a starting point. Insofar as critical theory continues to see the existing social order as one of structurally entrenched domination, exploitation, and alienation, it will also continue to rely on some notion of an emancipatory process that points beyond those structures, even if this process is invariably plural, non-teleological, open-ended, and negative in orientation.

4. Critical Theories Today

Marx defined critical theory as the “self-clarification of the struggles and wishes of the age” (Marx 1843). The vitality of this approach to critical theory depends on continually taking up this task in new social contexts, as the first generation of the Frankfurt School did. Contemporary critical theorists continue this legacy by engaging with and theorizing in relation to contemporary struggles, crises, and practices. This has meant engaging a much wider range of emancipatory social movements than earlier generations of the Frankfurt School, who focused more on class struggle and capitalism (and the ways these were entangled with antisemitism and fascism) while largely neglecting issues like colonialism, racism, and the subordination of women. Contemporary critical theorists have expanded and enriched the Frankfurt School tradition by engaging with, and in some cases making contributions to, feminist theory, critical race theory, and postcolonial and decolonial theory (4.1), enlarging their analyses of crises beyond capitalism and its contradictions (4.2), and exploring a variety of critical practices ranging from civil disobedience to prefigurative, abolitionist, and revolutionary practices (4.3).

4.1 Theorizing Struggles and Movements

As emphasized above, Frankfurt School critical theory is methodologically interdisciplinary and defined by its aim of contributing to the emancipatory transformation of society by critically reflecting on the ways in which thinking itself can be distorted by structures of domination. This is also true of the various forms of critical theorizing that have emerged from and in relation to struggles against gendered oppression, racism, and colonialism and its legacies. Indeed, those critical theories bring to light structures of domination and modes of thinking (patriarchy, white supremacy, neocolonialism and Eurocentrism) that have until recently been neglected by the Frankfurt School and must be taken into account by any theory that aims to be critical and emancipatory.

More than one feminist theorist has argued that engaging feminism has been, and still is, crucial to renewing Frankfurt School critical theory both methodologically and in order to live up to its emancipatory aims (Fraser 1985, Ferrarese 2018). But analyzing the intersection between feminist theory and the Frankfurt School is complicated by the diverse array of theorists on both sides of that intersection. Some of the debates among feminist critical theorists mirror debates already discussed, for instance between those who draw on first generation versus Habermas or those who embrace Habermasian versus poststructuralist critical theory.

In most accounts, the first generation of the Frankfurt School is portrayed as not including any women and, with the exception of Marcuse in the 1970s (Marcuse 1974), its main protagonists largely failed to theorize about gender-based oppression or engage with feminist movements or the feminist theory of their time (there is, however, a new research project at the Institute for Social Research in Frankfurt that aims to challenge the dominant historiography by highlighting contributions of female researchers such as Käthe Weil and Else Frenkel-Brunswik and feminist work within the Frankfurt School). While fully acknowledging why feminists might find little of value in the first generation, some feminist theorists have highlighted important methodological affinities between, and potential for productive engagement with, that body of work (Brown 2006, Heberle 2006, Marasco 2006). In spite of the first generation’s nostalgia for the authority of the patriarchal family, their studies of authoritarianism were groundbreaking in analyzing the family as a political institution and breeding ground for fascism (Marasco 2018). Recent interest in Adorno’s work in particular builds on his theory of the nonidentical as support for the feminist critique of essentialist identities as well as affinities between feminist aims and his deconstruction of dualisms like nature and history or reason and desire, and his appeal to lived experience as crucial to philosophy and critique (Heberle 2006, 5–6). Attempts at synthesis include using his theory of the nonidentical, in dialogue with Lacan and Marx, to theorize a new approach to feminist political subjectivity (Leeb 2017), and combining Adorno’s insights into “bourgeois coldness” with the feminist ethics of care to rethink the fragility of our concern for others within a capitalist form of life that fosters “generalized indifference” while also producing a gendered form of attention to others (Ferrarese 2018).

Turning to the second generation, the critique of Habermas’s failure to adequately theorize gender in his Theory of Communicative Action (1981) was a turning point. In a now-classic essay, Nancy Fraser (1985) took a cue from the Marx quote about critical theory reflecting on the struggles of the age to criticize the Frankfurt School, and Habermas in particular, for failing to theorize one of the most significant struggles against domination. Seyla Benhabib raised similar concerns about whether the theory of communicative action could adequately theorize the feminist movement (1986, 252), and in Situating the Self (1992) aimed to make Habermasian discourse theory more cognizant of the self as gendered (see also the essays collected in Meehan 1995). In his later discourse theory of democracy, Habermas does engage the feminist theory and politics of equality to illuminate his core thesis about how private and public autonomy mutually presuppose each other (1992 [1996, 418–427]). But feminist critical theorists maintain that his rationalist approach fails to adequately capture the way power operates (Allen 2008, Ch. 5; McNay 2022, Ch. 1) or to incorporate forms of communication like narrative that have been crucial to feminism (Lara 1998, 2021; Young 2000).

The third generation of the Frankfurt School represents a crucial shift, with prominent feminist theorists like Fraser and Benhabib attempting to make critical theory more amenable to feminism from within the tradition, while also engaging in debates with leading figures in the poststructuralist strand of feminist critical theory like Judith Butler (Benhabib et. al. 1995). A core issue in these debates has been between Habermasian feminists who stress autonomy and poststructuralists who stress the idea of subjection – the ways in which power is central to the formation of subjects and their desires (Butler 1997). Amy Allen critically engages and synthesizes insights from both sides of this debate in viewing subjects as both constituted through relations of power and able to exercise autonomy in the form of critical reflection (Allen 2008). Axel Honneth, another key figure in the third generation, has engaged with feminist theory (Honneth 2000) and the feminist movement (2011 [2014, 154–176]), and in debates with feminist critical theorists including Fraser (Fraser and Honneth 2003) and Butler (Ikäheimo et al. 2021), but his work has also been the subject of sustained feminist critique of his conception of love, the family, and caring labor (Young 2007, Rössler 2007, Wimbauer 2023).

Fraser has, over several decades, developed a systematic defense of socialist feminism while charting various shifts in the feminist movement (see the essays collected in Fraser 2013), recently making the case that the contemporary crisis in care work must be understood as part of a larger general crisis in capitalist society (Fraser 2016, 2022, Ch. 3). Other feminist critical theorists also argue for a return to the critique of capitalism as crucial to feminist theorizing (Leeb 2017). From a different perspective, Lois McNay argues that recent Frankfurt School theorists, not only Honneth and Forst but also Fraser and Jaeggi, have failed to adequately incorporate the experience of gendered oppression into critical theory (McNay 2022). Another set of challenges arises from the need to develop an intersectional analysis of power and domination while engaging with a broader range of work in feminist and gender theory including queer and trans* theory as well as transnational and postcolonial feminism (Allen 2019, 537–538).

Apart from the influential studies on antisemitism and fascism by the first generation, Frankfurt School theorists have until recently shown little interest in issues of race and racism despite the prominence of anti-racist struggles and theorizing throughout the twentieth century and the present. The silence is of course not total. Early analyses point to prejudice toward Jews and other minority groups as an important part of the authoritarian personality and a key mechanism of providing “pseudo-orientation in an estranged world” (Adorno et al. 1950, 622), diagnose a culturalist transformation of the earlier biological racism at the center of fascism in post-war Europe that serves to maintain white supremacy (Adorno 1955, 148–9), and identify the phantasmatic dimension of racism and its fictions of homogeneity, purity, and essential difference (Adorno 1967a). Arguably, there are also broader methodological lessons from the relational and materialist theory of antisemitism developed by Adorno and Horkheimer that also hold for the study of racism (even if their relation remains contested, see Catlin 2023), namely the rejection of psychologizing and individualizing approaches, the insistence that the pathology always lies in the antisemitic or racist subjects and not in their victims, and the emphasis on structural factors that include the functional role of racism in the context of the crisis of capitalism and democracy (see Postone 1980 for an early attempt to explain modern antisemitism in relation to the nature of capitalism and the anti-capitalism of National Socialism).

Despite these openings, there has not been any sustained engagement with the phenomena of race and racism or with anti-racist struggles and theorizing, an eminently emancipatory form of knowledge production that, from W.E.B. Du Bois and Frantz Fanon to Black feminism (Collins 1990, 2019, Mills 2017), has been engaged in crossing the theory-practice divide and articulating dominated standpoints in ways that should have been of significant interest to Frankfurt School theorists (Outlaw 2005; for a relatively early exception see McCarthy 2009).

This missed opportunity is all the more astonishing as the intersection of class and race, of racism and capitalism has been at the center of theorists that share a Marxist orientation, and even some closeness to the Frankfurt School, most notably Angela Davis – who had studied with Marcuse in the US and with Adorno in Frankfurt, and, following Marcuse, insists on the need to bridge the gap between theory and practice and to combine the critique of racism as well as gender-based domination with a critique of capitalism (Davis 1983, 2004) – and Stuart Hall, who, building on Marxist and post-Marxist approaches, theorizes racism as a historically variable response to crisis and as a mechanism that allows capital to divide the working class (Hall 2021).

In contrast to the first generation’s focus on the “dark side” of modernity, later theorists, from Habermas to Honneth, developed a stronger commitment not only to Enlightenment values, but to the belief that these have been, more or less successfully, institutionalized in Western societies. As a result, their views clash with a core aim of Critical Race Theory (Crenshaw et al. 1995) – itself influenced by Marxist theories of the state and the law – namely, the aim of debunking the idea that the law and the state are neutral institutions that secure the common good and the rights of all as an ideology masking their character as instruments of racial (and class) oppression, as evidenced by massive and persistent inequalities that systematically disadvantage Blacks in the US in particular and racialized populations on a global scale, in various areas of life, from access to education, health, jobs, and housing to the risk of becoming a victim of police violence. According to this view, the forms of freedom and solidarity realized in liberal-democratic societies are not just contingently accompanied by exclusions of racialized groups, as if these values had only been insufficiently realized up to now and only need to be extended to those hitherto excluded. Rather, the thesis is that these exclusions have played a constitutive role in the history of these societies and their value systems and continue to shape them to this day, and that radical emancipation would therefore require developing entirely different visions of living together in freedom and solidarity (Kelley 2002).

More recently, Nancy Fraser (2022, Ch. 2) has picked up on Black Marxist discussions of racial capitalism (prominently Du Bois 1935) by arguing that capitalism provides a structural basis for racial oppression and thus exhibits an inherent (even if historically variable) tendency to racialize populations in order to more effectively expropriate and exploit them. Others have elaborated a relational and materialist understanding of racism that builds on how antisemitism was theorized in the early Frankfurt School, and how racism was rearticulated in a culturalist register in reaction to anticolonial and antiracist struggles (Balibar and Wallerstein 1991, Bojadžijev 2020). What these approaches share, and what might be a distinctive contribution of a critical theory of race and racism, is a commitment to understanding racism as a comprehensive social relation that needs to be understood in relation to broader (capitalist) social formations, “race” as an ideological effect rather than an unquestioned category for social analysis, and anti-racist struggles as a starting point for critical theorizing about race – commitments that are at least partially shared with important contributions in the critical philosophy of race (Mills 2003, Shelby 2003, Haslanger 2017b).

For all its focus on modes of domination in modern society, Frankfurt School critical theory has largely failed to address European colonialism and imperialism (Said 1993, 278) and their continuing effects in a world structured by massive inequalities and asymmetries between the Global North and the Global South. With a few recent exceptions to be discussed here, critical theorists in this tradition have not engaged much with the large body of postcolonial and decolonial theory, even if in recent years debates about the universal validity of human rights and cosmopolitanism, globalization and multiple modernities, religious pluralism and postsecularism, have provided ample occasion to go beyond still operative Eurocentric limitations and become more globally relevant (Mendieta 2007, Butler et al. 2011, Baum 2015, Ingram 2019, Kerner 2018; on some early Frankfurt School engagement with Chinese thought, specifically in Benjamin’s work, see Ng 2023).

The main target of postcolonial critique is the idea of a universal history in which the central engine of progress is located in modern Europe while non-Europeans are viewed as always lagging behind. The story has taken many forms, from narratives of progress in Enlightenment thinkers and their critics, such as Hegel (Buck-Morss 2009), to nineteenth-century theories of racial hierarchy and twentieth-century theories of development that have been shaped by, and in turn, rationalized, racism, slavery, and imperialism (McCarthy 2009, Bhambra and Holmwood 2021). Both anticolonial struggles and theorizing (in the work of Mahatma Gandhi, Aimé Césaire, Fanon and others) have insisted that the history and present of capitalism and of modern European and North American societies are constitutively entangled with colonialism, imperialism, and their afterlives, and that taking their trajectory as paradigmatically modern ends up representing a specific and heterogeneous trajectory and experience as universal and self-contained (Grüner 2010). While some aspects of postcolonial critique can be seen as overlapping with the critique of conceptions of the subject, reason, and universal history in the early Frankfurt School, the former also goes beyond the latter by understanding these as the effects of specifically colonial forms of domination and by tracing a different genealogy of fascism through its roots in the colonialism of the nineteenth century (Bardawil 2018).

Recent decades have seen attempts to bring postcolonial theory into dialogue with the Frankfurt School. From the side of decolonial theory, Enrique Dussel has been one of the most prominent decolonial philosophers to engage with Frankfurt School philosophers, developing a global ethics of liberation in critical dialogue with the discourse ethics of Apel and Habermas (Dussel 1998; see also Dusell 2011 and Allen and Mendieta 2021).

From the side of Frankfurt School critical theory, postcolonial critique has been taken up in a variety of ways (see also Vázquez-Arroyo 2018). In the same spirit of Horkheimer and Adorno’s attempt to critique enlightenment in the name of an alternative conception of enlightenment, both Susan Buck-Morss (2009) and Thomas McCarthy (2009) attempt to salvage something of the core idea that is the target of their critique: “universal history” for Buck-Morss, and “development” for McCarthy.

Amy Allen (2016), on the other hand, is more decidedly critical of the role of the discourse of “progress” and the role of such concepts in grounding normativity and shaping assumptions about historical development, modernization, and reason in the work of Habermas, Honneth, and Forst. She regards the latter approaches as deeply Eurocentric and contrasts them with a contextualist form of critique, inspired by Foucault and Adorno, that takes the form of a critical history of the present that uncovers the deep entanglement between reason and domination. Calling for an even more thorough revision of historical narratives, conceptual frameworks, and normative criteria, Gurminder Bhambra (2021) argues that the prevalent understanding of modernity as an endogenous European achievement obscures the fact that colonization and slavery were integral to and constitutive of the Enlightenment project of modernity in both its epistemic and institutional dimensions, a task for which historical and theoretical resources beyond Adorno and Foucault would be required. Fundamental questions about modernity, the human subject, and freedom also emerge from an encounter between critical theory in the Frankfurt School tradition and Caribbean thought (Sealey and Davis forthcoming). In a similar vein, contemporary critics of the persistence of colonial structures point to how a denial of the colonial past reaffirms a violent global color line (Mbembe 2016) that affects how societies treat Indigenous peoples (Coulthard 2014) and racialized and migrant populations (Celikates 2022).

4.2 Diagnosing Crises

Diagnosing crises, and the social contradictions that give rise to them, is a hallmark of Hegelian-Marxist critical theory. Marx famously diagnosed capitalism as a crisis-ridden social system, and the early work of the first generation of the Frankfurt School was a response to the economic, social, and political crises of their time. Dialectic of Enlightenment (Horkheimer and Adorno 1947) can be understood as addressing the crisis of reason that was experienced with the rise of National Socialism, but the critique of instrumental reason was disconnected from more concrete crises and struggles. Habermas aimed to restore the link between critique and crisis beginning with his 1973 book Legitimation Crisis (Benhabib 1986, 252–3, Cordero 2017, Ch. 3). Writing in the context of state-managed capitalism, Habermas diagnosed the distinctively political contradictions and potential for political crises within a social system that aims to steer the economy and manage economic crises (a point influentially elaborated by Offe 1984).

In subsequent decades, crisis critique, along with the critique of capitalism, was largely abandoned by Frankfurt School theorists (for a notable exception see Postone 1993). Renewed theoretical interest has coincided with rising public concern about social, political, and economic systems currently in, or always seemingly on the brink of, crisis, all against the backdrop of the unfolding effects of the ongoing climate catastrophe.

Nancy Fraser was one of the first critical theorists to revive crisis critique and to do so as part of a comprehensive critique of capitalism that renews the link between analytical diagnosis and critique (Fraser 2011, 2014; see Wellmer 2014 for a critique of the Frankfurt School’s earlier neglect). What distinguishes Fraser’s approach is that it posits capitalism as the unifying causal link among seemingly distinct crises – in relation to care work, the environment, and political institutions – by viewing capitalism as an institutionalized social order in which the economic system “cannibalizes” the very conditions that make it possible within the spheres of social reproduction, the natural environment, and the political system (Fraser 2022). Fraser combines analysis of “objective” social conditions – contradictions and crises – with an orientation toward social movements by analyzing the “boundary struggles” that arise at the seams between the economic system and other domains, making the case for these struggles to unite around an anti-capitalist agenda.

In a similar way, Rahel Jaeggi has developed a crisis-oriented theory of immanent critique (2014, Ch. 6) that is not limited to diagnosing systemic dysfunction but includes the normative expectations and self-understandings of social agents (Jaeggi 2017a; see Fraser and Jaeggi 2018), but at a more abstract theoretical level than Fraser’s immanent analysis of capitalism as a social order. Like Fraser and Jaeggi, Albena Azmanova argues for renewed attention to the critique of capitalism but is skeptical about how helpful “crisis” talk is (2014) and maintains that radical social change is possible without crisis, revolution, or utopia through a united struggle against forms of precarity that are endemic to contemporary capitalism (2020). More generally, the turn to economic crisis dynamics has also led to a renewed interest in work – its general significance, pathologies, and emancipatory potential (Jaeggi 2017b, Dejours et al. 2018, Honneth 2023).

Turning specifically to the ecological crisis, Frankfurt School theorists have only recently begun taking seriously the task of rethinking their approach to critical theory in the current context of an ongoing ecological disaster on a global scale (for an early exception, see Vogel 1996). Some critical theorists argue that this situation calls for a new paradigm of “Critical Naturalism” (Gregoratto et al., 2022); others argue for a fundamental rethinking of Western conceptions of human freedom and a radical shift in conceptions of the ethically good life as a precondition for the kind of radical social change required by the current crisis (Cooke 2020, 2023). Fraser focuses on the role of capitalism in the climate catastrophe and the need for eco-politics to be anti-capitalist so that we can reassert control over, and begin to reinvent from the ground up, our relation to nature (Fraser 2021, 2022; see Bernstein 2022 for a recent approach to such rethinking).

In rethinking our conception of nature, given the lack of serious attention to theorizing about nature in the second and, until quite recently, third generation of the Frankfurt School, it is not surprising that many critical theorists have looked more to the first generation (see the collected essays in Biro 2011), with Adorno’s work viewed as a promising starting point for rethinking humans’ relation to nature (Cook 2011, Cassegård 2021, Ch. 3). Cook argues that the “project of showing that human history is always also natural history and that non-human nature is entwined with history… informs all Adorno’s work” and that there are important affinities between his work and proponents of radical ecology (Cook 2011, 1, 5–6). On the other hand, the view of nature as having a kind of otherness that is beyond and not fully graspable by humans – a view expressed at times by Adorno and Horkeimer as well as Marcuse – has been criticized in favor of a more Hegelian-Marxist approach that sees “nature” as a product of human activity (Vogel 1996, 2011). Others argue for reviving critical engagement with Marcuse’s work as a resource for addressing the ecological crisis, with its combination of a critique of science and technology (most radically, as a call for a “new science”) with the idea that social transformation must include a changed, aesthetic relation to nature (Feenberg 2023a, 2023b). At this point, it is clear that there must be more engagement between Frankfurt School theorists and the many “critical ecologies” being developed today, e.g., deep ecology, eco-feminism, eco-socialism, ecological Marxism, environmental justice, indigenous and decolonial ecologies, and new materialism (on the recent dialogue between Frankfurt School theorists and new materialism, see Rosa et al., 2021).

Finally, Frankfurt School theorists have turned their attention to political crises and the rise of right-wing populist, authoritarian, and neo-fascist movements, parties, and governments (Brown, Gordon, and Pensky 2018, Gordon 2017, Abromeit 2016). This crisis is particularly important because adequately addressing the economic and ecological crises of our time requires political solutions, which will be hindered by political systems that are themselves in crisis, thereby contributing to a regressive dynamic (Jaeggi 2022, Forst 2023).

From the perspective of critical theorists, there seem to be two aspects of the political crisis that are often missing from mainstream liberal accounts. The first pertains to the genesis and the causes of the crisis (Brown 2019, Gambetti 2020). Against accounts that see authoritarianism only in terms of a rupture with and as entirely foreign to liberal democracy, they argue that we need to examine the continuities and enabling conditions that allow authoritarian tendencies to arise from within liberal-democratic capitalist societies. Without analyzing the neoliberal restructuring of social relations and the ways in which populist and authoritarian movements exploit electoral strategies, fragmented public spheres, and liberal ideological frameworks such as “freedom of speech,” the critique of and resistance to them will necessarily remain truncated.

The second aspect pertains to the dynamic of authoritarianism and the political crisis it engenders. Beyond focusing on its political dimension (e.g. political aims and values), critical theorists have sought to analyze the socio-cultural, affective, and psycho-social dynamics of authoritarianism and its attractiveness to populations that seem to have little to gain from the election of populist leaders (Marasco 2018, Brown 2019, McAfee 2019, Redecker 2020, Zaretsky 2022). These approaches can draw on and are supported by Adorno’s analysis (1967a) of core features of authoritarian right-wing populism. First, it is not so much actual abandonment but a feared, anticipated, or imagined abandonment, along with a perceived loss of privileges that had come to seem natural, that are the driving force of the rise of a reactionary authoritarianism that then gets misdescribed as a revolt of the oppressed and exploited. Second, the proponents of authoritarianism, following an antisemitic and/or racist logic, personalize the blame for their fears and feelings of abandonment by projecting it onto groups they classify as alien, rather than attributing it to structural features of society.

In responding to all the crises discussed here – economic, ecological, and political – critical theorists must grapple with a number of challenges. Purely at the level of theory, there is the question of whether positing unity or convergence among crises is diagnostically accurate. At a practical level, it remains to be seen whether a unity thesis will be politically motivating and whether a convergence of social struggles is indeed on the horizon. The issue of practice also bears on the question of whether and to what extent the objective conditions of crisis and contradiction diagnosed by critical theorists actually affect people’s everyday lived experience and become motivating factors for political movements (see Section 2.5 ). Such questions about the relation between theory and practice have long been a focus of critical theorists and have recently gained attention in theorizing about a range of critical and political practices.

While overcoming the gap between theory and practice has been a central methodological and political concern for critical theorists, critics have pointed out the prominent turn away from practice to theory in the first generation – accused by Lukács of taking up residence in the “Grand Hotel Abyss” (Lukács 1963, 22) – and the continued marginalization of critical praxis in later generations (Harcourt 2020). There are multiple grounds for challenging this assessment. Frankfurt School theorists had arguments all along about how to assess and relate to radical movements, such as the student movement of 1968 (Adorno and Marcuse 1969, Freyenhagen 2014, Pickford 2023), and there has always been a strand that continuously engaged with struggles and movements, from Marcuse to Negt and Kluge and Fraser. Some critical theorists have focused on deliberative democracy, the public sphere, and civil society (Habermas 1962, 1992, 2021, Cohen and Arato 1992, Benhabib 2004, Lafont 2019) as core fora for critical practice, while others have argued for critical theory itself to be democratized and understood as a critical practice (Bohman 2003, Celikates 2009).

Still, many of these approaches have been criticized for prioritizing institutional achievements over struggles and critical practices, and reform over revolution. Given the challenges outlined above (4.2), it is not surprising that some recent work tries to reverse this tendency by exploring more radical responses to such crises. These attempts notably push beyond the dichotomy between reform and revolution – for example, by promoting non-reformist reforms that could “alter the terrain on which future struggles will be waged, thus expanding the set of feasible options for future reforms” (Fraser, in Fraser and Honneth 2003, 79) – and mine the rich history and present of radical struggles outside traditional forms of political organizing such as the party or reimagine the party in radical ways (Dean 2016).

The range of critical practices engaged with by critical theorists past and present is extensive (for an inventory, see Harcourt 2020, Ch. 15). Frankfurt School theorists of earlier generations covered various forms of resistance, from the “Great Refusal” of the 1960s (Marcuse) and the potential for resistance in independent thinking and critical analysis in the face of universal reification (Adorno) to civil disobedience as a sign of a dynamic public sphere and civil society (Habermas 1983b, Cohen and Arato 1992, Ch. 11). More recently, critical theorists within various traditions have analyzed forms of disobedience (direct, digital, migrant etc.) as political practices of contestation and struggles for democratization “from below” (Young 2001, Smith 2013, Scheuerman 2018, Celikates 2019b). Other practices of resistance that do not directly engage with state institutions or appeal to the broader public include forms of sabotage (Malm 2020), fleeing, withdrawal, or defection. These turn away from what are seen as state-oriented struggles for visibility, recognition, or representation (Virno 2004, Roberts 2015) and towards subaltern forms of sociality (Moten and Harney 2013) and counter-communities that prefigure fundamental alternatives for living together (Loick 2021). Emphasizing the revolutionary dimension of critical practices, theorists have drawn on the abolitionist tradition of struggles against slavery and colonialism, and its revitalization in movements like Black Lives Matter, to call for a fundamental critique of racial capitalism and its entanglement with the punitive state, and a correspondingly radical transformation of all social relations and institutions (Davis 2005, Gilmore 2022). Critical theorists have also explored political practices of assembling (Butler 2015), occupying, striking, and reorganizing processes of social reproduction (Gago 2019), linking these to the need to rethink revolution beyond the model of a single break or event and more as an interstitial process (Redecker 2018, Saar 2020).

Whether the new revolutionary subjects and struggles that emerge in these critical practices will indeed converge to fundamentally challenge the existing order, open up new pathways to emancipation, and develop emancipated – more just, democratic, and sustainable – modes of living together remains to be seen. Horkheimer’s quip still holds: “if the proof of the pudding is in the eating, the eating here is still in the future” (1937a [1972, 220–1]). Against this background, theoretical explorations of critical practices – in the multiplicity of their forms, terrains, and actors – can be seen as part of the ongoing attempt to bring theory and practice together with an emancipatory orientation in light of the crises and struggles of the age. This approach has characterized the Frankfurt School from its very beginnings and has been a driving force in its continual (self-)transformation, making it into one of the most influential paradigms in social philosophy today.

  • Abromeit, John, 2016, “Critical Theory and the Persistence of Right-Wing Populism”, Logos: A Journal of Modern Society and Culture , 15(2) [ Abromeit 2016 available online ].
  • Adorno, Theodor W., 1931 [year this lecture was given], “Die Aktualität der Philosophie”, in Theodor W. Adorno, Gesammelte Schriften I: Philosophische Frühschriften , Rolf Tiedemann (ed.), Frankfurt am Main: Suhrkamp, 1973, pp. 325–344; translated as “The Actuality of Philosophy”, Benjamin Snow (trans.), Telos , 31 (1977): 120–133.
  • –––, 1936 “Wiesengrund-Adorno an Benjamin, 18. März 1936”, in Theodor W. Adorno and Walter Benjamin, Briefwechsel 1928–1940 , Henri Lonitz (ed.), Frankfurt am Main, 1994, pp. 168–177; translated as March 18, 1936, “Wiesengrund-Adorno to Benjamin, March 18, 1936”, Theodor W. Adorno and Walter Benjamin , The Complete Correspondence 1928–1940 ,, Nicholas Walker (trans.), Henri Lonitz (ed.), Cambridge: Polity Press, 1999, pp. 127–133.
  • –––, 1938, “Über den Fetischcharakter in der Musik und die Regression des Hörens”, Zeitschrift für Sozialforschung , 7(3), 321–356; translated as “On the Fetish Character in Music and the Regression of Listening”, Susan L. Gillespie (trans.), in Theodor W. Adorno, Essays on Music , Richard Leppert (ed.), Berkeley: University of California Press, 2002, pp. 288–317.
  • –––, 1951a, “Kulturkritik und Gesellschaft”, in Karl Gustav Specht (ed.), Soziologische Forschung unserer Zeit , Köln and Opladen: Westdeutscher Verlag, 1951, pp. 228–240, republished in Theodor W. Adorno, Prismen: Kulturkritik und Gesellschaft , Frankfurt am Main: Suhrkamp, 1955, pp. 7–31; translated as “Cultural Criticism and Society”, in Theodor W. Adorno, Prisms , Samuel Weber and Shierry Weber (trans.), Cambridge, MA: MIT Press, 1981, pp. 17–34.
  • –––, 1951b, “Freudian Theory and the Pattern of Fascist Propaganda”, in Géza Roheim (ed.), Psychoanalysis and the Social Sciences Vol. 3 , New York: International Universities Press, 279–300. Reprinted in The Culture Industry: Selected Essays on Mass Culture , Jay Bernstein (ed.), New York: Routledge, 1991, pp. 132–157.
  • –––, 1951c, Minima Moralia: Reflexionen aus dem beschädigten Leben , Frankfurt am Main: Suhrkamp; translated as Minima Moralia: Reflections from Damaged Life , Edmund Jephcott (trans.), London: Verso, 2005.
  • –––, 1955, “Schuld und Abwehr”, in Friedrich Pollock (ed.), Gruppenexperiment: Ein Studienbericht , Frankfurt am Main: Europäische Verlagsanstalt, 278–428; translated as Guilt and Defense: On the Legacies of National Socialism in Postwar Germany , Jeffrey K. Olick and Andrew J. Perrin (eds./trans.), Cambridge, MA: Harvard University Press, 2010.
  • –––, 1957, “Soziologie und empirische Forschung”, in K . Ziegler (ed.), Wesen und Wirklichkeit des Menschen: Festschrift für Helmuth Plessner , Göttingen: Vandenhoeck & Ruprecht, pp. 245–260; translated as “Sociology and Empirical Research”, Glyn Adey and David Frisby (trans.), in Theodor W. Adorno et al. (eds.), The Positivist Dispute in German Sociology , London: Heinemann, 1976, pp. 68–86.
  • –––, 1963a [year this transcribed lecture course was given], Probleme der Moralphilosophie , Frankfurt am Main: Suhrkamp, 1996; translated as Problems of Moral Philosophy , Rodney Livingstone (trans.), Stanford, CA: Stanford University Press, 2000.
  • –––, 1963b, Drei Studien zu Hegel , Frankfurt am Main: Suhrkamp; translated as Hegel: Three Studies , Shierry Weber Nicholsen (trans.), Cambridge, MA: MIT Press, 1993.
  • –––, 1966a, Negative Dialektik , Frankfurt am Main: Suhrkamp; translated as Negative Dialectics , E. B. Ashton (trans.), New York: Seabury Press, 1973.
  • –––, 1966b, “Gesellschaft”, in Hermann Kunst and Siegfried Grundmann (eds.), Evangelisches Staatslexikon , Stuttgart: Kreuz Verlag, pp. 636–643; translated as “Society”, Fredric R. Jameson (trans.), Salmagundi , 10–11 (1969): 144–153.
  • –––, 1969a, “Zur Spezifikation der kritischen Theorie”, in Theodor W. Adorno Archiv (ed.), Adorno. Eine Bildmonographie , Frankfurt am Main: Suhrkamp, p. 292.
  • –––, 1969b, “Marginalien zu Theorie und Praxis”, Die Zeit , No. 33 (1969); translated as “Marginalia to Theory and Praxis”, Henry W. Pickford (trans.), in Critical Models: Interventions and Catchwords , New York: Columbia University Press, 2005, pp. 259–278.
  • –––, 1967a [year this transcribed lecture was given], Aspekte des neuen Rechtsradikalismus , Berlin: Suhrkamp, 1999; translated as Aspects of the New Right-Wing Extremism , Wieland Hoban (trans.), Cambridge: Polity, 2020.
  • –––, 1967b, “Résumé über Kulturindustrie”, in Theodor W. Adorno, Ohne Leitbild: Parva Aesthetica , Frankfurt am Main: Suhrkamp, pp. 60–70; translated as “The Culture Industry Reconsidered”, Anson G. Rabinbach (trans.), in Jay Bernstein, (ed.), The Culture Industry: Selected Essays on Mass Culture , New York: Routledge, 1991, pp. 98–106.
  • –––, 1970, Ästhetische Theorie , Frankfurt am Main: Suhrkamp; translated as Aesthetic Theory , Robert Hullot-Kentor (trans.), Minneapolis: University of Minnesota Press, 1977.
  • Adorno, Theodor W., Else Frenkel-Brunswik, Daniel Levinson, and Nevitt Sanford, 1950, The Authoritarian Personality , with a new Introduction by Peter E. Gordon, New York: Verso, 2019.
  • Adorno, Theodor W., Hans Albert, Ralf Dahrendorf, Jürgen Habermas, Harald Pilot, and Karl R. Popper, 1969, Der Positivismusstreit in der deutschen Soziologie , Neuwied/Berlin: Luchterhand; translated as The Positivist Dispute in German Sociology , Glyn Adey and David Frisby (trans.), London: Heinemann, 1976.
  • Adorno, Theodor W. and Herbert Marcuse, 1969, “Correspondence on the German Student Movement”, New Left Review , 233 (1999), 123–136.
  • Agamben, Giorgio, 1995, Homo Sacer: Il potere sovrano e la nuda vita , Turin: Einaudi; translated as Homo Sacer: Sovereign Power and Bare Life , Daniel Heller-Roazen (trans.), Stanford: Stanford University Press, 1998.
  • Allen, Amy, 2008, The Politics of Our Selves: Power, Autonomy, and Gender in Contemporary Critical Theory , New York: Columbia University Press.
  • –––, 2010, “Third Generation Critical Theory: Benhabib, Fraser, and Honneth”, in Rosi Braidotti (ed.), After Poststructuralism: Transitions and Transformations , Durham: Acumen, pp. 129–48.
  • –––, 2012, “The Public Sphere: Ideology and/or Ideal?”, Political Theory , 40(6): 822–829. doi:10.1177/0090591712457664
  • –––, 2014, “Reason, Power and History: Re-reading the Dialectic of Enlightenment ”, Thesis Eleven , 120(1): 10–25. doi:10.1177/0725513613519588
  • –––, 2015, “Emancipation without Utopia: Subjection, Modernity, and the Normative Claims of Feminist Critical Theory”, Hypatia , 30(3): 513–29. doi:10.1111/hypa.12160
  • –––, 2016, The End of Progress: Decolonizing the Normative Foundations of Critical Theory , New York: Columbia University Press.
  • –––, 2019, “Critical Theory and Feminism”, in Gordon, Peter, Espen Hammer, and Axel Honneth (eds.), The Routledge Companion to the Frankfurt School , London: Routledge, pp. 528–541.
  • –––, 2021, Critique on the Couch: Why Critical Theory Needs Psychoanalysis , New York: Columbia University Press.
  • Allen, Amy, and Eduardo Mendieta, (eds.), 2021, Decolonizing Ethics: The Critical Theory of Enrique Dussel , University Park, PA: Pennsylvania State University Press.
  • Allen, Amy, and Brian O’Connor (eds.), 2019, Transitional Subjects: Critical Theory and Object Relations , New York: Columbia University Press.
  • Anderson, Joel, 2000, “The ‘Third Generation’ of the Frankfurt School”, Intellectual History Newsletter 22, 49–61.
  • Apel, Karl-Otto, 1985, “Ist die Ethik der idealen Kommunikationsgemeinschaft eine Utopie? Zum Verhältnis von Ethik, Utopie und Utopiekritik”, in Wilhelm Vosskamp (ed.), Utopieforschung , Frankfurt: Suhrkamp; translated as “Is the Ideal Communication Community a Utopia? On the Relationship between Ethics, Utopia, and the Critique of Utopia”, David Frisby (trans.), in Seyla Benhabib and Fred Dallmayr (eds.), The Communicative Ethics Controversy , Cambridge, MA: MIT Press, 1990, pp. 23–59.
  • –––, 1989, “Normative Begründung der ‘Kritischen Theorie’” durch Rekurs auf lebensweltliche Sittlichkeit? Ein transzendentalpragmatisch orientierter Versuch, mit Habermas gegen Habermas zu denken”, in Axel Honneth, Thomas McCarthy, Claus Offe, and Albrecht Wellmer (eds.), Zwischenbetrachtungen im Prozess der Aufklärung: Jürgen Habermas zum 60. Geburtstag , Frankfurt am Main: Suhrkamp, 15–65; translated as “Normatively Grounding ‘Critical Theory’ through Recourse to Lifeworld? A Transcendental-Pragmatic Attempt to Think With Habermas Against Habermas”, William Rehg (trans.), in Axel Honneth, Thomas McCarthy, Claus Offe, and Albrecht Wellmer (eds.), Philosophical Interventions Into the Unfinished Project of Enlightenment , Cambridge, MA: MIT Press, 1992, pp. 125–70.
  • Azmanova, Albena, 2014, “Crisis? Capitalism is Doing Very Well. How is Critical Theory?”, Constellations , 21(3): 351–365. doi:10.1215/00382876-7165857
  • –––, 2020, Capitalism on Edge: How Fighting Precarity Can Achieve Radical Change Without Crisis or Utopia , New York: Columbia University Press.
  • Balibar, Etienne, and Immanuel Wallerstein, 1988, Race, nation, classe: les identités ambiguës , Paris: La Découverte; translated as Race, Nation, Class. Ambiguous Identities , Chris Turner (trans.), New York: Verso, 1991.
  • Bardawil, Fadi, 2018, “Césaire with Adorno: Critical Theory and the Colonial Problem”, South Atlantic Quarterly , 117(4): 773–789. doi:10.1215/00382876-7165857
  • Baum, Bruce, 2015, “Decolonizing Critical Theory”, Constellations , 22(3): 420–434. doi:10.1111/1467-8675.12169
  • Baynes, Kenneth, 2016, Habermas , New York: Routledge.
  • Benhabib, Seyla, 1986, Critique, Norm, and Utopia: A Study of the Foundations of Critical Theory , New York: Columbia University Press.
  • –––, 1992, Situating the Self: Gender, Community and Postmodernism in Contemporary Ethics , New York: Routledge.
  • –––, 2004, The Rights of Others: Aliens, Residents, and Citizens , Cambridge: Cambridge University Press.
  • Benhabib, Seyla, Judith Butler, Drucilla Cornell, and Nancy Fraser, 1995, Feminist Contentions: A Philosophical Exchange , New York: Routledge.
  • Benjamin, Walter, 1920/21, “Zur Kritik der Gewalt”, in Archiv für Sozialwissenschaft und Sozialpolitik , 47(3): 809–832; translated as “Toward the Critique of Violence”, Julia Ng (trans.), in Peter Fenves and Julia Ng (eds.), Toward the Critique of Violence: A Critical Edition , Stanford University Press, 2021, pp. 39–60.
  • –––, 1936, “Das Kunstwerk im Zeitalter seiner technischen Reproduzierbarkeit”, originally published as “L’œuvre d’art à l’époque de sa réproduction mécanisée”, Pierre Klossowski (trans.), Zeitschrift für Sozialforschung , 5(1), 40–68, all textual variants can be found in Walter Benjamin, Das Kunstwerk im Zeitalter seiner technischen Reproduzierbarkeit (Walter Benjamin Werke und Nachlaß: Kritische Gesamtausgabe vol. 16), Burkhardt Lindner (ed.), Berlin: Suhrkamp, 2012, the essay was translated as “The Work of Art in the Age of its Technological Reproducibility”, Michael W. Jennings (trans.), Grey Room , 39 (2010): 11–37. doi:10.1162/grey.2010.1.39.11
  • –––, 1940, “Über den Begriff der Geschichte”, in Walter Benjamin, Gesammelte Schriften I , Rolf Tiedemann and Hermann Schweppenhäuser (eds.), Frankfurt am Main, 1974, pp. 691–706; translated as “On the Concept of History”, Harry Zohn (trans.) in Howard Eiland and Michael W. Jennings (eds.) Walter Benjamin: Selected Writings (Volume 4), Cambridge, MA: Harvard University Press, 2006, pp. 389–400.
  • –––, 1955, Schriften , 2 vols., Theodor W. Adorno and Gretel Adorno (eds.), Frankfurt am Main: Suhrkamp; translated in parts as Illuminations , Harry Zohn (trans.), Hannah Arendt (ed.), New York: Harcourt, Brace & World, 1968.
  • Bernstein, Jay, 2001, Adorno: Disenchantment and Ethics , Cambridge: Cambridge University Press.
  • Bernstein, Richard, 2010, The Pragmatic Turn , Malden, MA: Polity.
  • –––, 2022, The Vicissitudes of Nature: From Spinoza to Freud , Malden, MA: Polity.
  • Bhambra, Gurminder K., 2021, “Decolonizing Critical Theory?: Epistemological Justice, Progress, Reparations”, Critical Times , 4(1): 73–89. doi:10.1215/26410478-8855227
  • Bhambra, Gurminder K., and John Holmwood, 2021, Colonialism and Modern Social Theory , Malden, MA: Polity.
  • Biro, Andrew, 2011, Critical Ecologies: The Frankfurt School and Contemporary Environmental Crises , Toronto: University of Toronto Press.
  • Bohman, James, 2003, “Critical Theory as Practical Knowledge: Participants, Observers, and Critics”, in S. P. Turner and P. A. Roth (eds.), The Blackwell Guide to the Philosophy of the Social Sciences , Oxford: Blackwell, pp. 91–109.
  • –––, 2007, Democracy Across Borders: From Dêmos to Dêmoi, Cambridge, MA: MIT Press.
  • Bojadžijev, Manuela, 2020, “Anti-Racism as Method”, in John Solomos (ed.), The Routledge International Handbook of Contemporary Racisms , London: Routledge 2020, pp. 193–204.
  • Bourdieu, Pierre, 1980, Le sens pratique , Paris: Minuit; translated as The Logic of Practic e, Richard Nice (trans.), Stanford: Stanford University Press, 1992.
  • Brown, Wendy (ed.), 2006, “Feminist Theory and the Frankfurt School”: a Special Issue of differences: A Journal of Feminist Cultural Studies , 17(1).
  • –––, 2019, In the Ruins of Neoliberalism: The Rise of Antidemocratic Politics in the West , New York: Columbia University Press.
  • –––, 2022, “Rethinking Politics and Freedom in the Anthropocene”, Crisis and Critique , 9(2): 24–44 [ Brown 2022 available online ].
  • Brown, Wendy, and Rainer Forst, 2014, The Power of Tolerance: A Debate , New York: Columbia University Press.
  • Brown, Wendy, Peter Gordon, and Max Pensky, 2018, Authoritarianism. Three Inquiries in Critical Theory , Chicago: The University of Chicago Press.
  • Brunkhorst, Hauke, 1983, “Paradigmenkern und Theoriedynamik der Kritischen Theorie der Gesellschaft”, Soziale Welt , 34: 22–36; translated as “Paradigm-core and theory-dynamics in critical social theory: people and programs”, Peter Krockenberger (trans.), Philosophy & Social Criticism , 24(6) (1998): 67–110.
  • –––, 2002, Solidarität: Von der Bürgerfreundschaft zur globalen Rechtsgenossenschaft , Frankfurt am Main: Suhrkamp; translated as Solidarity: From Civic Friendship to a Global Legal Community , Jeffrey Flynn (trans.), Cambridge, MA: MIT Press, 2005.
  • –––, 2014, Critical Theory of Legal Revolutions: Evolutionary Perspectives , New York: Bloomsbury.
  • Buchstein, Hubertus, 2020, “Otto Kirchheimer and the Frankfurt School: Failed Collaborations in the Search for a Critical Theory of Politics”, New German Critique , 47(2): 81–106.
  • Buck-Morss, Susan, 1977, The Origin of Negative Dialectics: Theodor W. Adorno, Walter Benjamin and the Frankfurt Institute , New York: The Free Press.
  • –––, 1989, The Dialectics of Seeing: Walter Benjamin and the Arcades Project , Cambridge, MA: MIT Press.
  • –––, 1992, “Aesthetics and Anaesthetics: Walter Benjamin’s Artwork Essay Reconsidered”, October , 62: 3–41. doi:10.2307/778700
  • –––, 2009, Hegel, Haiti, and Universal History , Pittsburgh: University of Pittsburgh Press.
  • Butler, Judith, 1990, Gender Trouble , London: Routledge.
  • –––, 1997, The Psychic Life of Power: Theories in Subjection , Stanford, CA: Stanford University Press.
  • –––, 2012, Parting Ways: Jewishness and the Critique of Zionism , New York: Columbia University Press.
  • –––, 2015, Notes Toward a Performative Theory of Assembly , Cambridge, MA: Harvard University Press.
  • Butler, Judith, Jürgen Habermas, Charles Taylor, and Cornel West, 2011, The Power of Religion in the Public Sphere , New York: Columbia University Press.
  • Cassegård, Carl, 2021, Toward a Critical Theory of Nature: Capital, Ecology, and Dialectics , New York: Bloomsbury.
  • Catlin, Jonathon, 2023, “Antisemitism and Racism ‘After Auschwitz’: Adorno on the ‘Hellish Unity’ of ‘Permanent Catastrophe’ ”, in Marcel Stoetzler (ed.), Critical Theory and the Critique of Antisemitism , New York: Bloomsbury, pp. 203–230.
  • Celikates, Robin, 2006, “From Critical Social Theory to a Social Theory of Critique: On the Critique of Ideology after the Pragmatic Turn”, Constellations , 13(1): 21–40. doi:10.1111/j.1351-0487.2006.00438.x
  • –––, 2009, Kritik als soziale Praxis: Gesellschaftliche Selbstverständigung und kritische Theorie , Frankfurt am Main: Campus; translated as Critique as Social Practice: Critical Theory and Social Self-Understanding , Naomi van Steenbergen (trans.), London: Rowman & Littlefield, 2018.
  • –––, 2019a, “Critical Theory and the Unfinished Project of Mediating Theory and Practice”, in Peter Gordon, Espen Hammer, and Axel Honneth (eds.), The Routledge Companion to the Frankfurt School , London: Routledge, pp. 206–220.
  • –––, 2019b, “Constituent Power Beyond Exceptionalism: Irregular Migration, Disobedience, and (Re-)Constitution”, Journal of International Political Theory , 15(1): 67–81. doi:10.1177/1755088218808311
  • –––, 2022, “Remaking the Demos ‘from Below’? Critical Theory, Migrant Struggles, and Epistemic Resistance”, in Didier Fassin and Axel Honneth (eds.), Crisis Under Critique: How People Assess, Transform, and Respond to Critical Situations , New York: Columbia University Press, pp. 97–120.
  • Celikates, Robin, Sally Haslanger, and Jason Stanley (eds.), forthcoming, Analyzing Ideology , Oxford: Oxford University Press.
  • Celikates, Robin, Axel Honneth, and Rahel Jaeggi, 2023, “The Working Sovereign: A conversation with Axel Honneth”, Journal of Classical Sociology , 23(3): 318–338. doi:10.1177/1468795X231170980
  • Chambers, Simone, 2022, “Can Postmetaphysical Reason Escape its Provincial Roots?”, in Tom Bailey (ed.), Deprovincializing Habermas: Global Perspectives , Second Edition , New York: Routledge, pp. 229–248.
  • Chari, Anita, 2015, A Political Economy of the Senses: Neoliberalism, Reification, Critique , New York: Columbia University Press.
  • Cohen, Jean L., and Andrew Arato, 1992, Civil Society and Political Theory , Cambridge, MA: MIT Press.
  • Collins, Patricia Hill, 1990, Black Feminist Thought: Knowledge, Consciousness, and the Politics of Empowerment , London: Routledge. Second edition published in 2000.
  • –––, 2019, Intersectionality as Critical Social Theory , Durham and London: Duke University Press. doi:10.1515/9781478007098
  • Cook, Deborah, 2004, Adorno, Habermas, and the Search for a Rational Society , London and New York: Routledge.
  • –––, 2011, Adorno on Nature , Durham: Acumen.
  • Cooke, Maeve, 2006, Re-Presenting the Good Society , Cambridge, MA: MIT Press.
  • –––, 2020, “Ethics and Politics in the Anthropocene”, Philosophy & Social Criticism , 46(10): 1167–1181. doi:10.1177/0191453720903491
  • –––, 2023, “Reenvisioning Freedom: Human Agency in Times of Ecological Disaster”, Constellations , 30: 119–127. doi:10.1111/1467-8675.12681
  • Cordero, Rodrigo, 2017, Crisis and Critique: On the Fragile Foundations of Social Life , New York: Routledge.
  • Coulthard, Glen Sean, 2014, Red Skin, White Masks: Rejecting the Colonial Politics of Recognition , Minneapolis: University of Minnesota Press.
  • Crenshaw, Kimberlé, Neil Gotanda, Gary Peller, and Kendall Thomas, 1995, “Introduction”, Critical Race Theory: The Key Writings that Formed the Movement , New York: The New Press, pp. viii–xxxii.
  • Davis, Angela Y., 1983, Women, Race and Class , New York: Vintage.
  • –––, 2004, “Marcuse’s Legacies”, in John Abromeit and W. Mark Cobb (eds.), Herbert Marcuse: A Critical Reader . New York, Routledge, pp. 43–50.
  • –––, 2005, Abolition Democracy , New York: Seven Stories Press.
  • Dean, Jodi, 2016, Crowds and Party , London: Verso.
  • Dejours, Christophe, Jean-Philippe Deranty, Emmanuel Renault, and Nicholas H. Smith, 2018, The Return of Work in Critical Theory: Self, Society, Politics , New York: Columbia University Press.
  • Demirović, Alex, 2016, “The Frankfurt School, Critical Theory, and Sociology at the Institute for Social Research (1950 to 1960)”, in Gabriel R. Ricci (ed.), The Persistence of Critical Theory , London: Routledge, pp. 25–40.
  • Deranty, Jean-Philippe, 2021, “Negativity in Recognition: Post-Freudian Legacies in Contemporary Critical Theory”, in Ikäheimo, Heikki, Kristina Lepold and Titus Stahl (eds.), Recognition and Ambivalence , New York: Columbia University Press, pp. 223–255.
  • Derrida, Jacques, 1990 [year the lecture was given], Force de loi , Paris: Galilée, 1994; translated as “The Force of Law”, Mary Quaintance (trans.), in Drucilla Cornell, Michel Rosenfeld, and David G. Carlson (eds.), Deconstruction and the Possibility of Justice , New York: Routledge, 1992, pp. 3–67.
  • Dews, Peter, 1987, Logics of Disintegration: Poststructuralist Thought and the Claims of Critical Theory , London: Verso.
  • Dubiel, Helmut, 1978, Wissenschaftsorganisation und politische Erfahrung: Studien zur frühen Kritischen Theorie , Frankfurt am Main: Suhrkamp; translated as Theory and Politics: Studies in the Development of Critical Theory , Benjamin Gregg (trans.), Cambridge, MA: MIT Press, 1985.
  • Du Bois, W. E. B., 1935, Black Reconstruction in America, 1860–1880 , New York: The Free Press, 1998.
  • Dussel, Enrique, 1998, Ética de la Liberación en la edad de globalización y de la exclusión ; translated as Ethics of Liberation in the Age of Globalization and Exclusion , Eduardo Mendieta, Camilo Pérez Bustillo, Yolanda Angulo, and Nelson Maldonado-Torres (trans.), Durham, NC: Duke University Press, 2013.
  • –––, 2011, “From Critical Theory to the Philosophy of Liberation: Some Themes for Dialogue”, Transmodernity , 1(2): 16–43. doi.org:10.5070/T412011806
  • Eagleton, Terry, 1991, Ideology: An Introduction , London, Verso.
  • Feenberg, Andrew, 2023a, “Marcuse’s Critique of Technology Today”, Philosophy & Social Criticism 49(6): 672–685. doi:10.1177/01914537231164657
  • –––, 2023b, The Ruthless Critique of Everything Existing: Nature and Revolution in Marcuse’s Philosophy of Praxis , London: Verso.
  • Ferrara, Alessandro, 2008, The Force of the Example: Explorations in the Paradigm of Judgment , New York: Columbia University Press.
  • Ferrarese, Estelle, 2018, La fragilité du souci des autres: Adorno et le care , Lyon: ENS Éditions; translated as The Fragility of Concern for Others: Adorno and the Ethics of Care , Steven Corcoran (trans.), Edinburgh: Edinburgh University Press, 2020.
  • Finlayson, James Gordon, 2007, “Political, Moral and Critical Theory: On the Practical Philosophy of the Frankfurt School”, in Michael Rosen and B. Leiter (eds.), The Oxford Handbook of Continental Philosophy , Oxford: Oxford University Press, pp. 626–670.
  • –––, 2015, “The Artwork and the Promesse du Bonheur in Adorno”, European Journal of Philosophy , 23(3): 392–419. doi:10.1111/j.1468-0378.2012.00542.x
  • –––, 2019, The Habermas-Rawls Debate , New York: Columbia University Press.
  • Flynn, Jeffrey, 2014a, Reframing the Intercultural Dialogue on Human Rights: A Philosophical Approach , New York: Routledge.
  • –––, 2014b, “Truth, Objectivity, and Experience after the Pragmatic Turn: Bernstein on Habermas’s ‘Kantian Pragmatism’ ”, in Judith M. Green (ed.), Richard J Bernstein and the Pragmatist Turn in Contemporary Philosophy , Basingstoke and New York: Palgrave Macmillan, pp. 190–209.
  • –––, 2022, “Decentering Eurocentrism through Dialogue”, in Tom Bailey (ed.), Deprovincializing Habermas: Global Perspectives , Second Edition , New York: Routledge, pp. 249–270.
  • Fong, Benjamin Y., 2016, Death and Mastery: Psychoanalytic Drive Theory and the Subject of Late Capitalism , New York: Columbia University Press.
  • Forst, Rainer, 2007, Das Recht auf Rechtfertigung: Elemente einer konstruktivistischen Theorie der Gerechtigkeit , Berlin: Suhrkamp; translated as The Right to Justification: Elements of a Constructivist Theory of Justice , Jeffrey Flynn (trans.), New York: Columbia University Press, 2011.
  • –––, 2011, Kritik der Rechtfertigungsverhältnisse , Berlin: Suhrkamp; translated as Justification and Critique: Towards a Critical Theory of Politics , Ciaran Cronin (trans.), Cambridge: Polity, 2014.
  • –––, 2017, “Noumenal Alienation: Rousseau, Kant and Marx on the Dialectics of Self-Determination”, Kantian Review , 22(4): 523–551. doi:10.1017/S1369415417000267
  • –––, 2021a, Die noumenale Republik: Kritischer Konstruktivismus nach Kant , Berlin: Suhrkamp; translation, The Noumenal Republic: Critical Constructivism after Kant , Ciaran Cronin (trans.), forthcoming.
  • –––, (ed)., 2021b, “Symposium on Jürgen Habermas, Auch eine Geschichte der Philosophie ”, Constellations , 28(1): 1–147.
  • –––, 2023, “The rule of unreason: Analyzing (Anti-)Democratic Regression”, Constellations , 30(3): 217–224. doi:10.1111/1467-8675.12671
  • Foucault, Michel, 1973 [year this lecture was given], “La vérités et les formes juridiques”, Chimères , 10 (1990): 8–28; translated as “Truth and Juridical Forms”, in Michel Foucault, Power , ed. James D. Faubion, New York: New Press, 2000, pp. 31–45.
  • Fraser, Nancy, 1981, “Foucault on Modern Power: Empirical Insights and Normative Confusions”, PRAXIS International , 3: 272–287.
  • –––, 1985, “What’s Critical about Critical Theory? The Case of Habermas and Gender”, New German Critique , 35: 97–131. doi:10.2307/488202
  • –––, 1989, Unruly Practices: Power, Discourse, and Gender in Contemporary Social Theory , Minneapolis: University of Minnesota Press.
  • –––, 1990, “Rethinking the Public Sphere: A Contribution to the Critique of Actually Existing Democracy.” Social Text , 25/26: 56–80.
  • –––, 2011, “Marketization, Social Protection, Emancipation: Toward a Neo-Polanyian Conception of Capitalist Crisis”, in Craig Calhoun and Georgi Derlugian (eds.), Business as Usual: The Roots of the Global Financial Meltdown , New York University Press, pp. 137–58.
  • –––, 2013, Fortunes of Feminism: From State-Managed Capitalism to Neoliberal Crisis , London: Verso.
  • –––, 2014, “Behind Marx’s Hidden Abode”, New Left Review , 86: 55–72.
  • –––, 2016, “Contradictions of Capital and Care”, New Left Review , 100: 99–117.
  • –––, 2021, “Climates of Capital”, New Left Review , 127: 94–127.
  • –––, 2022, Cannibal Capitalism: How Our System is Devouring Democracy, Care, and the Planet – And What We Can Do about It , New York: Verso.
  • Fraser, Nancy, et al., 2014, Transnationalizing the Public Sphere , Kate Nash (ed.), Cambridge: Polity.
  • Fraser, Nancy, and Axel Honneth, 2003, Redistribution or Recognition? A Philosophical-Political Exchange , New York: Verso.
  • Fraser, Nancy and Rahel Jaeggi, 2018, Capitalism: A Conversation in Critical Theory , Brian Milstein (ed.), Cambridge: Polity.
  • Freyenhagen, Fabian, 2014, “Adorno’s Politics: Theory and Praxis in Germany’s 1960s”, Philosophy & Social Criticism , 40: 867–893. doi:10.1177/0191453714545198
  • –––, 2018, “Critical Theory: Self-Reflexive Theorizing and Struggles for Emancipation”, in: Oxford Research Encyclopedia of Politics [ Freyenhagen 2018 available online ].
  • Fricker, Miranda, 2007, Epistemic Injustice , Oxford: Oxford University Press.
  • Fromm, Erich, 1936, “Studien über Autorität und Familie. Sozialpsychologischer Teil”, in Max Horkheimer (ed.), Schriften des Instituts für Sozialforschung, Vol. V: Studien über Autorität und Familie , Paris: Librairie Félix Alcan; translated as “Studies on Authority and the Family. Socio-psychological Dimensions”, Fromm Forum , 24 (2020): 8–58.
  • –––, 1961, Marx’s Concept of Man , New York: Continuum.
  • Gago, Verónica, 2019, La potencia feminista: O el deseo de cambiarlo todo , Buenos Aires: Tinta Limón; translated as Feminist International: How to Change Everything , Liz Mason-Deese (trans.), London: Verso, 2020.
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  • Habermas, Jürgen, 1962, Strukturwandel der Öffentlichkeit: Untersuchungen zu einer Kategorie der bürgerlichen Gesellschaft , Neuwied, Berlin: Luchterhand; translated as The Structural Transformation of the Public Sphere: An Inquiry Into a Category of Bourgeois Society , Thomas Burger and Frederick Lawrence (trans.), Cambridge, MA: MIT Press, 1989.
  • –––, 1963, Theorie und Praxis: Sozialphilosophische Studien , Neuwied am Rhein and Berlin: Luchterhand. New and extended edition Frankfurt am Main: Suhrkamp, 1971; translated as Theory and Practice , John Viertel (trans.), Boston: Beacon Press, 1973.
  • –––, 1968a, Technik und Wissenschaft als ‘Ideologie’ , Frankfurt am Main: Suhrkamp; translated as Chapters 4–6 of Toward a Rational Society: Student Protest, Science, and Politics , Jeremy J. Shapiro (trans.), Boston: Beacon Press, 1970.
  • –––, 1968b, Erkenntnis und Interesse , Frankfurt am Main: Suhrkamp; translated as Knowledge and Human Interests , Jeremy J. Shapiro (trans.), Boston: Beacon Press, 1971.
  • –––, 1973a, “Nachwort”, in Jürgen Habermas, Erkenntnis und Interesse, Mit einem neuen Nachwort , Frankfurt am Main: Suhrkamp, pp. 367–417; translated as “A Postscript to Knowledge and Human Interests ”, Christian Lenhardt (trans.), Philosophy of the Social Sciences , 3: 157–189.
  • –––, 1973b, Legitimationsprobleme im Spätkapitalismus , Frankfurt am Main: Suhrkamp; translated as Legitimation Crisis , Thomas McCarthy (trans.), Boston: Beacon Press, 1975.
  • –––, 1981, Theorie des kommunikativen Handelns , 2 vols., Frankfurt am Main: Suhrkamp; translated as The Theory of Communicative Action , 2 vols., Thomas A. McCarthy (trans.), Boston: Beacon Press, 1984.
  • –––, 1983a, Moralbewusstsein und kommunikatives Handeln , Frankfurt am Main: Suhrkamp, translated as Moral Consciousness and Communicative Action , Christian Lenhardt and Shierry Weber Nicholsen (trans.), Cambridge, MA: MIT Press, 1990.
  • –––, 1983b, “Ziviler Ungehorsam: Testfall für den demokratischen Rechtsstaat”, in Peter Glotz (ed.), Ziviler Ungehorsam im Rechtsstaat , Frankfurt am Main: Suhrkamp, pp. 29–53; translated as “Civil Disobedience: Litmus Test for the Democratic Constitutional State”, Berkeley Journal of Sociology , 30: 95–116.
  • –––, 1985, Der philosophische Diskurs der Moderne: Zwölf Vorlesungen , Frankfurt am Main: Suhrkamp; translated as The Philosophical Discourse of Modernity: Twelve Lectures , Frederick Lawrence (trans.), Cambridge, MA: MIT Press, 1987.
  • –––, 1991, Erläuterungen zur Diskursethik , Frankfurt am Main: Suhrkamp; translated as Justification and Application: Remarks on Discourse Ethics , Ciaran Cronin (trans.), Cambridge, MA: MIT Press, 1993.
  • –––, 1992, Faktizität und Geltung: Beiträge zur Diskurstheorie des Rechts und des demokratischen Rechtsstaats , Frankfurt am Main: Suhrkamp; translated as Between Facts and Norms: Contributions to a Discourse Theory of Law and Democracy , William Rehg (trans.), Cambridge, MA: MIT Press, 1996.
  • –––, 1995a, “Reconciliation Through the Public Use of Reason: Remarks on John Rawls’s Political Liberalism”, The Journal of Philosophy , 92(3): 109–131. doi:10.5840/jphil199592335
  • –––, 1995b, “Kants Idee des ewigen Friedens aus dem historischen Abstand von 200 Jahren”, Kritische Jusitiz , 3: 293–319; translated as “Kant’s Idea of Perpetual Peace, with the Benefit of Two Hundred Years’ Hindsight”, in James Bohman and Matthias Lutz-Bachmann (eds.), Perpetual Peace: Essays on Kant’s Cosmopolitan Ideal , Cambridge, MA: MIT Press, 1997, pp. 113–153.
  • –––, 1996, “Vernünftig versus Wahr oder die Moral der Weltbilder”, in Die Einbeziehung des Anderen: Studien zur politischen Theorie , Frankfurt am Main: Suhrkamp; translated as “‘Reasonable’ versus ‘True,’ or the Morality of Worldviews”, Ciaran Cronin (trans.), in The Inclusion of the Other: Studies in Political Theory , Ciaran Cronin and Pablo De Greiff (eds.), Cambridge, MA: MIT Press, 1998, pp. 75-105.
  • –––, 1998, Die postnationale Konstellation: politische Essays , Frankfurt am Main: Suhrkamp; translated as The Postnational Constellation: Political Essays , Max Pensky (ed./trans.), Cambridge, MA: MIT Press, 2001.
  • –––, 1999, Wahrheit und Rechtfertigung: philosophische Aufsätze , Frankfurt am Main: Suhrkamp; translated as Truth and Justification , Barbara Fultner (trans.), Cambridge, MA: MIT Press, 2003.
  • –––, 2005, Zwischen Naturalismus und Religion. Philosophische Aufsätze , Frankfurt am Main: Suhrkamp; translated as Between Naturalism and Religion , Ciaran Cronin (trans.), Malden, MA: Polity, 2008.
  • –––, 2006, “Political Communication in Media Society: Does Democracy Still Enjoy an Epistemic Dimension? The Impact of Normative Theory on Empirical Research”, Communication Theory , 16(4): 411–426. doi:10.1111/j.1468-2885.2006.00280.x
  • –––, 2019, Auch eine Geschichte der Philosophie , 2 vols., Berlin: Suhrkamp; part of volume 1 translated as Also a History of Philosophy, Volume 1: The Project of a Genealogy of Postmetaphysical Thinking , Ciaran Cronin (trans.), Cambridge: Polity, 2023.
  • –––, 2021, “Überlegungen und Hypothesen zu einem erneuten Strukturwandel der politischen Öffentlichkeit”, in: Martin Seeliger and Sebastian Sevignani (eds.), Ein neuer Strukturwandel der Öffentlichkeit? , Baden-Baden: Nomos Verlag, 470–500; translated as “Reflections and Hypotheses on a Further Structural Transformation of the Political Public Sphere”, Ciaran Cronin (trans.), Theory, Culture & Society , 39(4) (2022): 145–171. doi:10.1177/02632764221112341
  • Hall, Stuart, 2021, Selected Writings on Race and Difference , Durham, NC: Duke University Press.
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  • –––, 2019, Reconciliation and Reification: Freedom’s Semblance and Actuality from Hegel to Contemporary Critical Theory , Oxford: Oxford University Press.
  • Heberle, Renée (ed.), 2006, Feminist Interpretations of Theodor Adorno , University Park, PA: The Pennsylvania University Press.
  • Honneth, Axel, 1985, Kritik der Macht: Reflexionsstufen einer kritischen Gesellschaftstheorie , Frankfurt am Main: Suhrkamp; translated as Critique of Power: Reflective Stages in a Critical Social Theory , Kenneth Baynes (trans.), Cambridge, MA: MIT Press, 1991.
  • –––, 1992, Kampf um Anerkennung: Zur moralischen Grammatik sozialer Konflikte , Frankfurt am Main: Suhrkamp; translated as The Struggle for Recognition: The Moral Grammar of Social Conflicts , Joel Anderson (trans.), Cambridge: Polity, 1995.
  • –––, 1994, “Die soziale Dynamik von Mißachtung: Zur Ortsbestimmung einer kritischen Gesellschaftstheorie”, Leviathan , 22(1): 78–93; translated as “The Social Dynamics of Disrespect: On the Location of Critical Theory Today”, John Farrell (trans.), Constellations , 1(2): 255–69, reprinted in in Axel Honneth, Disrespect: The Normative Foundations of Critical Theory , Cambridge: Polity Press, 2007, pp. 63–79.
  • –––, 1998, “Über die Möglichkeit einer erschließenden Kritik. Die Dialektik der Aufklärung im Horizont gegenwärtiger Debatten über Sozialkritik”, Paradigmi. Rivista di critica filosofica , 16(48): 501–514; translated as “The Possibility of a Disclosing Critique of Society: The Dialectic of Enlightenment in Light of Current Debates in Social Criticism”, Constellations , 7(1) (2000): 116–127. doi:10.1111/1467-8675.00173
  • –––, 2000, Das Andere der Gerechtigkeit ; translated as Disrespect: The Normative Foundations of Critical Theory , Joseph Ganahl (trans.), Cambridge: Polity, 2007.
  • –––, 2001, Leiden an Unbestimmtheit: Eine Reaktualisierung der Hegelschen Rechtsphilosophie , Stuttgart: Reclam; translated as The Pathologies of Individual Freedom: Hegel’s Social Theory , Ladislaus Löb (trans.), Princeton: Princeton University Press, 2010.
  • –––, 2003, “Redistribution as Recognition”, in N. Fraser and A. Honneth (eds.), Redistribution or Recognition? A Political-Philosophical Exchange , London: Verso, pp. 110–197.
  • –––, 2004, “Eine soziale Pathologie der Vernunft. Zur intellektuellen Erbschaft der Kritischen Theorie”, in Christoph Halbig and Michael Quante (eds.), Axel Honneth: Sozialphilosophie zwischen Kritik und Anerkennung , Münster: LIT-Verlag, pp. 9-32; translated as “A Social Pathology of Reason: On the Intellectual Legacy of Critical Theory”, in A. Honneth , Pathologies of Reason: On the Legacy of Critical Theory , New York: Columbia University Press, 2009, pp. 19-42.
  • –––, 2005, Verdinglichung: Eine anerkennungstheoretische Studie , Frankfurt am Main: Suhrkamp; translated as Reification , Martin Jay (ed.), New York: Oxford University Press, 2008.
  • –––, 2010, Das Ich im Wir: Studien zur Anerkennungstheorie , Berlin: Suhrkamp; translated as The I in We: Studies in the Theory of Recognition , Joseph Ganahl (trans.), Cambridge: Polity, 2012.
  • –––, 2011, Das Recht der Freiheit: Grundriß einer demokratischen Sittlichkeit , Berlin: Suhrkamp; translated as Freedom’s Right: The Social Foundations of Democratic Life , Joseph Ganahl (trans.), New York: Columbia University Press, 2014.
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  • –––, 2022, “‘Labour’, A Brief History of a Modern Concept”, Philosophy , 97(2), 149–167. doi:10.1017/S003181912100036X
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  • Honneth, Axel, and Hans Joas (eds.), 1986, Kommunikatives Handeln: Beiträge zu Jürgen Habermas ‘Theorie des Kommunikativen Handelns , Frankfurt am Main: Suhrkamp; translated as Communicative Action: Essays on Jürgen Habermas’s The Theory of Communicative Action, Jeremy Gaines and Doris L. Jones (trans.), Cambridge, MA: MIT Press, 1991.
  • Horkheimer, Max, 1931, “Die gegenwärtige Lage der Sozialphilosophie und die Aufgaben eines Instituts für Sozialforschung”, Frankfurter Universitätsreden , XXXVII: 3–16; translated as “The Present Situation of Social Philosophy and the Tasks of an Institute for Social Research”, John Torpey (trans.), in Max Horkheimer, Between Philosophy and Social Science: Selected Early Writings , Cambridge, MA: MIT Press, 1993, pp. 1–14. Retranslated as “The State of Contemporary Social Philosophy and the Tasks of an Institute for Social Research”, Journal for Cultural Research , Peter Wagner (trans.), 22(2) (2018): 113–121. doi:10.1080/14797585.2018.1461354
  • –––, 1933, “Materialismus und Moral”, Zeitschrift für Sozialforschung , 2(2): 162–197; translated as “Materialism and Morality”, G. Frederick Hunter (trans.), in Max Horkheimer, Between Philosophy and Social Science: Selected Early Writings , Cambridge: MIT Press, 1993, pp. 15–47.
  • –––, 1936a, “Egoismus und Freiheitsbewegung: Zur Anthropologie des bürgerlichen Zeitalters”, Zeitschrift für Sozialforschung , 5(2): 161–234; translated as “Egoism and Freedom Movements: On the Anthropology of the Bourgeois Era”, G. Frederick Hunter (trans.), in Max Horkheimer, Between Philosophy and Social Science: Selected Early Writings , Cambridge: MIT Press, 1993, pp. 49–110.
  • ––– (ed.), 1936b, Studien über Autorität und Familie: Forschungsberichte aus dem Institut für Sozialforschung , Paris: Librairie Félix Alcan.
  • –––, 1937a, “Traditionelle und kritische Theorie”, Zeitschrift für Sozialforschung , 6(2): 245–294; translated as “Traditional and Critical Theory”, Matthew J. O’Connell (trans.), in Max Horkheimer, Critical Theory: Selected Essays , New York: Continuum, 1972, pp. 188–243.
  • –––, 1937b, “Nachtrag”, Zeitschrift für Sozialforschung , 6(3): 625–631; translated as “Postscript”, Matthew J. O’Connell (trans.), in Max Horkheimer, Critical Theory: Selected Essays , New York: Continuum, 1972, pp. 244–252.
  • –––, 1941, “Art and Mass Culture”, Zeitschrift für Sozialforschung , 9(2), 290–304, republished in Max Horkheimer, Critical Theory: Selected Essays , New York: Continuum, 1972, pp. 273–290.
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  • –––, 2013, Totalitäre Propaganda , Bernd Stiegler (ed.), Berlin: Suhrkamp. Selections are translated as part of “Studies of Totalitarianism, Propaganda, and the Masses (1936–1940)” in Siegfried Kracauer, Selected Writings on Media, Propaganda, and Political Communication , Jaeho Kang, Graeme Gilloch, and John Abromeit (eds.), New York: Columbia University Press, 2022.
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  • –––, 2021, Beyond the Public Sphere: Film and the Feminist Imaginary , Evanston, IL: Northwestern University Press.
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  • –––, 1967, “Liberation from the Affluent Society” in Douglas Kellner (ed.), The New Left and the 1960s: Collected Papers of Herbert Marcuse, Volume 3 , New York: Routledge, 2004.
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  • –––, 1844, “Zur Kritik der Hegelschen Rechtsphilosophie: Einleitung”, in Karl Marx: Werke, Artikel, Entwürfe: März 1843 – August 1944 (Karl Marx/Friedrich Engels Gesamtausgabe, vol. I.2), Berlin: Dietz, 1975, pp. 170–184; translated as “Contribution to the Critique of Hegel’s Philosophy of Law”, Martin Milligan and Barbara Ruhemann (trans.), in Karl Marx March 1843 – August 1944 (Karl Marx/Friedrich Engels Collected Works, vol. 3), London: Lawrence and Wishart, 1975, pp. 3–127.
  • –––, 1846, Die deutsche Ideologie: Manuskripte und Drucke (Karl Marx/Friedrich Engels Gesamtausgabe, vol. I.5), Berlin: De Gruyter/Akademie, 2017; translated as The German Ideology (Karl Marx/Friedrich Engels Collected Works, vol. 5), Clemens Dutt, W. Lough, and C. P. Magill (trans.), London: Lawrence and Wishart, 1976.
  • –––, 1867, Das Kapital: Kritik der politischen Ökonomie. Erster Band (Hamburg 1867) (Karl Marx/Friedrich Engels Gesamtausgabe, vol. II.5), Berlin: Dietz, 1983; translated as Capital, Volume I (Karl Marx/Friedrich Engels Collected Works, vol. 35), London: Lawrence and Wishart, 1996.
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Acknowledgments

The authors would like to thank Amy Allen, Axel Honneth, Noëlle McAfee, and Martin Saar for their very helpful comments on earlier drafts and Christian Meyer for judicious editorial assistance.

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The Critical Period Hypothesis in Second Language Acquisition: A Statistical Critique and a Reanalysis

Jan vanhove.

Department of Multilingualism, University of Fribourg, Fribourg, Switzerland

Analyzed the data: JV. Wrote the paper: JV.

Associated Data

In second language acquisition research, the critical period hypothesis ( cph ) holds that the function between learners' age and their susceptibility to second language input is non-linear. This paper revisits the indistinctness found in the literature with regard to this hypothesis's scope and predictions. Even when its scope is clearly delineated and its predictions are spelt out, however, empirical studies–with few exceptions–use analytical (statistical) tools that are irrelevant with respect to the predictions made. This paper discusses statistical fallacies common in cph research and illustrates an alternative analytical method (piecewise regression) by means of a reanalysis of two datasets from a 2010 paper purporting to have found cross-linguistic evidence in favour of the cph . This reanalysis reveals that the specific age patterns predicted by the cph are not cross-linguistically robust. Applying the principle of parsimony, it is concluded that age patterns in second language acquisition are not governed by a critical period. To conclude, this paper highlights the role of confirmation bias in the scientific enterprise and appeals to second language acquisition researchers to reanalyse their old datasets using the methods discussed in this paper. The data and R commands that were used for the reanalysis are provided as supplementary materials.

Introduction

In the long term and in immersion contexts, second-language (L2) learners starting acquisition early in life – and staying exposed to input and thus learning over several years or decades – undisputedly tend to outperform later learners. Apart from being misinterpreted as an argument in favour of early foreign language instruction, which takes place in wholly different circumstances, this general age effect is also sometimes taken as evidence for a so-called ‘critical period’ ( cp ) for second-language acquisition ( sla ). Derived from biology, the cp concept was famously introduced into the field of language acquisition by Penfield and Roberts in 1959 [1] and was refined by Lenneberg eight years later [2] . Lenneberg argued that language acquisition needed to take place between age two and puberty – a period which he believed to coincide with the lateralisation process of the brain. (More recent neurological research suggests that different time frames exist for the lateralisation process of different language functions. Most, however, close before puberty [3] .) However, Lenneberg mostly drew on findings pertaining to first language development in deaf children, feral children or children with serious cognitive impairments in order to back up his claims. For him, the critical period concept was concerned with the implicit “automatic acquisition” [2, p. 176] in immersion contexts and does not preclude the possibility of learning a foreign language after puberty, albeit with much conscious effort and typically less success.

sla research adopted the critical period hypothesis ( cph ) and applied it to second and foreign language learning, resulting in a host of studies. In its most general version, the cph for sla states that the ‘susceptibility’ or ‘sensitivity’ to language input varies as a function of age, with adult L2 learners being less susceptible to input than child L2 learners. Importantly, the age–susceptibility function is hypothesised to be non-linear. Moving beyond this general version, we find that the cph is conceptualised in a multitude of ways [4] . This state of affairs requires scholars to make explicit their theoretical stance and assumptions [5] , but has the obvious downside that critical findings risk being mitigated as posing a problem to only one aspect of one particular conceptualisation of the cph , whereas other conceptualisations remain unscathed. This overall vagueness concerns two areas in particular, viz. the delineation of the cph 's scope and the formulation of testable predictions. Delineating the scope and formulating falsifiable predictions are, needless to say, fundamental stages in the scientific evaluation of any hypothesis or theory, but the lack of scholarly consensus on these points seems to be particularly pronounced in the case of the cph . This article therefore first presents a brief overview of differing views on these two stages. Then, once the scope of their cph version has been duly identified and empirical data have been collected using solid methods, it is essential that researchers analyse the data patterns soundly in order to assess the predictions made and that they draw justifiable conclusions from the results. As I will argue in great detail, however, the statistical analysis of data patterns as well as their interpretation in cph research – and this includes both critical and supportive studies and overviews – leaves a great deal to be desired. Reanalysing data from a recent cph -supportive study, I illustrate some common statistical fallacies in cph research and demonstrate how one particular cph prediction can be evaluated.

Delineating the scope of the critical period hypothesis

First, the age span for a putative critical period for language acquisition has been delimited in different ways in the literature [4] . Lenneberg's critical period stretched from two years of age to puberty (which he posits at about 14 years of age) [2] , whereas other scholars have drawn the cutoff point at 12, 15, 16 or 18 years of age [6] . Unlike Lenneberg, most researchers today do not define a starting age for the critical period for language learning. Some, however, consider the possibility of the critical period (or a critical period for a specific language area, e.g. phonology) ending much earlier than puberty (e.g. age 9 years [1] , or as early as 12 months in the case of phonology [7] ).

Second, some vagueness remains as to the setting that is relevant to the cph . Does the critical period constrain implicit learning processes only, i.e. only the untutored language acquisition in immersion contexts or does it also apply to (at least partly) instructed learning? Most researchers agree on the former [8] , but much research has included subjects who have had at least some instruction in the L2.

Third, there is no consensus on what the scope of the cp is as far as the areas of language that are concerned. Most researchers agree that a cp is most likely to constrain the acquisition of pronunciation and grammar and, consequently, these are the areas primarily looked into in studies on the cph [9] . Some researchers have also tried to define distinguishable cp s for the different language areas of phonetics, morphology and syntax and even for lexis (see [10] for an overview).

Fourth and last, research into the cph has focused on ‘ultimate attainment’ ( ua ) or the ‘final’ state of L2 proficiency rather than on the rate of learning. From research into the rate of acquisition (e.g. [11] – [13] ), it has become clear that the cph cannot hold for the rate variable. In fact, it has been observed that adult learners proceed faster than child learners at the beginning stages of L2 acquisition. Though theoretical reasons for excluding the rate can be posited (the initial faster rate of learning in adults may be the result of more conscious cognitive strategies rather than to less conscious implicit learning, for instance), rate of learning might from a different perspective also be considered an indicator of ‘susceptibility’ or ‘sensitivity’ to language input. Nevertheless, contemporary sla scholars generally seem to concur that ua and not rate of learning is the dependent variable of primary interest in cph research. These and further scope delineation problems relevant to cph research are discussed in more detail by, among others, Birdsong [9] , DeKeyser and Larson-Hall [14] , Long [10] and Muñoz and Singleton [6] .

Formulating testable hypotheses

Once the relevant cph 's scope has satisfactorily been identified, clear and testable predictions need to be drawn from it. At this stage, the lack of consensus on what the consequences or the actual observable outcome of a cp would have to look like becomes evident. As touched upon earlier, cph research is interested in the end state or ‘ultimate attainment’ ( ua ) in L2 acquisition because this “determines the upper limits of L2 attainment” [9, p. 10]. The range of possible ultimate attainment states thus helps researchers to explore the potential maximum outcome of L2 proficiency before and after the putative critical period.

One strong prediction made by some cph exponents holds that post- cp learners cannot reach native-like L2 competences. Identifying a single native-like post- cp L2 learner would then suffice to falsify all cph s making this prediction. Assessing this prediction is difficult, however, since it is not clear what exactly constitutes sufficient nativelikeness, as illustrated by the discussion on the actual nativelikeness of highly accomplished L2 speakers [15] , [16] . Indeed, there exists a real danger that, in a quest to vindicate the cph , scholars set the bar for L2 learners to match monolinguals increasingly higher – up to Swiftian extremes. Furthermore, the usefulness of comparing the linguistic performance in mono- and bilinguals has been called into question [6] , [17] , [18] . Put simply, the linguistic repertoires of mono- and bilinguals differ by definition and differences in the behavioural outcome will necessarily be found, if only one digs deep enough.

A second strong prediction made by cph proponents is that the function linking age of acquisition and ultimate attainment will not be linear throughout the whole lifespan. Before discussing how this function would have to look like in order for it to constitute cph -consistent evidence, I point out that the ultimate attainment variable can essentially be considered a cumulative measure dependent on the actual variable of interest in cph research, i.e. susceptibility to language input, as well as on such other factors like duration and intensity of learning (within and outside a putative cp ) and possibly a number of other influencing factors. To elaborate, the behavioural outcome, i.e. ultimate attainment, can be assumed to be integrative to the susceptibility function, as Newport [19] correctly points out. Other things being equal, ultimate attainment will therefore decrease as susceptibility decreases. However, decreasing ultimate attainment levels in and by themselves represent no compelling evidence in favour of a cph . The form of the integrative curve must therefore be predicted clearly from the susceptibility function. Additionally, the age of acquisition–ultimate attainment function can take just about any form when other things are not equal, e.g. duration of learning (Does learning last up until time of testing or only for a more or less constant number of years or is it dependent on age itself?) or intensity of learning (Do learners always learn at their maximum susceptibility level or does this intensity vary as a function of age, duration, present attainment and motivation?). The integral of the susceptibility function could therefore be of virtually unlimited complexity and its parameters could be adjusted to fit any age of acquisition–ultimate attainment pattern. It seems therefore astonishing that the distinction between level of sensitivity to language input and level of ultimate attainment is rarely made in the literature. Implicitly or explicitly [20] , the two are more or less equated and the same mathematical functions are expected to describe the two variables if observed across a range of starting ages of acquisition.

But even when the susceptibility and ultimate attainment variables are equated, there remains controversy as to what function linking age of onset of acquisition and ultimate attainment would actually constitute evidence for a critical period. Most scholars agree that not any kind of age effect constitutes such evidence. More specifically, the age of acquisition–ultimate attainment function would need to be different before and after the end of the cp [9] . According to Birdsong [9] , three basic possible patterns proposed in the literature meet this condition. These patterns are presented in Figure 1 . The first pattern describes a steep decline of the age of onset of acquisition ( aoa )–ultimate attainment ( ua ) function up to the end of the cp and a practically non-existent age effect thereafter. Pattern 2 is an “unconventional, although often implicitly invoked” [9, p. 17] notion of the cp function which contains a period of peak attainment (or performance at ceiling), i.e. performance does not vary as a function of age, which is often referred to as a ‘window of opportunity’. This time span is followed by an unbounded decline in ua depending on aoa . Pattern 3 includes characteristics of patterns 1 and 2. At the beginning of the aoa range, performance is at ceiling. The next segment is a downward slope in the age function which ends when performance reaches its floor. Birdsong points out that all of these patterns have been reported in the literature. On closer inspection, however, he concludes that the most convincing function describing these age effects is a simple linear one. Hakuta et al. [21] sketch further theoretically possible predictions of the cph in which the mean performance drops drastically and/or the slope of the aoa – ua proficiency function changes at a certain point.

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The graphs are based on based on Figure 2 in [9] .

Although several patterns have been proposed in the literature, it bears pointing out that the most common explicit prediction corresponds to Birdsong's first pattern, as exemplified by the following crystal-clear statement by DeKeyser, one of the foremost cph proponents:

[A] strong negative correlation between age of acquisition and ultimate attainment throughout the lifespan (or even from birth through middle age), the only age effect documented in many earlier studies, is not evidence for a critical period…[T]he critical period concept implies a break in the AoA–proficiency function, i.e., an age (somewhat variable from individual to individual, of course, and therefore an age range in the aggregate) after which the decline of success rate in one or more areas of language is much less pronounced and/or clearly due to different reasons. [22, p. 445].

DeKeyser and before him among others Johnson and Newport [23] thus conceptualise only one possible pattern which would speak in favour of a critical period: a clear negative age effect before the end of the critical period and a much weaker (if any) negative correlation between age and ultimate attainment after it. This ‘flattened slope’ prediction has the virtue of being much more tangible than the ‘potential nativelikeness’ prediction: Testing it does not necessarily require comparing the L2-learners to a native control group and thus effectively comparing apples and oranges. Rather, L2-learners with different aoa s can be compared amongst themselves without the need to categorise them by means of a native-speaker yardstick, the validity of which is inevitably going to be controversial [15] . In what follows, I will concern myself solely with the ‘flattened slope’ prediction, arguing that, despite its clarity of formulation, cph research has generally used analytical methods that are irrelevant for the purposes of actually testing it.

Inferring non-linearities in critical period research: An overview

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Group mean or proportion comparisons

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[T]he main differences can be found between the native group and all other groups – including the earliest learner group – and between the adolescence group and all other groups. However, neither the difference between the two childhood groups nor the one between the two adulthood groups reached significance, which indicates that the major changes in eventual perceived nativelikeness of L2 learners can be associated with adolescence. [15, p. 270].

Similar group comparisons aimed at investigating the effect of aoa on ua have been carried out by both cph advocates and sceptics (among whom Bialystok and Miller [25, pp. 136–139], Birdsong and Molis [26, p. 240], Flege [27, pp. 120–121], Flege et al. [28, pp. 85–86], Johnson [29, p. 229], Johnson and Newport [23, p. 78], McDonald [30, pp. 408–410] and Patowski [31, pp. 456–458]). To be clear, not all of these authors drew direct conclusions about the aoa – ua function on the basis of these groups comparisons, but their group comparisons have been cited as indicative of a cph -consistent non-continuous age effect, as exemplified by the following quote by DeKeyser [22] :

Where group comparisons are made, younger learners always do significantly better than the older learners. The behavioral evidence, then, suggests a non-continuous age effect with a “bend” in the AoA–proficiency function somewhere between ages 12 and 16. [22, p. 448].

The first problem with group comparisons like these and drawing inferences on the basis thereof is that they require that a continuous variable, aoa , be split up into discrete bins. More often than not, the boundaries between these bins are drawn in an arbitrary fashion, but what is more troublesome is the loss of information and statistical power that such discretisation entails (see [32] for the extreme case of dichotomisation). If we want to find out more about the relationship between aoa and ua , why throw away most of the aoa information and effectively reduce the ua data to group means and the variance in those groups?

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Comparison of correlation coefficients

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Correlation-based inferences about slope discontinuities have similarly explicitly been made by cph advocates and skeptics alike, e.g. Bialystok and Miller [25, pp. 136 and 140], DeKeyser and colleagues [22] , [44] and Flege et al. [45, pp. 166 and 169]. Others did not explicitly infer the presence or absence of slope differences from the subset correlations they computed (among others Birdsong and Molis [26] , DeKeyser [8] , Flege et al. [28] and Johnson [29] ), but their studies nevertheless featured in overviews discussing discontinuities [14] , [22] . Indeed, the most recent overview draws a strong conclusion about the validity of the cph 's ‘flattened slope’ prediction on the basis of these subset correlations:

In those studies where the two groups are described separately, the correlation is much higher for the younger than for the older group, except in Birdsong and Molis (2001) [ =  [26] , JV], where there was a ceiling effect for the younger group. This global picture from more than a dozen studies provides support for the non-continuity of the decline in the AoA–proficiency function, which all researchers agree is a hallmark of a critical period phenomenon. [22, p. 448].

In Johnson and Newport's specific case [23] , their correlation-based inference that ua levels off after puberty happened to be largely correct: the gjt scores are more or less randomly distributed around a near-horizontal trend line [26] . Ultimately, however, it rests on the fallacy of confusing correlation coefficients with slopes, which seriously calls into question conclusions such as DeKeyser's (cf. the quote above).

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It can then straightforwardly be deduced that, other things equal, the aoa – ua correlation in the older group decreases as the ua variance in the older group increases relative to the ua variance in the younger group (Eq. 3).

equation image

Lower correlation coefficients in older aoa groups may therefore be largely due to differences in ua variance, which have been reported in several studies [23] , [26] , [28] , [29] (see [46] for additional references). Greater variability in ua with increasing age is likely due to factors other than age proper [47] , such as the concomitant greater variability in exposure to literacy, degree of education, motivation and opportunity for language use, and by itself represents evidence neither in favour of nor against the cph .

Regression approaches

Having demonstrated that neither group mean or proportion comparisons nor correlation coefficient comparisons can directly address the ‘flattened slope’ prediction, I now turn to the studies in which regression models were computed with aoa as a predictor variable and ua as the outcome variable. Once again, this category of studies is not mutually exclusive with the two categories discussed above.

In a large-scale study using self-reports and approximate aoa s derived from a sample of the 1990 U.S. Census, Stevens found that the probability with which immigrants from various countries stated that they spoke English ‘very well’ decreased curvilinearly as a function of aoa [48] . She noted that this development is similar to the pattern found by Johnson and Newport [23] but that it contains no indication of an “abruptly defined ‘critical’ or sensitive period in L2 learning” [48, p. 569]. However, she modelled the self-ratings using an ordinal logistic regression model in which the aoa variable was logarithmically transformed. Technically, this is perfectly fine, but one should be careful not to read too much into the non-linear curves found. In logistic models, the outcome variable itself is modelled linearly as a function of the predictor variables and is expressed in log-odds. In order to compute the corresponding probabilities, these log-odds are transformed using the logistic function. Consequently, even if the model is specified linearly, the predicted probabilities will not lie on a perfectly straight line when plotted as a function of any one continuous predictor variable. Similarly, when the predictor variable is first logarithmically transformed and then used to linearly predict an outcome variable, the function linking the predicted outcome variables and the untransformed predictor variable is necessarily non-linear. Thus, non-linearities follow naturally from Stevens's model specifications. Moreover, cph -consistent discontinuities in the aoa – ua function cannot be found using her model specifications as they did not contain any parameters allowing for this.

Using data similar to Stevens's, Bialystok and Hakuta found that the link between the self-rated English competences of Chinese- and Spanish-speaking immigrants and their aoa could be described by a straight line [49] . In contrast to Stevens, Bialystok and Hakuta used a regression-based method allowing for changes in the function's slope, viz. locally weighted scatterplot smoothing ( lowess ). Informally, lowess is a non-parametrical method that relies on an algorithm that fits the dependent variable for small parts of the range of the independent variable whilst guaranteeing that the overall curve does not contain sudden jumps (for technical details, see [50] ). Hakuta et al. used an even larger sample from the same 1990 U.S. Census data on Chinese- and Spanish-speaking immigrants (2.3 million observations) [21] . Fitting lowess curves, no discontinuities in the aoa – ua slope could be detected. Moreover, the authors found that piecewise linear regression models, i.e. regression models containing a parameter that allows a sudden drop in the curve or a change of its slope, did not provide a better fit to the data than did an ordinary regression model without such a parameter.

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To sum up, I have argued at length that regression approaches are superior to group mean and correlation coefficient comparisons for the purposes of testing the ‘flattened slope’ prediction. Acknowledging the reservations vis-à-vis self-estimated ua s, we still find that while the relationship between aoa and ua is not necessarily perfectly linear in the studies discussed, the data do not lend unequivocal support to this prediction. In the following section, I will reanalyse data from a recent empirical paper on the cph by DeKeyser et al. [44] . The first goal of this reanalysis is to further illustrate some of the statistical fallacies encountered in cph studies. Second, by making the computer code available I hope to demonstrate how the relevant regression models, viz. piecewise regression models, can be fitted and how the aoa representing the optimal breakpoint can be identified. Lastly, the findings of this reanalysis will contribute to our understanding of how aoa affects ua as measured using a gjt .

Summary of DeKeyser et al. (2010)

I chose to reanalyse a recent empirical paper on the cph by DeKeyser et al. [44] (henceforth DK et al.). This paper lends itself well to a reanalysis since it exhibits two highly commendable qualities: the authors spell out their hypotheses lucidly and provide detailed numerical and graphical data descriptions. Moreover, the paper's lead author is very clear on what constitutes a necessary condition for accepting the cph : a non-linearity in the age of onset of acquisition ( aoa )–ultimate attainment ( ua ) function, with ua declining less strongly as a function of aoa in older, post- cp arrivals compared to younger arrivals [14] , [22] . Lastly, it claims to have found cross-linguistic evidence from two parallel studies backing the cph and should therefore be an unsuspected source to cph proponents.

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The authors set out to test the following hypotheses:

  • Hypothesis 1: For both the L2 English and the L2 Hebrew group, the slope of the age of arrival–ultimate attainment function will not be linear throughout the lifespan, but will instead show a marked flattening between adolescence and adulthood.
  • Hypothesis 2: The relationship between aptitude and ultimate attainment will differ markedly for the young and older arrivals, with significance only for the latter. (DK et al., p. 417)

Both hypotheses were purportedly confirmed, which in the authors' view provides evidence in favour of cph . The problem with this conclusion, however, is that it is based on a comparison of correlation coefficients. As I have argued above, correlation coefficients are not to be confused with regression coefficients and cannot be used to directly address research hypotheses concerning slopes, such as Hypothesis 1. In what follows, I will reanalyse the relationship between DK et al.'s aoa and gjt data in order to address Hypothesis 1. Additionally, I will lay bare a problem with the way in which Hypothesis 2 was addressed. The extracted data and the computer code used for the reanalysis are provided as supplementary materials, allowing anyone interested to scrutinise and easily reproduce my whole analysis and carry out their own computations (see ‘supporting information’).

Data extraction

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In order to verify whether we did in fact extract the data points to a satisfactory degree of accuracy, I computed summary statistics for the extracted aoa and gjt data and checked these against the descriptive statistics provided by DK et al. (pp. 421 and 427). These summary statistics for the extracted data are presented in Table 1 . In addition, I computed the correlation coefficients for the aoa – gjt relationship for the whole aoa range and for aoa -defined subgroups and checked these coefficients against those reported by DK et al. (pp. 423 and 428). The correlation coefficients computed using the extracted data are presented in Table 2 . Both checks strongly suggest the extracted data to be virtually identical to the original data, and Dr DeKeyser confirmed this to be the case in response to an earlier draft of the present paper (personal communication, 6 May 2013).

Results and Discussion

Modelling the link between age of onset of acquisition and ultimate attainment.

I first replotted the aoa and gjt data we extracted from DK et al.'s scatterplots and added non-parametric scatterplot smoothers in order to investigate whether any changes in slope in the aoa – gjt function could be revealed, as per Hypothesis 1. Figures 3 and ​ and4 4 show this not to be the case. Indeed, simple linear regression models that model gjt as a function of aoa provide decent fits for both the North America and the Israel data, explaining 65% and 63% of the variance in gjt scores, respectively. The parameters of these models are given in Table 3 .

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The trend line is a non-parametric scatterplot smoother. The scatterplot itself is a near-perfect replication of DK et al.'s Fig. 1.

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The trend line is a non-parametric scatterplot smoother. The scatterplot itself is a near-perfect replication of DK et al.'s Fig. 5.

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To ensure that both segments are joined at the breakpoint, the predictor variable is first centred at the breakpoint value, i.e. the breakpoint value is subtracted from the original predictor variable values. For a blow-by-blow account of how such models can be fitted in r , I refer to an example analysis by Baayen [55, pp. 214–222].

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Solid: regression with breakpoint at aoa 18 (dashed lines represent its 95% confidence interval); dot-dash: regression without breakpoint.

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Solid: regression with breakpoint at aoa 18 (dashed lines represent its 95% confidence interval); dot-dash (hardly visible due to near-complete overlap): regression without breakpoint.

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Solid: regression with breakpoint at aoa 16 (dashed lines represent its 95% confidence interval); dot-dash: regression without breakpoint.

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Solid: regression with breakpoint at aoa 6 (dashed lines represent its 95% confidence interval); dot-dash (hardly visible due to near-complete overlap): regression without breakpoint.

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In sum, a regression model that allows for changes in the slope of the the aoa – gjt function to account for putative critical period effects provides a somewhat better fit to the North American data than does an everyday simple regression model. The improvement in model fit is marginal, however, and including a breakpoint does not result in any detectable improvement of model fit to the Israel data whatsoever. Breakpoint models therefore fail to provide solid cross-linguistic support in favour of critical period effects: across both data sets, gjt can satisfactorily be modelled as a linear function of aoa .

On partialling out ‘age at testing’

As I have argued above, correlation coefficients cannot be used to test hypotheses about slopes. When the correct procedure is carried out on DK et al.'s data, no cross-linguistically robust evidence for changes in the aoa – gjt function was found. In addition to comparing the zero-order correlations between aoa and gjt , however, DK et al. computed partial correlations in which the variance in aoa associated with the participants' age at testing ( aat ; a potentially confounding variable) was filtered out. They found that these partial correlations between aoa and gjt , which are given in Table 9 , differed between age groups in that they are stronger for younger than for older participants. This, DK et al. argue, constitutes additional evidence in favour of the cph . At this point, I can no longer provide my own analysis of DK et al.'s data seeing as the pertinent data points were not plotted. Nevertheless, the detailed descriptions by DK et al. strongly suggest that the use of these partial correlations is highly problematic. Most importantly, and to reiterate, correlations (whether zero-order or partial ones) are actually of no use when testing hypotheses concerning slopes. Still, one may wonder why the partial correlations differ across age groups. My surmise is that these differences are at least partly the by-product of an imbalance in the sampling procedure.

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The upshot of this brief discussion is that the partial correlation differences reported by DK et al. are at least partly the result of an imbalance in the sampling procedure: aoa and aat were simply less intimately tied for the young arrivals in the North America study than for the older arrivals with L2 English or for all of the L2 Hebrew participants. In an ideal world, we would like to fix aat or ascertain that it at most only weakly correlates with aoa . This, however, would result in a strong correlation between aoa and another potential confound variable, length of residence in the L2 environment, bringing us back to square one. Allowing for only moderate correlations between aoa and aat might improve our predicament somewhat, but even in that case, we should tread lightly when making inferences on the basis of statistical control procedures [61] .

On estimating the role of aptitude

Having shown that Hypothesis 1 could not be confirmed, I now turn to Hypothesis 2, which predicts a differential role of aptitude for ua in sla in different aoa groups. More specifically, it states that the correlation between aptitude and gjt performance will be significant only for older arrivals. The correlation coefficients of the relationship between aptitude and gjt are presented in Table 10 .

The problem with both the wording of Hypothesis 2 and the way in which it is addressed is the following: it is assumed that a variable has a reliably different effect in different groups when the effect reaches significance in one group but not in the other. This logic is fairly widespread within several scientific disciplines (see e.g. [62] for a discussion). Nonetheless, it is demonstrably fallacious [63] . Here we will illustrate the fallacy for the specific case of comparing two correlation coefficients.

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Apart from not being replicated in the North America study, does this difference actually show anything? I contend that it does not: what is of interest are not so much the correlation coefficients, but rather the interactions between aoa and aptitude in models predicting gjt . These interactions could be investigated by fitting a multiple regression model in which the postulated cp breakpoint governs the slope of both aoa and aptitude. If such a model provided a substantially better fit to the data than a model without a breakpoint for the aptitude slope and if the aptitude slope changes in the expected direction (i.e. a steeper slope for post- cp than for younger arrivals) for different L1–L2 pairings, only then would this particular prediction of the cph be borne out.

Using data extracted from a paper reporting on two recent studies that purport to provide evidence in favour of the cph and that, according to its authors, represent a major improvement over earlier studies (DK et al., p. 417), it was found that neither of its two hypotheses were actually confirmed when using the proper statistical tools. As a matter of fact, the gjt scores continue to decline at essentially the same rate even beyond the end of the putative critical period. According to the paper's lead author, such a finding represents a serious problem to his conceptualisation of the cph [14] ). Moreover, although modelling a breakpoint representing the end of a cp at aoa 16 may improve the statistical model slightly in study on learners of English in North America, the study on learners of Hebrew in Israel fails to confirm this finding. In fact, even if we were to accept the optimal breakpoint computed for the Israel study, it lies at aoa 6 and is associated with a different geometrical pattern.

Diverging age trends in parallel studies with participants with different L2s have similarly been reported by Birdsong and Molis [26] and are at odds with an L2-independent cph . One parsimonious explanation of such conflicting age trends may be that the overall, cross-linguistic age trend is in fact linear, but that fluctuations in the data (due to factors unaccounted for or randomness) may sometimes give rise to a ‘stretched L’-shaped pattern ( Figure 1, left panel ) and sometimes to a ‘stretched 7’-shaped pattern ( Figure 1 , middle panel; see also [66] for a similar comment).

Importantly, the criticism that DeKeyser and Larsson-Hall levy against two studies reporting findings similar to the present [48] , [49] , viz. that the data consisted of self-ratings of questionable validity [14] , does not apply to the present data set. In addition, DK et al. did not exclude any outliers from their analyses, so I assume that DeKeyser and Larsson-Hall's criticism [14] of Birdsong and Molis's study [26] , i.e. that the findings were due to the influence of outliers, is not applicable to the present data either. For good measure, however, I refitted the regression models with and without breakpoints after excluding one potentially problematic data point per model. The following data points had absolute standardised residuals larger than 2.5 in the original models without breakpoints as well as in those with breakpoints: the participant with aoa 17 and a gjt score of 125 in the North America study and the participant with aoa 12 and a gjt score of 117 in the Israel study. The resultant models were virtually identical to the original models (see Script S1 ). Furthermore, the aoa variable was sufficiently fine-grained and the aoa – gjt curve was not ‘presmoothed’ by the prior aggregation of gjt across parts of the aoa range (see [51] for such a criticism of another study). Lastly, seven of the nine “problems with supposed counter-evidence” to the cph discussed by Long [5] do not apply either, viz. (1) “[c]onfusion of rate and ultimate attainment”, (2) “[i]nappropriate choice of subjects”, (3) “[m]easurement of AO”, (4) “[l]eading instructions to raters”, (6) “[u]se of markedly non-native samples making near-native samples more likely to sound native to raters”, (7) “[u]nreliable or invalid measures”, and (8) “[i]nappropriate L1–L2 pairings”. Problem No. 5 (“Assessments based on limited samples and/or “language-like” behavior”) may be apropos given that only gjt data were used, leaving open the theoretical possibility that other measures might have yielded a different outcome. Finally, problem No. 9 (“Faulty interpretation of statistical patterns”) is, of course, precisely what I have turned the spotlights on.

Conclusions

The critical period hypothesis remains a hotly contested issue in the psycholinguistics of second-language acquisition. Discussions about the impact of empirical findings on the tenability of the cph generally revolve around the reliability of the data gathered (e.g. [5] , [14] , [22] , [52] , [67] , [68] ) and such methodological critiques are of course highly desirable. Furthermore, the debate often centres on the question of exactly what version of the cph is being vindicated or debunked. These versions differ mainly in terms of its scope, specifically with regard to the relevant age span, setting and language area, and the testable predictions they make. But even when the cph 's scope is clearly demarcated and its main prediction is spelt out lucidly, the issue remains to what extent the empirical findings can actually be marshalled in support of the relevant cph version. As I have shown in this paper, empirical data have often been taken to support cph versions predicting that the relationship between age of acquisition and ultimate attainment is not strictly linear, even though the statistical tools most commonly used (notably group mean and correlation coefficient comparisons) were, crudely put, irrelevant to this prediction. Methods that are arguably valid, e.g. piecewise regression and scatterplot smoothing, have been used in some studies [21] , [26] , [49] , but these studies have been criticised on other grounds. To my knowledge, such methods have never been used by scholars who explicitly subscribe to the cph .

I suspect that what may be going on is a form of ‘confirmation bias’ [69] , a cognitive bias at play in diverse branches of human knowledge seeking: Findings judged to be consistent with one's own hypothesis are hardly questioned, whereas findings inconsistent with one's own hypothesis are scrutinised much more strongly and criticised on all sorts of points [70] – [73] . My reanalysis of DK et al.'s recent paper may be a case in point. cph exponents used correlation coefficients to address their prediction about the slope of a function, as had been done in a host of earlier studies. Finding a result that squared with their expectations, they did not question the technical validity of their results, or at least they did not report this. (In fact, my reanalysis is actually a case in point in two respects: for an earlier draft of this paper, I had computed the optimal position of the breakpoints incorrectly, resulting in an insignificant improvement of model fit for the North American data rather than a borderline significant one. Finding a result that squared with my expectations, I did not question the technical validity of my results – until this error was kindly pointed out to me by Martijn Wieling (University of Tübingen).) That said, I am keen to point out that the statistical analyses in this particular paper, though suboptimal, are, as far as I could gather, reported correctly, i.e. the confirmation bias does not seem to have resulted in the blatant misreportings found elsewhere (see [74] for empirical evidence and discussion). An additional point to these authors' credit is that, apart from explicitly identifying their cph version's scope and making crystal-clear predictions, they present data descriptions that actually permit quantitative reassessments and have a history of doing so (e.g. the appendix in [8] ). This leads me to believe that they analysed their data all in good conscience and to hope that they, too, will conclude that their own data do not, in fact, support their hypothesis.

I end this paper on an upbeat note. Even though I have argued that the analytical tools employed in cph research generally leave much to be desired, the original data are, so I hope, still available. This provides researchers, cph supporters and sceptics alike, with an exciting opportunity to reanalyse their data sets using the tools outlined in the present paper and publish their findings at minimal cost of time and resources (for instance, as a comment to this paper). I would therefore encourage scholars to engage their old data sets and to communicate their analyses openly, e.g. by voluntarily publishing their data and computer code alongside their articles or comments. Ideally, cph supporters and sceptics would join forces to agree on a protocol for a high-powered study in order to provide a truly convincing answer to a core issue in sla .

Supporting Information

aoa and gjt data extracted from DeKeyser et al.'s North America study.

aoa and gjt data extracted from DeKeyser et al.'s Israel study.

Script with annotated R code used for the reanalysis. All add-on packages used can be installed from within R.

Acknowledgments

I would like to thank Irmtraud Kaiser (University of Fribourg) for helping me to get an overview of the literature on the critical period hypothesis in second language acquisition. Thanks are also due to Martijn Wieling (currently University of Tübingen) for pointing out an error in the R code accompanying an earlier draft of this paper.

Funding Statement

No current external funding sources for this study.

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Encyclopedia of Sciences and Religions pp 558–560 Cite as

Critical Theory

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Critical theory is a school of thought that stresses the examination and critique of society and culture, drawing from knowledge across the social sciences and philosophy. Critical theory aims at explaining and transforming the circumstances that enslave human beings, as Max Horkheimer defined the term in his now famous 1937 article Traditional and Critical Theory . Critical theory in most of its main form has at least two main elements. Firstly, it is held that empirical study and philosophical analysis should be brought together to form a detailed and correct understanding of a phenomenon under study. Secondly, it is held that the normative basis for the critical research and critique should be founded on the needs, longings, and moral demands of the people living under the conditions of the system or structure that are criticized.

The above definition leads to two different ways to articulate critical theory: one a narrow sense and...

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Critical Period In Brain Development and Childhood Learning

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Key Takeaways

  • Critical period is an ethological term that refers to a fixed and crucial time during the early development of an organism when it can learn things that are essential to survival. These influences impact the development of processes such as hearing and vision, social bonding, and language learning.
  • The term is most often experienced in the study of imprinting, where it is thought that young birds could only develop an attachment to the mother during a fixed time soon after hatching.
  • Neurologically, critical periods are marked by high levels of plasticity in the brain before neural connections become more solidified and stable. In particular, critical periods tend to end when synapses that inhibit the neurotransmitter GABA mature.
  • In contrast to critical periods, sensitive periods, otherwise known as “weak critical periods,” happen when an organism is more sensitive than usual to outside factors influencing behavior, but this influence is not necessarily restricted to the sensitive period.
  • Scholars have debated the extent to which older organisms can develop certain skills, such as natively-accented foreign languages, after the critical period.

brain critical development

The critical period is a biologically determined stage of development where an organism is optimally ready to acquire some pattern of behavior that is part of typical development. This period, by definition, will not recur at a later stage.

If an organism does not receive exposure to the appropriate stimulus needed to learn a skill during a critical period, it may be difficult or even impossible for that organism to develop certain functions associated with that skill later in life.

This happens because a range of functional and structural elements prevent passive experiences from eliciting significant changes in the brain (Cisneros-Franco et al., 2020).

The first strong proponent of the theory of critical periods was Charles Stockhard (1921), a biologist who attempted to experiment with the effects of various chemicals on the development of fish embryos, though he gave credit to Dareste for originating the idea 30 years earlier (Scott, 1962).

Stockhard’s experiments showed that applying almost any chemical to fish embryos at a certain stage of development would result in one-eyed fish.

These experiments established that the most rapidly growing tissues in an embryo are the most sensitive to any change in conditions, leading to effects later in development (Scott, 1962).

Meanwhile, psychologist Sigmund Freud attempted to explain the origins of neurosis in human patients as the result of early experiences, implying that infants are particularly sensitive to influences at certain points in their lives.

Lorenz (1935) later emphasized the importance of critical periods in the formation of primary social bonds (otherwise known as imprinting) in birds, remarking that this psychological imprinting was similar to critical periods in the development of the embryo.

Soon thereafter, McGraw (1946) pointed out the existence of critical periods for the optimal learning of motor skills in human infants (Scott, 1962).

Example: Infant-Parent Attachment

The concept of critical or sensitive periods can also be found in the domain of social development, for example, in the formation of the infant-parent attachment relationship (Salkind, 2005).

Attachment describes the strong emotional ties between the infant and caregiver, a reciprocal relationship developing over the first year of the child’s life and particularly during the second six months of the first year.

During this attachment period , the infant’s social behavior becomes increasingly focused on the principal caregivers (Salkind, 2005).

The 20th-century English psychiatrist John Bowlby formulated and presented a comprehensive theory of attachment influenced by evolutionary theory.

Bowlby argued that the infant-parent attachment relationship develops because it is important to the survival of the infant and that the period from six to twenty-four months of age is a critical period of attachment.

This coincides with an infant’s increasing tendency to approach familiar caregivers and to be wary of unfamiliar adults. After this critical period, it is still possible for a first attachment relationship to develop, albeit with greater difficulty (Salkind, 2005).

This has brought into question, in a similar vein to language development, whether there is actually a critical development period for infant-caregiver attachment.

Sources debating this issue typically include cases of infants who did not experience consistent caregiving due to being raised in institutions prior to adoption (Salkind, 2005).

Early research into the critical period of attachment, published in the 1940s, reports consistently that children raised in orphanages subsequently showed unusual and maladaptive patterns of social behavior, difficulty in forming close relationships, and being indiscriminately friendly toward unfamiliar adults (Salkind, 2005).

Later, research from the 1990s indicated that adoptees were actually still able to form attachment relationships after the first year of life and also made developmental progress following adoption.

Nonetheless, these children had an overall increased risk of insecure or maladaptive attachment relationships with their adoptive parents. This evidence supports the notion of a sensitive period, but not a critical period, in the development of first attachment relationships (Salkind, 2005).

Mechanisms for Critical Periods

Both genetics and sensory experiences from outside the body shape the brain as it develops (Knudsen, 2004). However, the developmental stage that an organism is in significantly impacts how much the brain can change based on these experiences.

In scientific terms, the brain’s plasticity changes over the course of a lifespan. The brain is very plastic in the early stages of life before many key connections take root, but less so later.

This is why researchers have shown that early experience is crucial for the development of, say, language and musical abilities, and these skills are more challenging to take up in adulthood (Skoe and Kraus, 2013; White et al., 2013; Hartshorne et al., 2018).

As brains mature, the connections in them become more fixed. The brain’s transitions from a more plastic to a more fixed state advantageously allow it to retain new and complex processes, such as perceptual, motor, and cognitive functions (Piaget, 1962).

Children’s gestures, for example, pride and predict how they will acquire oral language skills (Colonnesi et al., 2010), which in turn are important for developing executive functions (Marcovitch and Zelazo, 2009).

However, this formation of stable connections in the brain can limit how the brain’s neural circuitry can be revised in the future. For example, if a young organism has abnormal sensory experiences during the critical period – such as auditory or visual deprivation – the brain may not wire itself in a way that processes future sensory inputs properly (Gallagher et al., 2020).

One illustration of this is the timing of cochlear implants – a prosthesis that restores hearing in some deaf people. Children who receive cochlear implants before two years of age are more likely to benefit from them than those who are implanted later in life (Kral and Eggermont, 2007; Gallagher et al., 2020).

Similarly, the visual deprivation caused by cataracts in infants can cause similar consequences. When cataracts are removed during early infancy, individuals can develop relatively normal vision; however, when the cataracts are not removed until adulthood, this results in substantially poorer vision (Martins Rosa et al., 2013).

After the critical period closes, abnormal sensory experiences have a less drastic effect on the brain and lead to – barring direct damage to the central nervous system – reversible changes (Gallagher et al., 2020). Much of what scientists know about critical periods derives from animal studies , as these allow researchers greater control over the variables that they are testing.

This research has found that different sensory systems, such as vision, auditory processing, and spatial hearing, have different critical periods (Gallagher et al., 2020).

The brain regulates when critical periods open and close by regulating how much the brain’s synapses take up neurotransmitters , which are chemical substances that affect the transmission of electrical signals between neurons.

In particular, over time, synapses decrease their uptake of gamma-aminobutyric acid, better known as GABA. At the beginning of the critical period, outside sources become more effective at influencing changes and growth in the brain.

Meanwhile, as the inhibitory circuits of the brain mature, the mature brain becomes less sensitive to sensory experiences (Gallagher et al., 2020).

Critical Periods vs Sensitive Periods

Critical periods are similar to sensitive periods, and scholars have, at times, used them interchangeably. However, they describe distinct but overlapping developmental processes.

A sensitive period is a developmental stage where sensory experiences have a greater impact on behavioral and brain development than usual; however, this influence is not exclusive to this time period (Knudsen, 2004; Gallagher, 2020). These sensitive periods are important for skills such as learning a language or instrument.

In contrast, A critical period is a special type of sensitive period – a window where sensory experience is necessary to shape the neural circuits involved in basic sensory processing, and when this window opens and closes is well-defined (Gallagher, 2020).

Researchers also refer to sensitive periods as weak critical periods. Some examples of strong critical periods include the development of vision and hearing, while weak critical periods include phenome tuning – how children learn how to organize sounds in a language, grammar processing, vocabulary acquisition, musical training, and sports training (Gallagher et al., 2020).

Critical Period Hypothesis

One of the most notable applications of the concept of a critical period is in linguistics. Scholars usually trace the origins of the debate around age in language acquisition to Penfield and Robert’s (2014) book Speech and Brain Mechanisms.

In the 1950s and 1960s, Penfield was a staunch advocate of early immersion education (Kroll and De Groot, 2009). Nonetheless, it was Lenneberg, in his book Biological Foundations of Language, who coined the term critical period (1967) in describing the language period.

Lennenberg (1967) described a critical period as a period of automatic acquisition from mere exposure” that “seems to disappear after this age.” Scovel (1969) later summarized and narrowed Penfield’s and Lenneberg’s view on the critical period hypothesis into three main claims:

  • Adult native speakers can identify non-natives by their accents immediately and accurately.
  • The loss of brain plasticity at about the age of puberty accounts for the emergence of foreign accents./li>
  • The critical period hypothesis only holds for speech (whether or not someone has a native accent) and does not affect other areas of linguistic competence.

Linguists have since attempted to find evidence for whether or not scientific evidence actually supports the critical period hypothesis, if there is a critical period for acquiring accentless speech, for “morphosyntactic” competence, and if these are true, how age-related differences can be explained on the neurological level (Scovel, 2000).

The critical period hypothesis applies to both first and second-language learning. Until recently, research around the critical period’s role in first language acquisition revolved around findings about so-called “feral” children who had failed to acquire language at an older age after having been deprived of normal input during the critical period.

However, these case studies did not account for the extent to which social deprivation, and possibly food deprivation or sensory deprivation, may have confounded with language input deprivation (Kroll and De Groot, 2009).

More recently, researchers have focused more systematically on deaf children born to hearing parents who are therefore deprived of language input until at least elementary school.

These studies have found the effects of lack of language input without extreme social deprivation: the older the age of exposure to sign language is, the worse its ultimate attainment (Emmorey, Bellugi, Friederici, and Horn, 1995; Kroll and De Groot, 2009).

However, Kroll and De Groot argue that the critical period hypothesis does not apply to the rate of acquisition of language. Adults and adolescents can learn languages at the same rate or even faster than children in their initial stage of acquisition (Slavoff and Johnson, 1995).

However, adults tend to have a more limited ultimate attainment of language ability (Kroll and De Groot, 2009).

There has been a long lineage of empirical findings around the age of acquisition. The most fundamental of this research comes from a series of studies since the late 1970s documenting a negative correlation between age of acquisition and ultimate language mastery (Kroll and De Grott, 2009).

Nonetheless, different periods correspond to sensitivity to different aspects of language. For example, shortly after birth, infants can perceive and discriminate speech sounds from any language, including ones they have not been exposed to (Eimas et al., 1971; Gallagher et al., 2020).

Around six months of age, exposure to the primary language in the infant’s environment guides phonetic representations of language and, subsequently, the neural representations of speech sounds of the native language while weakening those of unused sounds (McClelland et al., 1999; Gallagher et al., 2020).

Vocabulary learning experiences rapid growth at about 18 months of age (Kuhl, 2010).

Critical Evaluation

More than any other area of applied linguistics, the critical period hypothesis has impacted how teachers teach languages. Consequently, researchers have critiqued how important the critical period is to language learning.

For example, several studies in early language acquisition research showed that children were not necessarily superior to older learners in acquiring a second language, even in the area of pronunciation (Olson and Samuels, 1973; Snow and Hoefnagel-Hohle, 1978; Scovel, 2000).

In fact, the majority of researchers at the time appeared to be skeptical about the existence of a critical period, with some explicitly denying its existence.

Counter to one of the primary tenets of Scovel’s (1969) critical period hypothesis, there have been several cases of people who have acquired a second language in adulthood speaking with native accents.

For example, Moyer’s study of highly proficient English-speaking learners of German suggested that at least one of the participants was judged to have native-like pronunciation in his second language (1999), and several participants in Bongaerts (1999) study of highly proficient Dutch speakers of French spoke with accents judged to be native (Scovel, 2000).

Bongaerts, T. (1999). Ultimate attainment in L2 pronunciation: The case of very advanced late L2 learners. Second language acquisition and the critical period hypothesis, 133-159.

Cisneros-Franco, J. M., Voss, P., Thomas, M. E., & de Villers-Sidani, E. (2020). Critical periods of brain development. In Handbook of Clinical Neurolog y (Vol. 173, pp. 75-88). Elsevier.

Colonnesi, C., Stams, G. J. J., Koster, I., & Noom, M. J. (2010). The relation between pointing and language development: A meta-analysis. Developmental Review, 30 (4), 352-366.

Eimas, P. D., Siqueland, E. R., Jusczyk, P., & Vigorito, J. (1971). Speech perception in infants. Science, 171 (3968), 303-306.

Emmorey, K., Bellugi, U., Friederici, A., & Horn, P. (1995). Effects of age of acquisition on grammatical sensitivity: Evidence from on-line and off-line tasks. Applied Psycholinguistics, 16 (1), 1-23.

Knudsen, E. I. (2004). Sensitive periods in the development of the brain and behavior. Journal of cognitive neuroscience, 16 (8), 1412-1425.

Hartshorne, J. K., Tenenbaum, J. B., & Pinker, S. (2018). A critical period for second language acquisition: Evidence from 2/3 million English speakers. Cognition, 177 , 263-277.

Kral, A., & Eggermont, J. J. (2007). What’s to lose and what’s to learn: development under auditory deprivation, cochlear implants and limits of cortical plasticity. Brain Research Reviews, 56(1), 259-269.

Kroll, J. F., & De Groot, A. M. (Eds.). (2009). Handbook of bilingualism: Psycholinguistic approaches . Oxford University Press.

Kuhl, P. K. (2010). Brain mechanisms in early language acquisition. Neuron, 67 (5), 713-727.

Lenneberg, E. H. (1967). The biological foundations of language. Hospital Practice, 2( 12), 59-67.

Lorenz, K. (1935). Der kumpan in der umwelt des vogels. Journal für Ornithologie, 83 (2), 137-213.

Marcovitch, S., & Zelazo, P. D. (2009). A hierarchical competing systems model of the emergence and early development of executive function. Developmental science, 12 (1), 1-18.

McClelland, J. L., Thomas, A. G., McCandliss, B. D., & Fiez, J. A. (1999). Understanding failures of learning: Hebbian learning, competition for representational space, and some preliminary experimental data. Progress in brain research, 121, 75-80.

McGraw, M. B. (1946). Maturation of behavior. In Manual of child psychology. (pp. 332-369). John Wiley & Sons Inc.

Moyer, A. (1999). Ultimate attainment in L2 phonology: The critical factors of age, motivation, and instruction. Studies in second language acquisition, 21 (1), 81-108.

Gallagher, A., Bulteau, C., Cohen, D., & Michaud, J. L. (2019). Neurocognitive Development: Normative Development. Elsevier.

Olson, L. L., & Jay Samuels, S. (1973). The relationship between age and accuracy of foreign language pronunciation. The Journal of Educational Research, 66 (6), 263-268.

Penfield, W., & Roberts, L. (2014). Speech and brain mechanisms. Princeton University Press.

Piaget, J. (1962). The stages of the intellectual development of the child. Bulletin of the Menninger Clinic, 26 (3), 120.

Rosa, A. M., Silva, M. F., Ferreira, S., Murta, J., & Castelo-Branco, M. (2013). Plasticity in the human visual cortex: an ophthalmology-based perspective. BioMed research international, 2013.

Salkind, N. J. (Ed.). (2005). Encyclopedia of human development . Sage Publications.

Scott, J. P. (1962). Critical periods in behavioral development. Science, 138 (3544), 949-958.

Scovel, T. (1969). Foreign accents, language acquisition, and cerebral dominance 1. Language learning, 19 (3‐4), 245-253.

Scovel, T. (2000). A critical review of the critical period research. Annual review of applied linguistics, 20 , 213-223.

Skoe, E., & Kraus, N. (2013). Musical training heightens auditory brainstem function during sensitive periods in development. Frontiers in Psychology, 4, 622.

Slavoff, G. R., & Johnson, J. S. (1995). The effects of age on the rate of learning a second language. Studies in Second Language Acquisition, 17 (1), 1-16.

Snow, C. E., & Hoefnagel-Höhle, M. (1978). The critical period for language acquisition: Evidence from second language learning. Child development, 1114-1128.

Stockard, C. R. (1921). Developmental rate and structural expression: an experimental study of twins,‘double monsters’ and single deformities, and the interaction among embryonic organs during their origin and development. American Journal of Anatomy, 28 (2), 115-277.

White, E. J., Hutka, S. A., Williams, L. J., & Moreno, S. (2013). Learning, neural plasticity and sensitive periods: implications for language acquisition, music training and transfer across the lifespan. Frontiers in systems neuroscience, 7, 90.

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Please note you do not have access to teaching notes, the base-superstructure hypothesis and the foundations of critical theory.

Mediations of Social Life in the 21st Century

ISBN : 978-1-78441-223-4 , eISBN : 978-1-78441-222-7

Publication date: 31 October 2014

To defend the thesis that the base-superstructure hypothesis central to Marxist theory is also central paradigm of the tradition of Critical Theory. This is in opposition to those who see this hypothesis as determinist and eliminating the possibilities for the autonomy of social action. In doing so, it is able to retard and atrophy the critical capacities of subjects.

Design/methodology/approach

Emphasis on the return to a structural-functionalist understanding of social processes that places this version of Critical Theory against the more domesticated forms that consider “discourse ethics” and an “ethic of recognition” as the normative research program for Critical Theory. Also, an analysis of the purpose and logic of functional arguments and their relation to Marx’s concept of “determination” is undertaken.

The essence of Critical Theory hinges upon the ways that social structures are able to deform and shape structures of consciousness of modern subjects to predispose them to forms of domination and to view the prevailing hierarchical structures of extractive domination as legitimate in some basic sense.

Research limitations/implications

The foundations of Critical Theory need to be rooted in a renewed understanding of the relation between social structure and forms of consciousness. This means a move beyond theories of social practices into the realm of social epistemology as well as the mechanisms of consciousness and their relation to ideology.

Originality/value

Few analyses of the relation between the base and the superstructure or material organization of society and the social-epistemological layer of consciousness delineate the mechanisms involved in shaping consciousness. I undertake an analysis that utilizes insights from the philosophy of mind such as the theory of intentionality as well as the sociological approach to values through Parsons.

  • Critical Theory
  • Base and superstructure
  • Functionalism
  • Social epistemology

Acknowledgements

Acknowledgments.

Sections of an earlier draft of this paper were originally delivered at a conference on Critical Theory at New York University, April 28, 2013, and later at the 6th Annual Critical Theory Conference of Rome, Italy, May 6, 2013. I benefitted from discussions with Stephen Eric Bronner, Andrew Feenberg, Lauren Langman, and the comments of other participants at both venues.

Thompson, M.J. (2014), "The Base-Superstructure Hypothesis and the Foundations of Critical Theory", Mediations of Social Life in the 21st Century ( Current Perspectives in Social Theory, Vol. 32 ), Emerald Group Publishing Limited, Leeds, pp. 161-193. https://doi.org/10.1108/S0278-120420140000032007

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Research Article

The Critical Period Hypothesis in Second Language Acquisition: A Statistical Critique and a Reanalysis

* E-mail: [email protected]

Affiliation Department of Multilingualism, University of Fribourg, Fribourg, Switzerland

  • Jan Vanhove

PLOS

  • Published: July 25, 2013
  • https://doi.org/10.1371/journal.pone.0069172
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17 Jul 2014: The PLOS ONE Staff (2014) Correction: The Critical Period Hypothesis in Second Language Acquisition: A Statistical Critique and a Reanalysis. PLOS ONE 9(7): e102922. https://doi.org/10.1371/journal.pone.0102922 View correction

Figure 1

In second language acquisition research, the critical period hypothesis ( cph ) holds that the function between learners' age and their susceptibility to second language input is non-linear. This paper revisits the indistinctness found in the literature with regard to this hypothesis's scope and predictions. Even when its scope is clearly delineated and its predictions are spelt out, however, empirical studies–with few exceptions–use analytical (statistical) tools that are irrelevant with respect to the predictions made. This paper discusses statistical fallacies common in cph research and illustrates an alternative analytical method (piecewise regression) by means of a reanalysis of two datasets from a 2010 paper purporting to have found cross-linguistic evidence in favour of the cph . This reanalysis reveals that the specific age patterns predicted by the cph are not cross-linguistically robust. Applying the principle of parsimony, it is concluded that age patterns in second language acquisition are not governed by a critical period. To conclude, this paper highlights the role of confirmation bias in the scientific enterprise and appeals to second language acquisition researchers to reanalyse their old datasets using the methods discussed in this paper. The data and R commands that were used for the reanalysis are provided as supplementary materials.

Citation: Vanhove J (2013) The Critical Period Hypothesis in Second Language Acquisition: A Statistical Critique and a Reanalysis. PLoS ONE 8(7): e69172. https://doi.org/10.1371/journal.pone.0069172

Editor: Stephanie Ann White, UCLA, United States of America

Received: May 7, 2013; Accepted: June 7, 2013; Published: July 25, 2013

Copyright: © 2013 Jan Vanhove. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: No current external funding sources for this study.

Competing interests: The author has declared that no competing interests exist.

Introduction

In the long term and in immersion contexts, second-language (L2) learners starting acquisition early in life – and staying exposed to input and thus learning over several years or decades – undisputedly tend to outperform later learners. Apart from being misinterpreted as an argument in favour of early foreign language instruction, which takes place in wholly different circumstances, this general age effect is also sometimes taken as evidence for a so-called ‘critical period’ ( cp ) for second-language acquisition ( sla ). Derived from biology, the cp concept was famously introduced into the field of language acquisition by Penfield and Roberts in 1959 [1] and was refined by Lenneberg eight years later [2] . Lenneberg argued that language acquisition needed to take place between age two and puberty – a period which he believed to coincide with the lateralisation process of the brain. (More recent neurological research suggests that different time frames exist for the lateralisation process of different language functions. Most, however, close before puberty [3] .) However, Lenneberg mostly drew on findings pertaining to first language development in deaf children, feral children or children with serious cognitive impairments in order to back up his claims. For him, the critical period concept was concerned with the implicit “automatic acquisition” [2, p. 176] in immersion contexts and does not preclude the possibility of learning a foreign language after puberty, albeit with much conscious effort and typically less success.

sla research adopted the critical period hypothesis ( cph ) and applied it to second and foreign language learning, resulting in a host of studies. In its most general version, the cph for sla states that the ‘susceptibility’ or ‘sensitivity’ to language input varies as a function of age, with adult L2 learners being less susceptible to input than child L2 learners. Importantly, the age–susceptibility function is hypothesised to be non-linear. Moving beyond this general version, we find that the cph is conceptualised in a multitude of ways [4] . This state of affairs requires scholars to make explicit their theoretical stance and assumptions [5] , but has the obvious downside that critical findings risk being mitigated as posing a problem to only one aspect of one particular conceptualisation of the cph , whereas other conceptualisations remain unscathed. This overall vagueness concerns two areas in particular, viz. the delineation of the cph 's scope and the formulation of testable predictions. Delineating the scope and formulating falsifiable predictions are, needless to say, fundamental stages in the scientific evaluation of any hypothesis or theory, but the lack of scholarly consensus on these points seems to be particularly pronounced in the case of the cph . This article therefore first presents a brief overview of differing views on these two stages. Then, once the scope of their cph version has been duly identified and empirical data have been collected using solid methods, it is essential that researchers analyse the data patterns soundly in order to assess the predictions made and that they draw justifiable conclusions from the results. As I will argue in great detail, however, the statistical analysis of data patterns as well as their interpretation in cph research – and this includes both critical and supportive studies and overviews – leaves a great deal to be desired. Reanalysing data from a recent cph -supportive study, I illustrate some common statistical fallacies in cph research and demonstrate how one particular cph prediction can be evaluated.

Delineating the scope of the critical period hypothesis

First, the age span for a putative critical period for language acquisition has been delimited in different ways in the literature [4] . Lenneberg's critical period stretched from two years of age to puberty (which he posits at about 14 years of age) [2] , whereas other scholars have drawn the cutoff point at 12, 15, 16 or 18 years of age [6] . Unlike Lenneberg, most researchers today do not define a starting age for the critical period for language learning. Some, however, consider the possibility of the critical period (or a critical period for a specific language area, e.g. phonology) ending much earlier than puberty (e.g. age 9 years [1] , or as early as 12 months in the case of phonology [7] ).

Second, some vagueness remains as to the setting that is relevant to the cph . Does the critical period constrain implicit learning processes only, i.e. only the untutored language acquisition in immersion contexts or does it also apply to (at least partly) instructed learning? Most researchers agree on the former [8] , but much research has included subjects who have had at least some instruction in the L2.

Third, there is no consensus on what the scope of the cp is as far as the areas of language that are concerned. Most researchers agree that a cp is most likely to constrain the acquisition of pronunciation and grammar and, consequently, these are the areas primarily looked into in studies on the cph [9] . Some researchers have also tried to define distinguishable cp s for the different language areas of phonetics, morphology and syntax and even for lexis (see [10] for an overview).

Fourth and last, research into the cph has focused on ‘ultimate attainment’ ( ua ) or the ‘final’ state of L2 proficiency rather than on the rate of learning. From research into the rate of acquisition (e.g. [11] – [13] ), it has become clear that the cph cannot hold for the rate variable. In fact, it has been observed that adult learners proceed faster than child learners at the beginning stages of L2 acquisition. Though theoretical reasons for excluding the rate can be posited (the initial faster rate of learning in adults may be the result of more conscious cognitive strategies rather than to less conscious implicit learning, for instance), rate of learning might from a different perspective also be considered an indicator of ‘susceptibility’ or ‘sensitivity’ to language input. Nevertheless, contemporary sla scholars generally seem to concur that ua and not rate of learning is the dependent variable of primary interest in cph research. These and further scope delineation problems relevant to cph research are discussed in more detail by, among others, Birdsong [9] , DeKeyser and Larson-Hall [14] , Long [10] and Muñoz and Singleton [6] .

Formulating testable hypotheses

Once the relevant cph 's scope has satisfactorily been identified, clear and testable predictions need to be drawn from it. At this stage, the lack of consensus on what the consequences or the actual observable outcome of a cp would have to look like becomes evident. As touched upon earlier, cph research is interested in the end state or ‘ultimate attainment’ ( ua ) in L2 acquisition because this “determines the upper limits of L2 attainment” [9, p. 10]. The range of possible ultimate attainment states thus helps researchers to explore the potential maximum outcome of L2 proficiency before and after the putative critical period.

One strong prediction made by some cph exponents holds that post- cp learners cannot reach native-like L2 competences. Identifying a single native-like post- cp L2 learner would then suffice to falsify all cph s making this prediction. Assessing this prediction is difficult, however, since it is not clear what exactly constitutes sufficient nativelikeness, as illustrated by the discussion on the actual nativelikeness of highly accomplished L2 speakers [15] , [16] . Indeed, there exists a real danger that, in a quest to vindicate the cph , scholars set the bar for L2 learners to match monolinguals increasingly higher – up to Swiftian extremes. Furthermore, the usefulness of comparing the linguistic performance in mono- and bilinguals has been called into question [6] , [17] , [18] . Put simply, the linguistic repertoires of mono- and bilinguals differ by definition and differences in the behavioural outcome will necessarily be found, if only one digs deep enough.

A second strong prediction made by cph proponents is that the function linking age of acquisition and ultimate attainment will not be linear throughout the whole lifespan. Before discussing how this function would have to look like in order for it to constitute cph -consistent evidence, I point out that the ultimate attainment variable can essentially be considered a cumulative measure dependent on the actual variable of interest in cph research, i.e. susceptibility to language input, as well as on such other factors like duration and intensity of learning (within and outside a putative cp ) and possibly a number of other influencing factors. To elaborate, the behavioural outcome, i.e. ultimate attainment, can be assumed to be integrative to the susceptibility function, as Newport [19] correctly points out. Other things being equal, ultimate attainment will therefore decrease as susceptibility decreases. However, decreasing ultimate attainment levels in and by themselves represent no compelling evidence in favour of a cph . The form of the integrative curve must therefore be predicted clearly from the susceptibility function. Additionally, the age of acquisition–ultimate attainment function can take just about any form when other things are not equal, e.g. duration of learning (Does learning last up until time of testing or only for a more or less constant number of years or is it dependent on age itself?) or intensity of learning (Do learners always learn at their maximum susceptibility level or does this intensity vary as a function of age, duration, present attainment and motivation?). The integral of the susceptibility function could therefore be of virtually unlimited complexity and its parameters could be adjusted to fit any age of acquisition–ultimate attainment pattern. It seems therefore astonishing that the distinction between level of sensitivity to language input and level of ultimate attainment is rarely made in the literature. Implicitly or explicitly [20] , the two are more or less equated and the same mathematical functions are expected to describe the two variables if observed across a range of starting ages of acquisition.

But even when the susceptibility and ultimate attainment variables are equated, there remains controversy as to what function linking age of onset of acquisition and ultimate attainment would actually constitute evidence for a critical period. Most scholars agree that not any kind of age effect constitutes such evidence. More specifically, the age of acquisition–ultimate attainment function would need to be different before and after the end of the cp [9] . According to Birdsong [9] , three basic possible patterns proposed in the literature meet this condition. These patterns are presented in Figure 1 . The first pattern describes a steep decline of the age of onset of acquisition ( aoa )–ultimate attainment ( ua ) function up to the end of the cp and a practically non-existent age effect thereafter. Pattern 2 is an “unconventional, although often implicitly invoked” [9, p. 17] notion of the cp function which contains a period of peak attainment (or performance at ceiling), i.e. performance does not vary as a function of age, which is often referred to as a ‘window of opportunity’. This time span is followed by an unbounded decline in ua depending on aoa . Pattern 3 includes characteristics of patterns 1 and 2. At the beginning of the aoa range, performance is at ceiling. The next segment is a downward slope in the age function which ends when performance reaches its floor. Birdsong points out that all of these patterns have been reported in the literature. On closer inspection, however, he concludes that the most convincing function describing these age effects is a simple linear one. Hakuta et al. [21] sketch further theoretically possible predictions of the cph in which the mean performance drops drastically and/or the slope of the aoa – ua proficiency function changes at a certain point.

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The graphs are based on based on Figure 2 in [9] .

https://doi.org/10.1371/journal.pone.0069172.g001

Although several patterns have been proposed in the literature, it bears pointing out that the most common explicit prediction corresponds to Birdsong's first pattern, as exemplified by the following crystal-clear statement by DeKeyser, one of the foremost cph proponents:

[A] strong negative correlation between age of acquisition and ultimate attainment throughout the lifespan (or even from birth through middle age), the only age effect documented in many earlier studies, is not evidence for a critical period…[T]he critical period concept implies a break in the AoA–proficiency function, i.e., an age (somewhat variable from individual to individual, of course, and therefore an age range in the aggregate) after which the decline of success rate in one or more areas of language is much less pronounced and/or clearly due to different reasons. [22, p. 445].

DeKeyser and before him among others Johnson and Newport [23] thus conceptualise only one possible pattern which would speak in favour of a critical period: a clear negative age effect before the end of the critical period and a much weaker (if any) negative correlation between age and ultimate attainment after it. This ‘flattened slope’ prediction has the virtue of being much more tangible than the ‘potential nativelikeness’ prediction: Testing it does not necessarily require comparing the L2-learners to a native control group and thus effectively comparing apples and oranges. Rather, L2-learners with different aoa s can be compared amongst themselves without the need to categorise them by means of a native-speaker yardstick, the validity of which is inevitably going to be controversial [15] . In what follows, I will concern myself solely with the ‘flattened slope’ prediction, arguing that, despite its clarity of formulation, cph research has generally used analytical methods that are irrelevant for the purposes of actually testing it.

Inferring non-linearities in critical period research: An overview

critical theory hypothesis

Group mean or proportion comparisons.

critical theory hypothesis

[T]he main differences can be found between the native group and all other groups – including the earliest learner group – and between the adolescence group and all other groups. However, neither the difference between the two childhood groups nor the one between the two adulthood groups reached significance, which indicates that the major changes in eventual perceived nativelikeness of L2 learners can be associated with adolescence. [15, p. 270].

Similar group comparisons aimed at investigating the effect of aoa on ua have been carried out by both cph advocates and sceptics (among whom Bialystok and Miller [25, pp. 136–139], Birdsong and Molis [26, p. 240], Flege [27, pp. 120–121], Flege et al. [28, pp. 85–86], Johnson [29, p. 229], Johnson and Newport [23, p. 78], McDonald [30, pp. 408–410] and Patowski [31, pp. 456–458]). To be clear, not all of these authors drew direct conclusions about the aoa – ua function on the basis of these groups comparisons, but their group comparisons have been cited as indicative of a cph -consistent non-continuous age effect, as exemplified by the following quote by DeKeyser [22] :

Where group comparisons are made, younger learners always do significantly better than the older learners. The behavioral evidence, then, suggests a non-continuous age effect with a “bend” in the AoA–proficiency function somewhere between ages 12 and 16. [22, p. 448].

The first problem with group comparisons like these and drawing inferences on the basis thereof is that they require that a continuous variable, aoa , be split up into discrete bins. More often than not, the boundaries between these bins are drawn in an arbitrary fashion, but what is more troublesome is the loss of information and statistical power that such discretisation entails (see [32] for the extreme case of dichotomisation). If we want to find out more about the relationship between aoa and ua , why throw away most of the aoa information and effectively reduce the ua data to group means and the variance in those groups?

critical theory hypothesis

Comparison of correlation coefficients.

critical theory hypothesis

Correlation-based inferences about slope discontinuities have similarly explicitly been made by cph advocates and skeptics alike, e.g. Bialystok and Miller [25, pp. 136 and 140], DeKeyser and colleagues [22] , [44] and Flege et al. [45, pp. 166 and 169]. Others did not explicitly infer the presence or absence of slope differences from the subset correlations they computed (among others Birdsong and Molis [26] , DeKeyser [8] , Flege et al. [28] and Johnson [29] ), but their studies nevertheless featured in overviews discussing discontinuities [14] , [22] . Indeed, the most recent overview draws a strong conclusion about the validity of the cph 's ‘flattened slope’ prediction on the basis of these subset correlations:

In those studies where the two groups are described separately, the correlation is much higher for the younger than for the older group, except in Birdsong and Molis (2001) [ =  [26] , JV], where there was a ceiling effect for the younger group. This global picture from more than a dozen studies provides support for the non-continuity of the decline in the AoA–proficiency function, which all researchers agree is a hallmark of a critical period phenomenon. [22, p. 448].

In Johnson and Newport's specific case [23] , their correlation-based inference that ua levels off after puberty happened to be largely correct: the gjt scores are more or less randomly distributed around a near-horizontal trend line [26] . Ultimately, however, it rests on the fallacy of confusing correlation coefficients with slopes, which seriously calls into question conclusions such as DeKeyser's (cf. the quote above).

critical theory hypothesis

https://doi.org/10.1371/journal.pone.0069172.g002

critical theory hypothesis

Lower correlation coefficients in older aoa groups may therefore be largely due to differences in ua variance, which have been reported in several studies [23] , [26] , [28] , [29] (see [46] for additional references). Greater variability in ua with increasing age is likely due to factors other than age proper [47] , such as the concomitant greater variability in exposure to literacy, degree of education, motivation and opportunity for language use, and by itself represents evidence neither in favour of nor against the cph .

Regression approaches.

Having demonstrated that neither group mean or proportion comparisons nor correlation coefficient comparisons can directly address the ‘flattened slope’ prediction, I now turn to the studies in which regression models were computed with aoa as a predictor variable and ua as the outcome variable. Once again, this category of studies is not mutually exclusive with the two categories discussed above.

In a large-scale study using self-reports and approximate aoa s derived from a sample of the 1990 U.S. Census, Stevens found that the probability with which immigrants from various countries stated that they spoke English ‘very well’ decreased curvilinearly as a function of aoa [48] . She noted that this development is similar to the pattern found by Johnson and Newport [23] but that it contains no indication of an “abruptly defined ‘critical’ or sensitive period in L2 learning” [48, p. 569]. However, she modelled the self-ratings using an ordinal logistic regression model in which the aoa variable was logarithmically transformed. Technically, this is perfectly fine, but one should be careful not to read too much into the non-linear curves found. In logistic models, the outcome variable itself is modelled linearly as a function of the predictor variables and is expressed in log-odds. In order to compute the corresponding probabilities, these log-odds are transformed using the logistic function. Consequently, even if the model is specified linearly, the predicted probabilities will not lie on a perfectly straight line when plotted as a function of any one continuous predictor variable. Similarly, when the predictor variable is first logarithmically transformed and then used to linearly predict an outcome variable, the function linking the predicted outcome variables and the untransformed predictor variable is necessarily non-linear. Thus, non-linearities follow naturally from Stevens's model specifications. Moreover, cph -consistent discontinuities in the aoa – ua function cannot be found using her model specifications as they did not contain any parameters allowing for this.

Using data similar to Stevens's, Bialystok and Hakuta found that the link between the self-rated English competences of Chinese- and Spanish-speaking immigrants and their aoa could be described by a straight line [49] . In contrast to Stevens, Bialystok and Hakuta used a regression-based method allowing for changes in the function's slope, viz. locally weighted scatterplot smoothing ( lowess ). Informally, lowess is a non-parametrical method that relies on an algorithm that fits the dependent variable for small parts of the range of the independent variable whilst guaranteeing that the overall curve does not contain sudden jumps (for technical details, see [50] ). Hakuta et al. used an even larger sample from the same 1990 U.S. Census data on Chinese- and Spanish-speaking immigrants (2.3 million observations) [21] . Fitting lowess curves, no discontinuities in the aoa – ua slope could be detected. Moreover, the authors found that piecewise linear regression models, i.e. regression models containing a parameter that allows a sudden drop in the curve or a change of its slope, did not provide a better fit to the data than did an ordinary regression model without such a parameter.

critical theory hypothesis

To sum up, I have argued at length that regression approaches are superior to group mean and correlation coefficient comparisons for the purposes of testing the ‘flattened slope’ prediction. Acknowledging the reservations vis-à-vis self-estimated ua s, we still find that while the relationship between aoa and ua is not necessarily perfectly linear in the studies discussed, the data do not lend unequivocal support to this prediction. In the following section, I will reanalyse data from a recent empirical paper on the cph by DeKeyser et al. [44] . The first goal of this reanalysis is to further illustrate some of the statistical fallacies encountered in cph studies. Second, by making the computer code available I hope to demonstrate how the relevant regression models, viz. piecewise regression models, can be fitted and how the aoa representing the optimal breakpoint can be identified. Lastly, the findings of this reanalysis will contribute to our understanding of how aoa affects ua as measured using a gjt .

Summary of DeKeyser et al. (2010)

I chose to reanalyse a recent empirical paper on the cph by DeKeyser et al. [44] (henceforth DK et al.). This paper lends itself well to a reanalysis since it exhibits two highly commendable qualities: the authors spell out their hypotheses lucidly and provide detailed numerical and graphical data descriptions. Moreover, the paper's lead author is very clear on what constitutes a necessary condition for accepting the cph : a non-linearity in the age of onset of acquisition ( aoa )–ultimate attainment ( ua ) function, with ua declining less strongly as a function of aoa in older, post- cp arrivals compared to younger arrivals [14] , [22] . Lastly, it claims to have found cross-linguistic evidence from two parallel studies backing the cph and should therefore be an unsuspected source to cph proponents.

critical theory hypothesis

The authors set out to test the following hypotheses:

  • Hypothesis 1: For both the L2 English and the L2 Hebrew group, the slope of the age of arrival–ultimate attainment function will not be linear throughout the lifespan, but will instead show a marked flattening between adolescence and adulthood.
  • Hypothesis 2: The relationship between aptitude and ultimate attainment will differ markedly for the young and older arrivals, with significance only for the latter. (DK et al., p. 417)

Both hypotheses were purportedly confirmed, which in the authors' view provides evidence in favour of cph . The problem with this conclusion, however, is that it is based on a comparison of correlation coefficients. As I have argued above, correlation coefficients are not to be confused with regression coefficients and cannot be used to directly address research hypotheses concerning slopes, such as Hypothesis 1. In what follows, I will reanalyse the relationship between DK et al.'s aoa and gjt data in order to address Hypothesis 1. Additionally, I will lay bare a problem with the way in which Hypothesis 2 was addressed. The extracted data and the computer code used for the reanalysis are provided as supplementary materials, allowing anyone interested to scrutinise and easily reproduce my whole analysis and carry out their own computations (see ‘supporting information’).

Data extraction

critical theory hypothesis

In order to verify whether we did in fact extract the data points to a satisfactory degree of accuracy, I computed summary statistics for the extracted aoa and gjt data and checked these against the descriptive statistics provided by DK et al. (pp. 421 and 427). These summary statistics for the extracted data are presented in Table 1 . In addition, I computed the correlation coefficients for the aoa – gjt relationship for the whole aoa range and for aoa -defined subgroups and checked these coefficients against those reported by DK et al. (pp. 423 and 428). The correlation coefficients computed using the extracted data are presented in Table 2 . Both checks strongly suggest the extracted data to be virtually identical to the original data, and Dr DeKeyser confirmed this to be the case in response to an earlier draft of the present paper (personal communication, 6 May 2013).

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https://doi.org/10.1371/journal.pone.0069172.t001

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https://doi.org/10.1371/journal.pone.0069172.t002

Results and Discussion

Modelling the link between age of onset of acquisition and ultimate attainment.

I first replotted the aoa and gjt data we extracted from DK et al.'s scatterplots and added non-parametric scatterplot smoothers in order to investigate whether any changes in slope in the aoa – gjt function could be revealed, as per Hypothesis 1. Figures 3 and 4 show this not to be the case. Indeed, simple linear regression models that model gjt as a function of aoa provide decent fits for both the North America and the Israel data, explaining 65% and 63% of the variance in gjt scores, respectively. The parameters of these models are given in Table 3 .

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The trend line is a non-parametric scatterplot smoother. The scatterplot itself is a near-perfect replication of DK et al.'s Fig. 1.

https://doi.org/10.1371/journal.pone.0069172.g003

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The trend line is a non-parametric scatterplot smoother. The scatterplot itself is a near-perfect replication of DK et al.'s Fig. 5.

https://doi.org/10.1371/journal.pone.0069172.g004

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https://doi.org/10.1371/journal.pone.0069172.t003

critical theory hypothesis

To ensure that both segments are joined at the breakpoint, the predictor variable is first centred at the breakpoint value, i.e. the breakpoint value is subtracted from the original predictor variable values. For a blow-by-blow account of how such models can be fitted in r , I refer to an example analysis by Baayen [55, pp. 214–222].

critical theory hypothesis

Solid: regression with breakpoint at aoa 18 (dashed lines represent its 95% confidence interval); dot-dash: regression without breakpoint.

https://doi.org/10.1371/journal.pone.0069172.g005

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Solid: regression with breakpoint at aoa 18 (dashed lines represent its 95% confidence interval); dot-dash (hardly visible due to near-complete overlap): regression without breakpoint.

https://doi.org/10.1371/journal.pone.0069172.g006

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https://doi.org/10.1371/journal.pone.0069172.t004

critical theory hypothesis

https://doi.org/10.1371/journal.pone.0069172.g007

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Solid: regression with breakpoint at aoa 16 (dashed lines represent its 95% confidence interval); dot-dash: regression without breakpoint.

https://doi.org/10.1371/journal.pone.0069172.g008

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Solid: regression with breakpoint at aoa 6 (dashed lines represent its 95% confidence interval); dot-dash (hardly visible due to near-complete overlap): regression without breakpoint.

https://doi.org/10.1371/journal.pone.0069172.g009

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https://doi.org/10.1371/journal.pone.0069172.t005

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https://doi.org/10.1371/journal.pone.0069172.t006

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https://doi.org/10.1371/journal.pone.0069172.t007

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https://doi.org/10.1371/journal.pone.0069172.t008

critical theory hypothesis

In sum, a regression model that allows for changes in the slope of the the aoa – gjt function to account for putative critical period effects provides a somewhat better fit to the North American data than does an everyday simple regression model. The improvement in model fit is marginal, however, and including a breakpoint does not result in any detectable improvement of model fit to the Israel data whatsoever. Breakpoint models therefore fail to provide solid cross-linguistic support in favour of critical period effects: across both data sets, gjt can satisfactorily be modelled as a linear function of aoa .

On partialling out ‘age at testing’

As I have argued above, correlation coefficients cannot be used to test hypotheses about slopes. When the correct procedure is carried out on DK et al.'s data, no cross-linguistically robust evidence for changes in the aoa – gjt function was found. In addition to comparing the zero-order correlations between aoa and gjt , however, DK et al. computed partial correlations in which the variance in aoa associated with the participants' age at testing ( aat ; a potentially confounding variable) was filtered out. They found that these partial correlations between aoa and gjt , which are given in Table 9 , differed between age groups in that they are stronger for younger than for older participants. This, DK et al. argue, constitutes additional evidence in favour of the cph . At this point, I can no longer provide my own analysis of DK et al.'s data seeing as the pertinent data points were not plotted. Nevertheless, the detailed descriptions by DK et al. strongly suggest that the use of these partial correlations is highly problematic. Most importantly, and to reiterate, correlations (whether zero-order or partial ones) are actually of no use when testing hypotheses concerning slopes. Still, one may wonder why the partial correlations differ across age groups. My surmise is that these differences are at least partly the by-product of an imbalance in the sampling procedure.

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https://doi.org/10.1371/journal.pone.0069172.t009

critical theory hypothesis

The upshot of this brief discussion is that the partial correlation differences reported by DK et al. are at least partly the result of an imbalance in the sampling procedure: aoa and aat were simply less intimately tied for the young arrivals in the North America study than for the older arrivals with L2 English or for all of the L2 Hebrew participants. In an ideal world, we would like to fix aat or ascertain that it at most only weakly correlates with aoa . This, however, would result in a strong correlation between aoa and another potential confound variable, length of residence in the L2 environment, bringing us back to square one. Allowing for only moderate correlations between aoa and aat might improve our predicament somewhat, but even in that case, we should tread lightly when making inferences on the basis of statistical control procedures [61] .

On estimating the role of aptitude

Having shown that Hypothesis 1 could not be confirmed, I now turn to Hypothesis 2, which predicts a differential role of aptitude for ua in sla in different aoa groups. More specifically, it states that the correlation between aptitude and gjt performance will be significant only for older arrivals. The correlation coefficients of the relationship between aptitude and gjt are presented in Table 10 .

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https://doi.org/10.1371/journal.pone.0069172.t010

The problem with both the wording of Hypothesis 2 and the way in which it is addressed is the following: it is assumed that a variable has a reliably different effect in different groups when the effect reaches significance in one group but not in the other. This logic is fairly widespread within several scientific disciplines (see e.g. [62] for a discussion). Nonetheless, it is demonstrably fallacious [63] . Here we will illustrate the fallacy for the specific case of comparing two correlation coefficients.

critical theory hypothesis

Apart from not being replicated in the North America study, does this difference actually show anything? I contend that it does not: what is of interest are not so much the correlation coefficients, but rather the interactions between aoa and aptitude in models predicting gjt . These interactions could be investigated by fitting a multiple regression model in which the postulated cp breakpoint governs the slope of both aoa and aptitude. If such a model provided a substantially better fit to the data than a model without a breakpoint for the aptitude slope and if the aptitude slope changes in the expected direction (i.e. a steeper slope for post- cp than for younger arrivals) for different L1–L2 pairings, only then would this particular prediction of the cph be borne out.

Using data extracted from a paper reporting on two recent studies that purport to provide evidence in favour of the cph and that, according to its authors, represent a major improvement over earlier studies (DK et al., p. 417), it was found that neither of its two hypotheses were actually confirmed when using the proper statistical tools. As a matter of fact, the gjt scores continue to decline at essentially the same rate even beyond the end of the putative critical period. According to the paper's lead author, such a finding represents a serious problem to his conceptualisation of the cph [14] ). Moreover, although modelling a breakpoint representing the end of a cp at aoa 16 may improve the statistical model slightly in study on learners of English in North America, the study on learners of Hebrew in Israel fails to confirm this finding. In fact, even if we were to accept the optimal breakpoint computed for the Israel study, it lies at aoa 6 and is associated with a different geometrical pattern.

Diverging age trends in parallel studies with participants with different L2s have similarly been reported by Birdsong and Molis [26] and are at odds with an L2-independent cph . One parsimonious explanation of such conflicting age trends may be that the overall, cross-linguistic age trend is in fact linear, but that fluctuations in the data (due to factors unaccounted for or randomness) may sometimes give rise to a ‘stretched L’-shaped pattern ( Figure 1, left panel ) and sometimes to a ‘stretched 7’-shaped pattern ( Figure 1 , middle panel; see also [66] for a similar comment).

Importantly, the criticism that DeKeyser and Larsson-Hall levy against two studies reporting findings similar to the present [48] , [49] , viz. that the data consisted of self-ratings of questionable validity [14] , does not apply to the present data set. In addition, DK et al. did not exclude any outliers from their analyses, so I assume that DeKeyser and Larsson-Hall's criticism [14] of Birdsong and Molis's study [26] , i.e. that the findings were due to the influence of outliers, is not applicable to the present data either. For good measure, however, I refitted the regression models with and without breakpoints after excluding one potentially problematic data point per model. The following data points had absolute standardised residuals larger than 2.5 in the original models without breakpoints as well as in those with breakpoints: the participant with aoa 17 and a gjt score of 125 in the North America study and the participant with aoa 12 and a gjt score of 117 in the Israel study. The resultant models were virtually identical to the original models (see Script S1 ). Furthermore, the aoa variable was sufficiently fine-grained and the aoa – gjt curve was not ‘presmoothed’ by the prior aggregation of gjt across parts of the aoa range (see [51] for such a criticism of another study). Lastly, seven of the nine “problems with supposed counter-evidence” to the cph discussed by Long [5] do not apply either, viz. (1) “[c]onfusion of rate and ultimate attainment”, (2) “[i]nappropriate choice of subjects”, (3) “[m]easurement of AO”, (4) “[l]eading instructions to raters”, (6) “[u]se of markedly non-native samples making near-native samples more likely to sound native to raters”, (7) “[u]nreliable or invalid measures”, and (8) “[i]nappropriate L1–L2 pairings”. Problem No. 5 (“Assessments based on limited samples and/or “language-like” behavior”) may be apropos given that only gjt data were used, leaving open the theoretical possibility that other measures might have yielded a different outcome. Finally, problem No. 9 (“Faulty interpretation of statistical patterns”) is, of course, precisely what I have turned the spotlights on.

Conclusions

The critical period hypothesis remains a hotly contested issue in the psycholinguistics of second-language acquisition. Discussions about the impact of empirical findings on the tenability of the cph generally revolve around the reliability of the data gathered (e.g. [5] , [14] , [22] , [52] , [67] , [68] ) and such methodological critiques are of course highly desirable. Furthermore, the debate often centres on the question of exactly what version of the cph is being vindicated or debunked. These versions differ mainly in terms of its scope, specifically with regard to the relevant age span, setting and language area, and the testable predictions they make. But even when the cph 's scope is clearly demarcated and its main prediction is spelt out lucidly, the issue remains to what extent the empirical findings can actually be marshalled in support of the relevant cph version. As I have shown in this paper, empirical data have often been taken to support cph versions predicting that the relationship between age of acquisition and ultimate attainment is not strictly linear, even though the statistical tools most commonly used (notably group mean and correlation coefficient comparisons) were, crudely put, irrelevant to this prediction. Methods that are arguably valid, e.g. piecewise regression and scatterplot smoothing, have been used in some studies [21] , [26] , [49] , but these studies have been criticised on other grounds. To my knowledge, such methods have never been used by scholars who explicitly subscribe to the cph .

I suspect that what may be going on is a form of ‘confirmation bias’ [69] , a cognitive bias at play in diverse branches of human knowledge seeking: Findings judged to be consistent with one's own hypothesis are hardly questioned, whereas findings inconsistent with one's own hypothesis are scrutinised much more strongly and criticised on all sorts of points [70] – [73] . My reanalysis of DK et al.'s recent paper may be a case in point. cph exponents used correlation coefficients to address their prediction about the slope of a function, as had been done in a host of earlier studies. Finding a result that squared with their expectations, they did not question the technical validity of their results, or at least they did not report this. (In fact, my reanalysis is actually a case in point in two respects: for an earlier draft of this paper, I had computed the optimal position of the breakpoints incorrectly, resulting in an insignificant improvement of model fit for the North American data rather than a borderline significant one. Finding a result that squared with my expectations, I did not question the technical validity of my results – until this error was kindly pointed out to me by Martijn Wieling (University of Tübingen).) That said, I am keen to point out that the statistical analyses in this particular paper, though suboptimal, are, as far as I could gather, reported correctly, i.e. the confirmation bias does not seem to have resulted in the blatant misreportings found elsewhere (see [74] for empirical evidence and discussion). An additional point to these authors' credit is that, apart from explicitly identifying their cph version's scope and making crystal-clear predictions, they present data descriptions that actually permit quantitative reassessments and have a history of doing so (e.g. the appendix in [8] ). This leads me to believe that they analysed their data all in good conscience and to hope that they, too, will conclude that their own data do not, in fact, support their hypothesis.

I end this paper on an upbeat note. Even though I have argued that the analytical tools employed in cph research generally leave much to be desired, the original data are, so I hope, still available. This provides researchers, cph supporters and sceptics alike, with an exciting opportunity to reanalyse their data sets using the tools outlined in the present paper and publish their findings at minimal cost of time and resources (for instance, as a comment to this paper). I would therefore encourage scholars to engage their old data sets and to communicate their analyses openly, e.g. by voluntarily publishing their data and computer code alongside their articles or comments. Ideally, cph supporters and sceptics would join forces to agree on a protocol for a high-powered study in order to provide a truly convincing answer to a core issue in sla .

Supporting Information

Dataset s1..

aoa and gjt data extracted from DeKeyser et al.'s North America study.

https://doi.org/10.1371/journal.pone.0069172.s001

Dataset S2.

aoa and gjt data extracted from DeKeyser et al.'s Israel study.

https://doi.org/10.1371/journal.pone.0069172.s002

Script with annotated R code used for the reanalysis. All add-on packages used can be installed from within R.

https://doi.org/10.1371/journal.pone.0069172.s003

Acknowledgments

I would like to thank Irmtraud Kaiser (University of Fribourg) for helping me to get an overview of the literature on the critical period hypothesis in second language acquisition. Thanks are also due to Martijn Wieling (currently University of Tübingen) for pointing out an error in the R code accompanying an earlier draft of this paper.

Author Contributions

Analyzed the data: JV. Wrote the paper: JV.

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Age and the critical period hypothesis

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Christian Abello-Contesse, Age and the critical period hypothesis, ELT Journal , Volume 63, Issue 2, April 2009, Pages 170–172, https://doi.org/10.1093/elt/ccn072

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In the field of second language acquisition (SLA), how specific aspects of learning a non-native language (L2) may be affected by when the process begins is referred to as the ‘age factor’. Because of the way age intersects with a range of social, affective, educational, and experiential variables, clarifying its relationship with learning rate and/or success is a major challenge.

There is a popular belief that children as L2 learners are ‘superior’ to adults ( Scovel 2000 ), that is, the younger the learner, the quicker the learning process and the better the outcomes. Nevertheless, a closer examination of the ways in which age combines with other variables reveals a more complex picture, with both favourable and unfavourable age-related differences being associated with early- and late-starting L2 learners ( Johnstone 2002 ).

The ‘critical period hypothesis’ (CPH) is a particularly relevant case in point. This is the claim that there is, indeed, an optimal period for language acquisition, ending at puberty. However, in its original formulation ( Lenneberg 1967 ), evidence for its existence was based on the relearning of impaired L1 skills, rather than the learning of a second language under normal circumstances.

Furthermore, although the age factor is an uncontroversial research variable extending from birth to death ( Cook 1995 ), and the CPH is a narrowly focused proposal subject to recurrent debate, ironically, it is the latter that tends to dominate SLA discussions ( García Lecumberri and Gallardo 2003 ), resulting in a number of competing conceptualizations. Thus, in the current literature on the subject ( Bialystok 1997 ; Richards and Schmidt 2002 ; Abello-Contesse et al. 2006), references can be found to (i) multiple critical periods (each based on a specific language component, such as age six for L2 phonology), (ii) the non-existence of one or more critical periods for L2 versus L1 acquisition, (iii) a ‘sensitive’ yet not ‘critical’ period, and (iv) a gradual and continual decline from childhood to adulthood.

It therefore needs to be recognized that there is a marked contrast between the CPH as an issue of continuing dispute in SLA, on the one hand, and, on the other, the popular view that it is an invariable ‘law’, equally applicable to any L2 acquisition context or situation. In fact, research indicates that age effects of all kinds depend largely on the actual opportunities for learning which are available within overall contexts of L2 acquisition and particular learning situations, notably the extent to which initial exposure is substantial and sustained ( Lightbown 2000 ).

Thus, most classroom-based studies have shown not only a lack of direct correlation between an earlier start and more successful/rapid L2 development but also a strong tendency for older children and teenagers to be more efficient learners. For example, in research conducted in the context of conventional school programmes, Cenoz (2003) and Muñoz (2006) have shown that learners whose exposure to the L2 began at age 11 consistently displayed higher levels of proficiency than those for whom it began at 4 or 8. Furthermore, comparable limitations have been reported for young learners in school settings involving innovative, immersion-type programmes, where exposure to the target language is significantly increased through subject-matter teaching in the L2 ( Genesee 1992 ; Abello-Contesse 2006 ). In sum, as Harley and Wang (1997) have argued, more mature learners are usually capable of making faster initial progress in acquiring the grammatical and lexical components of an L2 due to their higher level of cognitive development and greater analytical abilities.

In terms of language pedagogy, it can therefore be concluded that (i) there is no single ‘magic’ age for L2 learning, (ii) both older and younger learners are able to achieve advanced levels of proficiency in an L2, and (iii) the general and specific characteristics of the learning environment are also likely to be variables of equal or greater importance.

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Multilingual Pedagogy and World Englishes

Critical Period Hypothesis (CPH)

Tom Scovel writes, “The CPH [critical period hypothesis] is conceivably the most contentious issue in SLA because there is disagreement over its exact age span; people disagree strenuously over which facets of language are affected; there are competing explanations for its existence; and, to top it off, many people don’t believe it exists at all” (113). Proposed by Wilder Penfield and Lamar Roberts in 1959, the Critical Period Hypothesis (CPH) argues that there is a specific period of time in which people can learn a language without traces of the L1 (a so-called “foreign” accent or even L1 syntactical features) manifesting in L2 production (Scovel 48). If a learner’s goal is to sound “native,” there may be age-related limitations or “maturational constraints” as Kenneth Hyltenstam and Niclas Abrahamsson call them, on how “native” they can sound. Reducing the impression left by the L1 is certainly possible after puberty, but eliminating that impression entirely may not be possible.

Kenji Hakuta et al. explains that the relationship between age and L1 interference in L2 production is really not up for debate:

“The diminished average achievement of older learners is supported by personal anecdote and documented by empirical evidence….What is controversial, though, is whether this pattern meets the conditions for concluding that a critical period constrains learning in a way predicted by the theory” (31).

Some learners manage to overcome the “constraints” that Scovel believes are “probably accounted for by neurological factors that are genetically specified in our species” (114), but these learners are exceptional rather than the rule. It may be biology; it may be due to something else. The debate will continue, but evidence seems to indicate that the older learners become, the more difficult complete acquisition can be.

“David Birdsong, Looking Inside and Beyond the Critical Period Hypothesis.”  YouTube,  uploaded by IWL Channel, 09 May 2016, https://www.youtube.com/watch?v=9Bo0C4dj7Mw.

Application

Instructors should consider taking the CPH into account when assessing their students’ oral communication in the target language. When “maturational constraints” are a potential concern, it seems more fair for instructors to weight comprehension more heavily than nativeness. A thorough understanding of the CPH can also help instructors to counteract adult learners’ “self-handicapping” by helping the learners understand that, in spite of constraints due to aging, they are still capable of acquiring many–if not most–aspects of the target language.

Bibliography

Hakuta, Kenji, et al. “Critical Evidence: A Test of the Critical-Period Hypothesis for Second-Language Acquisition.”  Psychological Science , vol. 14, no. 1, 2003, pp. 31–38.  JSTOR , www.jstor.org/stable/40063748.

Hyltenstam, Kenneth, and Niclas Abrahamsson. “Comments on Stefka H. Marinova-Todd, D. Bradford Marshall, and Catherine E. Snow’s ‘Three Misconceptions about Age and L2 Learning’: Age and L2 Learning: The Hazards of Matching Practical ‘Implications’ with Theoretical ‘Facts.’”  TESOL Quarterly , vol. 35, no. 1, 2001, pp. 151–170.  JSTOR , www.jstor.org/stable/3587863.

Nemer, Randa. “Critical Period Hypothesis.”  Prezi,  04 Dec. 2013, https://prezi.com/zzuch40ibrlq/critical-period-hypothesis-sla/#.

Scovel, Tom.  Learning New Languages . Heinle & Heinle, 2001.

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Original research article, critical period in second language acquisition: the age-attainment geometry.

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  • Teachers College, Columbia University, New York City, NY, United States

One of the most fascinating, consequential, and far-reaching debates that have occurred in second language acquisition research concerns the Critical Period Hypothesis [ 1 ]. Although the hypothesis is generally accepted for first language acquisition, it has been hotly debated on theoretical, methodological, and practical grounds for second language acquisition, fueling studies reporting contradictory findings and setting off competing explanations. The central questions are: Are the observed age effects in ultimate attainment confined to a bounded period, and if they are, are they biologically determined or maturationally constrained? In this article, we take a sui generis , interdisciplinary approach that leverages our understanding of second language acquisition and of physics laws of energy conservation and angular momentum conservation, mathematically deriving the age-attainment geometry. The theoretical lens, termed Energy Conservation Theory for Second Language Acquisition, provides a macroscopic perspective on the second language learning trajectory across the human lifespan.

Introduction

The Critical Period Hypothesis (CPH), as proposed by [ 1 ], that nativelike proficiency is only attainable within a finite period, extending from early infancy to puberty, has generally been accepted in language development research, but more so for first language acquisition (L1A) than for second language acquisition (L2A).

In the context of L2A, there are two parallel facts that appear to compound the difficulty of establishing the validity of CPH. One is that there is a stark difference in the level of ultimate attainment between child and adult learners. “Children eventually reach a more native-like level of proficiency than learners who start learning a second language as adults” ([ 2 ], p . 360). But this fact exists alongside another fact, namely, that there are vast differences in ultimate attainment among older learners. [ 3 ] observed:

Although few adults, if any, are completely successful, and many fail miserably, there are many who achieve very high levels of proficiency, given enough time, input, and effort, and given the right attitude, motivation, and learning environment. ( p . 13).

The dual facets of inter-learner differential success are at the nexus of second language acquisition research. As [ 4 ] once noted:

One of the enduring and fascinating problems confronting researchers of second language acquisition is whether adults can ever acquire native-like competence in a second language, or whether this is an accomplishment reserved for children who start learning at a relatively early age. As a secondary issue, there is the question of whether those rare cases of native-like success reported amongst adult learners are indeed what they seem, and if they are, how it is that such people can be successful when the vast majority are palpably not. ( p . 219).

The primary question Kellerman raised here is, in essence, a critical period (CP) question, concerning differential attainment between child and adult learners, and his secondary question relates to differential attainment among adult learners.

As of this writing, neither question has been settled. Instead, the two phenomena are often seen conflated in debates, including taking evidence for one as counter-evidence for the other (see, e.g., [ 5 ]). By and large, it would seem that the debate has come down to a matter of interpretation; the same facts are interpreted differently as evidence for or against CPH (see, e.g., [ 5 – 7 ]). This state of affairs, tinted with ideological differences over the role of nature and/or nature in language development, continues to put a tangible understanding of either phenomenon out of reach, let alone a coherent understanding of both phenomena. In order to break out of the rut of ‘he said, she said,” we need to engage in systems thinking.

Our research sought to juxtapose child and adult learners, as some researchers have, conceptually, attempted (see, e.g., [ 8 – 11 ]). Specifically, we built on and extended an interdisciplinary model of L2A, Energy Conservation Theory for L2A (ECT-L2A) [ 12 , 13 ], originally developed to account for differential attainment among adult learners, to child learners. In so doing, we sought to gain a coherent understanding of the dual facets of inter-learner differential success in L2A, in addition to mathematically obtaining the geometry of the age-attainment function, a core concern of the CPH/L2A debate.

In what follows, we first provide a quick overview of the CPH research in L2A. We then introduce ECT-L2A. Next, we extend ECT-L2A to the age issue, mathematically deriving the age-attainment function. After that, we discuss the resultant geometry and the fundamental nature of CPH/L2A, and, more broadly, L2 attainment across the human lifespan. We conclude by suggesting a number of avenues for furthering the research on CPH within the framework of ECT-L2A.

However, before we proceed, it is necessary to note two “boundary conditions” we have set for our work. First, the linguistic domain in which we theorize inter-learner differential attainment concerns only the grammatical/computational aspects of language, or what [ 14 , 15 ] calls basic language cognition, which concerns aspects of language where native speakers show little variance. As [ 2 ] has aptly pointed out, much of the confusion in the CPH-L2A debate is attributable to a lack of agreement on the scope of linguistic areas affected by CP. Second, we are only concerned with naturalistic acquisition (i.e., acquisition happens in an input-rich or immersion environment), not instructed learning (i.e., an input-poor environment). These two assumptions are often absent in CPH/L2A research, leading to the different circumstances under which researchers interpret the CP notion and empirical results (for discussion, see [ 7 ]).

The critical period hypothesis in L2A

To date, two questions have dominated the research and debate on CPH/L2A: What counts as evidence of a critical period? What accounts for the age-attainment difference between younger learners and older learners? More than 4 decades of research on CPH/L2A- from [ 16 ] to [ 17 ] to [ 18 ]—have, in the main, found an inverse correlation between the age of acquisition (AoA) and the level of grammatical attainment (see also [ 19 ], for a meta-analysis); “the age of acquisition is strongly negatively correlated with ultimate second language proficiency for grammar as well as for pronunciation” ([ 20 ], p . 88).

However, views are almost orthogonal over whether the observed inverse correlation can count as evidence of CPH or the observed difference is attributable to brain maturation (see, e.g., [ 5 , 7 , 21 – 35 ]).

For some researchers, true evidence or falsification of CPH for L2A must be tied to whether or not late learners can attain a native-like level of proficiency (e.g., [ 36 ]). Others contend that the nativelikeness threshold, in spite of it being “the most central aspect of the CPH” ([ 2 ], p . 362), is problematic, arguing that monolingual-like native attainment is simply impossible for L2 learners [ 37 , 38 ]. Echoing this view, [ 39 ] offered:

[Sequential] bilinguals are not “two monolinguals in one” in any social, psycholinguistic, or cognitive neurofunctional sense. From this perspective, it is of questionable methodological value to quantify bilinguals’ linguistic attainment as a proportion of monolinguals’ attainment, with those bilinguals reaching 100% levels of attainment considered nativelike. ( p . 121).

In the meantime, empirical research into adult learners have consistently produced evidence of selective nativelike attainment, that is, nativelikeness is attained vis-à-vis some aspects of the target language but not others. These studies employed a variety of methodologies, including cross-sectional studies and longitudinal case studies (see, e.g., [ 40 – 56 ]). Some researchers (e.g., [ 55 , 57 ]) take the selective nativelikeness as falsifying evidence of CPH/L2A; other researchers disagree (see, e.g., [ 36 ]).

Leaving aside the vexed issue of nativelikeness, 1 Birdsong [ 58 ], among others, postulated that CPH/L2A must ultimately pass geometric tests: if studies comparing younger learners and older learners yield the geometry of a “stretched Z” for the age-attainment function, that would prove the validity of CPH/L2A, or falsify it, if otherwise. The stretched Z or inverted S [ 20 ] references a bounded period in which the organism exhibits heightened neural plasticity and sensitivity to linguistic stimuli from the environment. This period has certain temporal and geometric features. Temporally, it extends from early infancy to puberty, coinciding with the time during which the brain undergoes maturation [ 1 , 36 , 59 – 62 ]. Geometrically, this period should exhibit two points of inflection or discontinuities, viz, “an abrupt onset or increase of sensitivity, a plateau of peak sensitivity, followed by a gradual offset or decline, with subsequent flattening of the degree of sensitivity” ([ 58 ], p . 111).

By the temporal and geometric hallmarks, few studies seem to have confirmed CPH/L2A, not even those that have allegedly found stark evidence. A case in point is the [ 17 ] study, which reported what appears to be clear-cut evidence of CPH/L2A: r = −.87, p <.01 for the early age of arrival (AoA) group and r = −.16, p >.05 for the late AoA group. As Johnson and Newport described it, “test performance was linearly related to [AoA] up to puberty; after puberty, performance was low but highly variable and unrelated to [AoA],” which supports “the conclusion that a critical period for language acquisition extends its effects to second language acquisition” ( p . 60). However, this claim has been contested.

Focusing on the geometry of the results, [ 58 ] pointed out that the random distribution of test scores within the late AoA group “does not license the conclusion that “through adulthood the function is low and flat” or the corresponding interpretation that “the shape of the function thus supports the claim that the effects of age of acquisition are effects of the maturational state of the learner” ([ 17 ], p . 79)” ( p . 117). Birdsong argued that if CPH holds for L2A, the performance scores of the late AoA group should be distributed horizontally in addition to showing marginal correlation with age. Accordingly, the random distribution of scores could only be taken as indicative of “a lack of systematic relationship between the performance and the AoA and not of a “levelling off of ultimate performance among those exposed to the language after puberty” ([ 17 ], p . 79)” ([ 58 ], p . 118).

Interpreting the same study, other researchers such as [ 20 ] did not set their sights as much on the random distribution of the performance scores among the late learners as on the discontinuity between the early AoA and late AoA groups, arguing that the qualitative difference is sufficient evidence of CPH/L2A.

If geometric satisfaction is one flash point in CPH/L2A research, explaining random distribution of performance scores or, essentially, differential attainment among late learners counts as another. Analyses of late learners’ ultimate attainment (e.g., [ 10 , 22 , 26 , 43 , 63 – 67 ]) have yielded a host of cognitive, socio-psychological, or experiential factors that can be associated with inter-learner differential attainment among late learners. The question, then, is whether or not these non-age factors confound, or even interact with, the age or maturational effect (see discussion in [ 2 , 68 – 72 ]. As Newport [ 7 ] aptly asked, “why cannot other variables interact with age effects?” ( p . 929).

These are undoubtedly complex questions for which sophisticated solutions are needed—beyond the methodological repairs many have thought are solely needed in advancing CPH/L2A research (see, e.g., [ 19 , 67 ]). In the remainder of this article, we take a different tack to the age issue, adopting a theoretical, hybrid approach, ECT-L2A [ 12 , 13 ], to mathematically derive the age-attainment function.

Energy-Conservation Theory for L2A

ECT-L2A is a theoretical model originally developed to account for the divergent states of ultimate attainment in adult L2A [ 12 , 13 ]. Drawing on the physics laws of energy conservation and angular momentum conservation, it theorizes the dynamic transformation and conservation of internal energies (i.e., from the learner) and external energies (i.e., from the environment) in rendering the learner’s ultimate attainment. This model, thus, takes into account nature and nurture factors, and specifically, uses five parameters - the linguistic environment or input, learner motivation, learner aptitude, distance between the L1 and the target language (TL) and the developing learner—and their interaction to account for levels of L2 ultimate attainment.

ECT-L2A draws a number of parallels between mechanical energies and human learning energies: kinetic energy for motivation and aptitude energy, potential energy for environmental energy, 2 and centrifugal energy for L1-TL deviation energy (for discussion, see [ 12 ]). These energies each perform a unique yet dynamic role. As the learner progresses in the developmental process, the energies shift in their dominance, while the total energy remains constant.

Mathematically, ECT-L2A reads as follows:

where ζ r denotes the learner’s motivational energy, r the learner’s position in the learning process relative to the TL, η the distance between L1 and TL, and ρ the input of TL. According to Eq. 1 , the total learning energy, ∈ , comes from the sum of motivation energy ζ r , aptitude (a constant) Λ , deviation energy η 2 r 2 , and environmental energy - ρ r .

The energy types included in Eq. 1 are embodiments of nature and nurture contributions. The potential energy or TL traction, - ρ r , represents the external or environmental energy, while the kinetic or motivational energy, ζ r , along with aptitude, Λ , and the centrifugal or deviation energy η 2 r 2 represent the internal energies.

Under the overarching condition of the total energy being the same or conserved throughout the learning process, ϵ = constant , each type of energy performs a different role, with one converting to another over time as the position of the learner changes in the developmental process.

For mathematical and conceptual convenience, (1) is rewritten into (2) which contains the effective potential energy, U eff (r) .

where U e f f r = η 2 r 2 − ρ r . In other words, the effective potential energy is the sum of deviation energy and the potential energy (see further breakdown in the next section).

The L2A energy system as depicted here is true of every learner, meaning that the total energy is constant for a single learner. But the total energy varies from learner to learner. Accordingly, different learners may reach different levels of ultimate attainment (i.e., closer or more distant from the TL), r 0 . This is illustrated in Figure 1 , where r 0 and r 0 ′ represent the ultimate attainments for learners with different amounts of total energy, ϵ >0 or ϵ <0.

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FIGURE 1 . Inter-learner differential ultimate attainment as a function of different amounts of total energy: ϵ >0; ϵ < 0; ϵ = ϵ min [ 12 , 13 ].

Key to understanding Figure 1 is that it is the individual’s total energy that determines their level of attainment. Of the three scenarios on display here, ECT-L2A is only concerned with the case of ϵ ≥0, which represents the unbound process (r 0 , ∞), ignoring the bounded processes of ϵ < 0; ε = ϵmin.

The central thesis of ECT-L2A, as expressed in Eq. 1 , is that the moment a learner begins to receive substantive exposure to the TL, s/he enters a ‘gravitational’ field or a developmental ecosystem in which s/he is initially driven by kinetic or motivational energy, increasingly subject to the traction of the potential or environmental energy, but eventually stonewalled by the deviation energy or centrifugal barrier, resulting in an asymptotic endstate. This trajectory is further elaborated below.

The developmental trajectory depicted and forecast by ECT-L2A

The L2A trajectory begins with the learner at the outset of the learning process or at infinity (r = ∞). Initially, their progression toward the central source, i.e., the TL, is driven almost entirely by their motivation energy and aptitude, as expressed in Eq. 3 .

As learning proceeds, but with r still large (i.e., the learner still distant from the target) and the deviation energy much weaker than the environmental energy, η 2 r 2 ≪ ρ r (due to the second power of r ), the motivation energy rises as a result of its “interaction” with the environmental energy− ρ r , in which case the environmental energy transfers to the motivation energy. Mathematically, this is expressed in Eq. 4 .

As learning further progresses, the environmental energy - ρ r becomes dominant before yielding to the deviation energy η 2 r 2 . Eventually, the deviation energy overrides the environmental energy, as expressed in Eq. 1 , repeated below as Eq. 5 for ease of reference.

The deviation energy is so powerful that it draws the learner away from the target and their learning reaches an asymptote, where their motivation energy becomes minimal, ζ ( r 0 ) = 0, as expressed in Eq. 6 .

At this point, all other energies submit to the deviation energy, including the initial motivation energy ζ (∞) and some of the potential or environmental energy. Consequently, further exposure to TL input would not be of substantive help, meaning that it would not move the learner markedly closer to the target.

Figure 2 gives a geometric expression of the L1-TL deviation η, which is akin to the angular momentum of an object moving in a central force field [ 73 – 75 ]. The deviation from the TL, signifying the distance between the L1 and the TL, varies with different L1-TL pairings. For example, the distance index, according to the Automated Similarity Judgment Program Database [ 76 ], is 90.25 for Italian and English but 100.33 for Italian and Chinese.

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FIGURE 2 . Geometric description of the deviation parameter η .

Figure 3 illustrates differential ultimate attainment (indicated by r 0 ) as a function of the deviation parameter η. As η increases, the level of attainment is lower or the attainment is further away from the target ( r = 0).

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FIGURE 3 . Effective potentials U eff with different values of η [ 12 , 13 ].

For adult L2A, ECT-L2A predicts, inter alia , that high attainment is possible but full attainment is not. In other words, near-nativelike attainment is possible, but complete-nativelike attainment is not. ECT-L2A also predicts that while motivation and aptitude are part and parcel of the total energy of a given L2 learner, their role is largely confined to the earlier stage of development. Most of all, ECT-L2A predicts that the L1-L2 deviation is what keeps L2 attainment at asymptote.

For L2 younger learners, ECT-L2A also makes a number of predictions to which we now turn.

ECT-L2A vis-à-vis younger learners

As highlighted above, the deviation energy is what leads L2 attainment to an asymptote. It follows that as long as η (i.e., the L1-TL distance) is non-zero, the learner’s ultimate attainment, r 0 , will always eventuate in an asymptote. As shown in Figure 3 , the larger the deviation r 0 , the more distant the ultimate attainment r 0 is from the TL. Put differently, a larger η portends that learning would reach an asymptote earlier or that the ultimate attainment would be less native-like. But how does that work for child L2A?

On the ECT-L2A account, it is the low η value that determines child learners’ superior attainment. In child L2 learners, the deviation is low, because of the incipient or underdeveloped L1. However, as the L1 develops, the η value grows until it becomes a constant, presumably happening around puberty 3 , hence coinciding with the offset of the critical period [ 1 ]. As shown in Figures 1 , 3 , the smaller the deviation, η, the closer r 0 (i.e., the ultimate level of attainment) is to the TL or the higher the ultimate attainment.

From Eq. 6 the ultimate attainment of any L2 learner, irrespective of age, can be mathematically derived:

where ε = ϵ – Λ (i.e., total energy minus aptitude). r 0 here again denotes ultimate attainment. The upper panel in Figure 4 displays the geometry of ultimate attainment as a function of deviation, η.

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FIGURE 4 . Double non-linearity of r 0 η [ (A) : first non-linearity] and η t [ (B) : second non-linearity] at early AoA.

For a given child learner, η is a constant, but different child learners can have a different η value, depending on their AoA . Herein lies a crucial difference from adult learning where η is a constant for all learners because of their uniform late AoA or age of acquisition and because their L1 has solidified. Adult learning starts at a time when the deviation between their L1 and the TL has become fixed, so to speak, as a result of having mastered their L1 (see the lower panel of Figure 4 ).

Further, for child L2 learners, η is simultaneously a function of their AoA, a proxy for time ( t ), and can therefore be expressed as η(t). This deviation function of time varies in the range of 0 ≤ η t ≤ η max . Accordingly; Eq. 7 can be mathematically rewritten into (8):

Assuming that as t grows or as AoA increases, η increases slowly and smoothly from 0 to η max until it solidifies into a constant, which marks the onset of adult learning, η( t ) can mathematically be expressed as (9).

where a is a constant. The geometry of the deviation function of time is illustrated in the lower panel of Figure 4 .

Figure 4 displays a double non-linearity characterizing L2 acquisition by young learners, with (A) showing the first order of non-linearity of r 0 η , that is, ultimate attainment as a function of deviation or the L1-TL distance (computed via Eq. 7 ), and with (B) displaying the second order of non-linearity, η (t), that is, η changing with t , age of acquisition (computed through Eq. 9 ).

Figure 5 illustrates ultimate attainment as a function of AoA, r 0 (t), and its derivative against t , d r 0 d t , which naturally yields three distinct periods: a critical period, t critical ; a post-critical period, t p-critical ; and an adult learning period, t adult . Within the critical period, t critical , r 0 ≅ 0 , meaning there is no real difference in attainment as age of acquisition increases. But within the post-critical period, t p-critical , r 0 changes dramatically, with d r 0 d t peaking and waning until it drops to the level approximating that of the adult period. Within the adult period, t adult , r 0 remains a constant, as attainment levels off.

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FIGURE 5 . Ultimate attainment (the blue line) as a function of age of acquisition ( t ) and its derivatives giving three distinct periods (the orange line).

ECT-L2A, therefore, identifies three learning periods. First, there is a critical period, t critical , within which attainment is nativelike, r 0 ≅ 0. Notice that the blue line in Figure 5 is the lowest during the critical period, signifying that the attainment converges on the target, but it is the highest during the adult period, meaning that the attainment diverges greatly from the target. The offset of the critical period is smooth rather than abrupt, with the impact of deviation, η , slowly emerging at its offset. During this period, the L1 is surfacing, yet with negligible deviation from the TL and weak in strength.

Key to understanding this account of the critical period is the double non-linearity: first, ultimate attainment as a function of L1-TL deviation ( r 0 ( η ), see (A) in Figure 4 ); and second, L1-TL deviation as a function of AoA ( η ( t ); see (B) in Figure 4 ). Crucially, this double non-linearity extends a critical “point” into a critical “period” .

Second, there is a post-critical period, t p-critical , 0 < r 0 ≤ r 0 ( η max ), within which, with advancing AoA, the L1-L2 deviation grows larger and stronger, resulting in ultimate attainment that is increasingly lower (i.e., increasingly non-nativelike). The change rate of r 0 , its first derivative to time, d r 0 d t , is dramatic, waxing and waning. As such, the post-critical period is more complex and nuanced than the critical period. During the post-critical period, as the learner’s L1 becomes increasingly robust and developed, the deviation becomes larger, resulting in a level of attainment increasingly away from the target (i.e., increasingly non-nativelike).

Third, there is an adult learning period, t adult , η = η max ≅ constant, where, despite the continuously advancing AoA, the deviation reaches its maximum and remains a constant, as benchmarked in indexes of crosslinguistic distance (see, e.g., the Automated Similarity Judgment Program Database [ 76 ]). As a result, L2 ultimate attainment turns asymptotic (for discussion, see [ 12 , 13 ]).

The three periods mathematically produced by ECT-L2A coincide with the stretched “Z” slope that some researchers have argued (e.g., [ 17 , 58 , 59 ]) constitutes the most unambiguous evidence for CPH/L2A, and by extension, for a maturationally-based account of the generic success or lack thereof (i.e., nativelike or non-nativelike L2 proficiency) in early versus late starters. For better illustration of the stretched “Z,” we can convert Figure 5 into Figure 6 , using Eq. 10 .

where a t t stands for level of attainment. According to Eq. 10 , the smaller the r 0 is, the higher the attainment is.

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FIGURE 6 . Level of attainment as a function of AoA.

In sum, ECT-L2A mathematically establishes the critical period geometry. That said, the geometry, as seen in Figure 6 , exhibits anything but abrupt inflections; the phase transitions are gradual and smooth. The adult period, for example, does not exhibit a complete “flattening” but markedly lower attainment with continuous decline (cf. [ 7 , 23 , 28 ]). 4

Explaining CPH/L2A

As is clear from the above, on the ECT-L2A account of the critical period, η (i.e., L1-TL deviation) is considered an inter-learner variable and, at once, a proxy for age of acquisition, t . More profoundly, however, ECT-L2A associates η with neural plasticity or sensitivity (cf [ 77 ]). The relationship between plasticity, p ( t ), and deviation function, η (t) , is expressed as (11):

Thus, the relationship between plasticity and the deviation function is one of inverse correlation. During the critical period, η = η min (i.e., minimal L1-TL deviation) and p = p max (i.e., maximal plasticity); conversely, during the adult learning period, η = η max (i.e., maximal L1-TL deviation) and p = p min (i.e., minimal plasticity). In short, an increased deviation, η (t) , corresponds to a decrease of plasticity, p (t) , and vice versa , as illustrated in Figure 7 .

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FIGURE 7 . Plasticity as a function of age of acquisition.

Illustrated in Figure 7 is that neural plasticity, first proposed by [ 78 ] as the underlying cause of CP, is at its highest during the critical period and, as [ 79 ] put it, it “endures within the confines of its onset and offset” ( p . 182). But it begins to decline and drops to a low level during the post-critical period, and remains low through the adult learning period. 5 It would, therefore, seem reasonable to call the first period “critical” and the second period “sensitive.” It is worth mentioning in passing that the post-critical or sensitive period has thus far received scant empirical attention in CPH/L2A research.

Temporally, following the [ 59 ] conjecture, the critical period should last through early childhood from birth to age six, and the sensitive period should offset around puberty (see also [ 2 , 20 , 36 , 67 , 71 ]). Crucially, both periods are circumscribed, exhibiting discontinuities, with the critical period exhibiting maximal sensitivity, the sensitive period declining, though, for the most part, still far greater, sensitivity than the adult learning period. This view of a changing underlying mechanism across the three periods of AoA and attainment resonates with the Language as a Complex Adaptive System perspective (see, e.g., [ 80 ]). [ 81 ], for example, noted that “the processing mechanisms that underlie [language development] … are fundamentally non-linear. This means that development itself will frequently have phase-like characteristics, that there may be periods of extreme sensitivity to input (‘critical periods’)” ( p . 431).

ECT-L2A as a unifying model

ECT-L2A, by virtue of identifying the L1-TL deviation, η, as a lynchpin for age effects, provides an explanation for the differential ultimate attainment of early versus late starters. Essentially, in early AoA, η is a temporal and neuro-functional proxy tied respectively to a developing L1 and to a changing age and changing neuroplasticity. In contrast, in late AoA, η is a constant, due to the L1 being fully developed and the brain fully mature. This takes care of the first facet of inter-learner differential attainment. What about the second facet, viz., the inter-learner differential attainment among late learners?

ECT-L2A (as expressed in Eq. 1 ) is a model of an ecosystem where there is an interplay between learner-internal and environmental energies. In line with the general finding from L2 research that individual difference variables are largely responsible for inter-learner differential attainment of nativelike proficiency in adult learners (see, e.g., [ 27 , 35 , 77 , 82 , 83 ]), ECT-L2A specifically ties motivation and aptitude to kinetic energy, only to provide a more nuanced picture of the changing magnitude of individual difference variables.

Figure 8 illustrates the twin facets of inter-learner differential attainment. First, attainment varies as a function of AoA. Second, attainment varies within and across the three learning periods as a function of individual learners with different amounts of total energy, ϵ 1 < ϵ 2 < ϵ 3 . As shown, individual differences play out the least among learners of AoA falling within the critical period but the most within the adult learning period, consistent with the general findings from L2 research (see, e.g., [ 2 , 3 , 43 , 63 , 65 , 67 , 84 , 85 ]). During the post-critical or sensitive period, individual differences are initially non-apparent but become more pronounced with increasing AoA. 6

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FIGURE 8 . Level of attainment for total energies ϵ 1 < ϵ 2 < ϵ 3 .

ECT-L2A thus offers a coherent explanation for variable attainment in late learners. First and foremost, it posits that individual learners’ total energy or “carrying capacity” [ 86 ] is different, which leads to different levels of attainment. Second, although the internal (motivation and aptitude) and external (environment) energies interact over time, ultimately it is the deviation energy η 2 r 2 that dominates and stalls the learner at asymptote (see Eq. 6 ). This account provides a much more nuanced perspective on the role of individual differences than has been given in the current L2A literature.

Extant empirical studies investigating individual difference variables through correlation analysis have mostly projected a static view of the role (some of) the variables play in L2A. In contrast, ECT-L2A gives a dynamic view and, more importantly, an interactive view. In the end, the individual difference variables are part of a larger ecosystem within which they do not act alone, but rather interact with other energies (i.e., potential energy and deviation energy), waxing and waning as a result of energy conservation.

In this article, we engaged with a central concern in the ongoing heated debate on CPH/L2A, that is, the geometry of age differences. Within the framework of ECT-L2A, an interdisciplinary model of L2 attainment, we mathematically derived the age-attainment function and established the presence of a critical period in L2A. Importantly, this period is part of a developmental trajectory that comprises three learning periods: a critical period, a post-critical or sensitive period, and an adult period.

ECT-L2A has thus far demonstrated a stunning internal consistency in that it mathematically identifies younger learners’ superior performance to adult learners’ as well as the differential attainment among adult learners.

ECT-L2A, while in broad agreement with an entrenchment-transfer account from L2A research that essentializes the role of the L1 in L2 attainment (see, e.g., [ 5 , 11 , 87 – 90 ]), provides a dynamic account of that role and its varying contributions to the different age-related learning periods. Furthermore, ECT-L2A offers an interactive account whereby the L1, as part of the deviation energy, interacts with other types of learner-internal and learner-external energies. Above all, ECT-L2A, by virtue of summoning internal and external energies, gives a coherent explanation for the twin facets of inter-learner differential success—as respectively manifested between younger and older learners and among older learners.

Validation of ECT-L2A is, however, required. Many questions warrant investigation. On this note, Johnson and Newort’s view [ 17 ], in particular, that the goal of any L2A theory should be to account for three sets of facts—a) gradual decline of performance, b) the age at which a decline in performance is detected, and c) the nature of adult performance—resonates with us. Although ECT-L2A shines a light on all three, further work is clearly needed. More specific to the focus of the present article, three sets of questions can be asked in relation to the three learning periods ECT-L2A has identified.

In the spirit of promoting collective intelligence, we present a subset of these questions below in the hope that they will spark interest among researchers across disciplines and inspire close-up investigations leveraging a variety of methodologies.

First, for the critical period:

1. When does the decline of learning begin?

2. How does it relate to the status of L1?

3. What is plasticity like in this period?

4. What does plasticity entail?

5. How is it related to a developing L1 and a developing L2?

Answers to these questions can, at least in part, be found in the various literatures across disciplines. But approaching these questions in relation to one another—as opposed to discretely—would likely yield a more systematic, holistic and coherent understanding. Or perhaps, in search of answers to any of these questions, one may realize that the existing understanding is way too shallow or inadequate. For instance, [ 18 ] cited “a lack of interference from a well-learned first language” as one of the possible causes of the age-attainment function in younger versus older learners. But what has not yet been established is the nature of the younger learners’ L1. What does “well-learned” mean? Is it established or is it still developing? At minimum, it cannot be a unitary phenomenon, given the age span of young learners.

Second, for the post-critical or sensitive period, ECT-L2A mathematically identifies two sub-periods. Thus, questions such as the following should be examined:

6. What prompts the initial dramatic decline of attainment?

7. How does each of the sub-periods relate to the status of L1?

8. How does the decline relate to changing plasticity?

9. How does it relate to grammatical performance?

Third, for the adult learning period, questions such as the following warrant close engagement:

10. How do learners with the same L1 background differ from each other in their L2 ultimate attainment?

11. How do learners with different L1 backgrounds differ from one another in their L2 ultimate attainment?

12. How is the trajectory of each type of energy, endogenous or exogenous, related to the level of attainment?

Investigating these questions, among others, will lead us to a better understanding not only of the critical period but also of L2 learning over the arc of human life.

The theoretical and practical importance of gaining a robust and comprehensive understanding of how age affects the L2 learning outcome calls for systematic investigations. To that end, ECT-L2A has offered a systems thinking perspective and framework.

Data availability statement

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.

Author contributions

All authors listed have made a substantial, direct, and intellectual contribution to the work and approved it for publication.

Acknowledgments

We greatly appreciate the insightful and perceptive comments made by the reviewers on an earlier version of this article, and take sole responsibility for any error or omission.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

1 Despite the centrality of “nativelikeness” to the Critical Period Hypothesis [ 1 ], studies in L2A have increasingly moved away from the use of the term in favor of “the level of ultimate attainment” [ 2 ].

2 The potential energy in ECT-L2A is akin to gravitational potential energy. As such it defines the central source field, serving as the primary energy that dynamically converts to other types of energy: kinetic energy and centrifugal energy. Similarly, the potential energy of L2A defines the field of learning. It stands for TL environment or input, serving as primary energy, dynamically converting to motivational and L1-TL deviation energies. An essential premise of ECT-L2A is the existence of potential energy. This premise is consistent with that underpinning L2A studies on CPH and ultimate attainment.

3 That is when the L1 becomes entrenched.

4 Looking back on the [ 17 ] study, [ 7 ], taking account of developments in the intervening 3 decades in understanding changes in the brain during adulthood, updated the earlier assertation about the stability of age effects in adulthood, noting that “it is more accurate to hypothesize that L2 proficiency SHOULD continue to decline during adulthood” and that “a critical or sensitive period for language acquisition is not absolute or sudden” ( p . 929, emphasis in original). She further argued that “[t]he lack of flattening of age function at adulthood in many studies does not mean that learning is not constrained by biologically based maturational changes” (ibid).

5 The plasticity never completely disappears, but rather becomes asymptotic.

6 Age and attainment function appears to follow a power law in that age effects are greatest during the critical period, less so during the post-critical or sensitive period, and weakest during the adult learning period (see Figure 8 ). Similarly, Figure 7 exhibits a power law relationship between age and plasticity: Plasticity is at its peak during the critical period, declines during the post-critical or sensitive period, and plateaus in the adult learning period.

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Keywords: ultimate attainment, critical period, second language acquisition, physics laws, energy conservation, angular momentum conservation, inter-learner differential attainment

Citation: Han Z and Bao G (2023) Critical period in second language acquisition: The age-attainment geometry. Front. Phys. 11:1142584. doi: 10.3389/fphy.2023.1142584

Received: 11 January 2023; Accepted: 02 March 2023; Published: 20 March 2023.

Reviewed by:

Copyright © 2023 Han and Bao. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: ZhaoHong Han, [email protected]

This article is part of the Research Topic

Social Physics and the Dynamics of Second Language Acquisition

EnglishPost.org

The Critical Period Hypothesis

The Critical Period Hypothesis was first proposed by Montreal neurologist Wilder Penfield and co-author Lamar Roberts in their 1959 book Speech and Brain Mechanisms , and was popularized by Eric Lenneberg in 1967 with Biological Foundations of Language.

The C ritical Period Hypothesis is the subject of a long-standing debate in linguistics and language acquisition over the extent to which the ability to acquire language is biologically linked to age.

The hypothesis claims that there is an ideal time window to acquire language in a linguistically rich environment , after which further language acquisition becomes much more difficult and effortful.

The critical period hypothesis states that the first few years of life is the crucial time in which an individual can acquire a first language if presented with adequate stimuli.

If language input doesn’t occur until after this time, the individual will never achieve a full command of language—especially grammatical systems.

The evidence for such a period is limited, and support stems largely from theoretical arguments and analogies to other critical periods in biology such as visual development, but nonetheless is widely accepted

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The Critical Period Hypothesis in Second Language Acquisition

More on second language acquisition.

The theory has often been extended to a critical period for second-language acquisition (SLA), although this is much less widely accepted.

Certainly, older learners of a second language rarely achieve the native-like fluency that younger learners display, despite often progressing faster than children in the initial stages.

David Singleton states that in learning a second language, “younger = better in the long run,” but points out that there are many exceptions, noting that five percent of adult bilinguals master a second language even though they begin learning it when they are well into adulthood—long after any critical period has presumably come to a close.

While the window for learning a second language never completely closes, certain linguistic aspects appear to be more affected by the age of the learner than others.

For example, adult second-language learners nearly always retain an immediately identifiable foreign accent, including some who display perfect grammar (Oyama 1976).

Some writers have suggested a younger critical age for learning phonology than for syntax. Singleton (1995) reports that there is no critical period for learning vocabulary in a second language.

Critical Period Hypothesis has been a topic of significant debate and research in the field of language acquisition for decades.

I hope this article has contributed to your knowledge of it

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Critical period effects in second language learning: the influence of maturational state on the acquisition of English as a second language

  • PMID: 2920538
  • DOI: 10.1016/0010-0285(89)90003-0

Lenneberg (1967) hypothesized that language could be acquired only within a critical period, extending from early infancy until puberty. In its basic form, the critical period hypothesis need only have consequences for first language acquisition. Nevertheless, it is essential to our understanding of the nature of the hypothesized critical period to determine whether or not it extends as well to second language acquisition. If so, it should be the case that young children are better second language learners than adults and should consequently reach higher levels of final proficiency in the second language. This prediction was tested by comparing the English proficiency attained by 46 native Korean or Chinese speakers who had arrived in the United States between the ages of 3 and 39, and who had lived in the United States between 3 and 26 years by the time of testing. These subjects were tested on a wide variety of structures of English grammar, using a grammaticality judgment task. Both correlational and t-test analyses demonstrated a clear and strong advantage for earlier arrivals over the later arrivals. Test performance was linearly related to age of arrival up to puberty; after puberty, performance was low but highly variable and unrelated to age of arrival. This age effect was shown not to be an inadvertent result of differences in amount of experience with English, motivation, self-consciousness, or American identification. The effect also appeared on every grammatical structure tested, although the structures varied markedly in the degree to which they were well mastered by later learners. The results support the conclusion that a critical period for language acquisition extends its effects to second language acquisition.

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Critical Period in Brain Development: Definition, Importance

Toketemu has been multimedia storyteller for the last four years. Her expertise focuses primarily on mental wellness and women’s health topics. 

critical theory hypothesis

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  • When Does the Critical Period Begin and End?
  • The Critical Period Hypothesis—What It States
  • What Happens to the Brain in the Critical Period?
  • What Kind of Events Impact the Brain During the Critical Period?
  • How Do Adverse Events Impact the Brain?
  • What's the Difference Between a Critical Period and a Sensitive Period?
  • What Happens to the Brain When the Critical Period Ends?

The critical period in brain development is an immensely significant and specific time frame during which the brain is especially receptive to environmental stimuli and undergoes a series of rapid changes. 

These changes have lifelong effects as essential neural connections and pathways are established, playing a vital role in cognitive, emotional, and social development. 

This article will explore the timeline, impacting events, and subsequent consequences of the critical period on brain development. It also explores the distinction between critical periods and sensitive periods and what happens to the brain once the critical period ends.

When Does the Critical Period Begin and End? 

The starting point of the critical period is at conception. The brain starts to form and develop from the moment you are conceived. During pregnancy, a baby's brain is already beginning to shape itself for the world outside. The brain is gearing up and getting ready to absorb a massive amount of information.

The Early Years of a Child's Life

Once the baby is born, the brain kicks into high gear. The early years of a child's life, from birth to around the age of five, are generally considered the core of the critical period. The brain is incredibly absorbent during these years, taking in information rapidly. Everything from language to motor skills to social cues is being learned and processed extensively.

Different aspects of learning and development have different critical periods. For instance, the critical period for language acquisition extends into early adolescence. This means that while the brain is still very good at learning languages during early childhood, it continues to be relatively efficient at it until the teenage years.

The brain is incredibly absorbent during these years, taking in information rapidly. Everything from language to motor skills to social cues is being learned and processed extensively.

Vision Develops During This Period

On the other hand, for certain sensory abilities like vision, the critical period might end much earlier. This means that the brain is most receptive to developing visual abilities in the first few years of life, and after that, it becomes significantly harder to change or improve these abilities.

The Critical Period Hypothesis—What It States 

The brain has a certain time window when it's exceptionally good at learning new things, especially languages. This window of time is what is referred to as the "critical period."

Younger People Learn Languages Faster Than Older People

Eric Lenneberg, a neuropsychologist, introduced the Critical Period Hypothesis. He was very interested in how people learn languages . Through his observations and research, Lenneberg noticed that younger people were much more adept at learning languages than older people. This observation led him to the idea that there is a specific period during which the brain is highly efficient and capable of absorbing languages.

As You Age, It Becomes More Difficult to Absorb New Information

If the critical period is a wide open window in the early years of life, allowing the brain to take in an abundance of information quickly and efficiently, as time progresses, this window begins to close gradually. As it closes, the brain becomes less capable of easily absorbing languages.

This doesn't mean that learning becomes impossible as you age; it merely indicates that the ease and efficiency with which the brain learns start to decline.

What Happens to the Brain in the Critical Period? 

During the critical period, the brain experiences explosive growth. Let's take a look at some of the changes that happen in the brain during the critical period.

Neurons Form Connections

In the early stages, neurons in the brain start to form connections. These connections are called synapses.

Synapses are bridges that help different parts of the brain communicate with each other. In the critical period, the brain is building these bridges at an incredible pace.

Neuroplasticity Strengthens Brain Connections

As a baby interacts with the world, certain connections strengthen while others weaken. For instance, if a baby hears a lot of music, the parts of the brain associated with sounds and music will become stronger. This process of strengthening certain connections is known as brain plasticity because the brain molds itself like plastic.

Attachment to Primary Caregivers

An essential aspect of the critical period is the development of attachment to caregivers. During the early months and years, babies and toddlers form strong bonds with the people caring for them .

These attachments are critical for emotional development. When a caregiver responds to a baby's needs with warmth and care, the baby learns to form secure attachments . This lays the foundation for healthy relationships later in life.

What Happens When Children Are Not Given Attention?

What if a child is not given the attention and care they need during the critical period? This is a significant concern. Without proper attention and stimulation, the brain doesn't develop as effectively. The bridges or connections that should be built might not form properly. This can lead to various issues, including difficulty forming relationships, emotional problems, and learning difficulties.

When a child is given proper attention, stimulation, and care during the critical period, their brain thrives. The connections form rapidly and robustly. This sets the stage for better learning, emotional regulation, and relationship-building throughout life.

What Kind of Events Impact the Brain During the Critical Period? 

When a child is exposed to a rich, stimulating environment where they can play, explore, and learn, it tremendously impacts the brain. Engaging in interactive learning, being read to, and having supportive relationships with caregivers can significantly contribute to a well-developed brain.

Events such as abuse, neglect, head trauma , or extreme stress—collectively known as adverse childhood experiences (ACEs)—can be detrimental to brain development. These adverse events can impede the formation of neural connections and lead to behavioral, emotional, and cognitive difficulties later in life. "Unfortunately, disruptions to normal brain development due to environmental influences such as poverty, neglect, or exposure to toxins can cause lasting damage. This is why it is so important for children to receive adequate nutrition, stimulation, and parental care during these first few years of life; without it, they may suffer developmental delays and other issues that could potentially be avoided with proper attention,"  Harold Hong, MD , a board-certified psychiatrist says.

How Do Adverse Events Impact the Brain? 

When a child is neglected or abused, stress can impact how their brain develops. The parts of the brain involved in emotions and handling stress might not develop properly. This can make it hard for the person to manage their emotions later in life.

The hippocampus, involved in learning and memory, and the amygdala, which plays a role in emotion processing, are especially vulnerable. 

Similarly, if a child does not have enough food to eat or a safe place to live, the chronic stress of these conditions can impact brain development. The brain might focus on survival instead of other important areas of development, like learning and building relationships.

Even accidents that cause head injuries can impact the brain during the critical period. If a child experiences head trauma, it can affect the brain's development depending on the injury's severity and location.

What's the Difference Between a Critical Period and a Sensitive Period?

It is imperative to distinguish between critical periods and sensitive periods.

  • Critical periods are specific windows of time during development when the brain is exceptionally receptive to certain types of learning and experiences. Once this period is over, acquiring those skills or attributes becomes significantly more challenging.
  • Sensitive periods are phases in which the brain is more responsive to certain experiences. It's easier to learn or be influenced by specific experiences during sensitive periods, but unlike critical periods, missing this timeframe doesn't make it impossible to acquire those skills or traits later.

For example, while there is a critical period for acquiring native-like pronunciation and grammar, there is also a sensitive period for language learning. Children are more adept at learning new languages when they are young, but even if someone misses this window, they can still learn languages later in life.

One way to visualize the difference is to think of critical periods as a tightly defined window of time with a clear beginning and end, during which certain development must occur. In contrast, sensitive periods are more like a gradual slope, where learning at the beginning is optimal, but the ability doesn't disappear entirely over time.

What Happens to the Brain When the Critical Period Ends? 

It's essential to recognize that the end of the critical period does not mean the end of learning or brain development. Instead, it signifies a shift in how the brain learns and adapts. 

During the critical period, the brain is highly plastic, meaning it can change and form new connections rapidly. As this period ends, the brain doesn't lose this plasticity entirely, but the rate at which it can make new connections slows down. 

According to Hong, although some of these connections can still be altered by experiences later in life, such as learning a new language or practicing a skill, it is much harder to make significant changes after the critical period has ended. This highlights just how important it is for parents to provide proper care and nurture during those first few years.

The Brain Becomes More Specialized Via Adult Plasticity

The brain also becomes more specialized in the skills and information it has acquired as this period ends. During the critical period, the brain forms numerous connections, and as it ends, it starts to use these connections more efficiently for specialized tasks.

Even though the critical period ends, the brain still possesses a degree of plasticity and continues to learn throughout life. This is called adult plasticity.

Adult plasticity is not as robust during the critical period, but it allows for the continuous adaptation and learning necessary for us to navigate the ever-changing demands of life.

The conventional view is that critical periods close relatively tightly. However, research has started to challenge this rigid view. It's more accurate to say that the doors of critical periods close but do not necessarily lock.

While the brain's plasticity decreases after these periods, learning and adaptation can still take place, albeit with more effort and over a longer time. This phenomenon of 'metaplasticity'—the brain's ability to change its plasticity levels—remains an exciting area of ongoing research,  Dr. Ryan Sultan , a neuroscientist, child psychiatrist, and professor of psychiatry at Columbia University, says. 

What This Means For You

The critical period represents an invaluable window during which the foundations for cognitive, emotional, and social abilities are established. The environment, experiences, and attachments formed during this period have far-reaching consequences on a person's life.  Understanding the nuances of the critical period is essential for educators, parents, and policymakers to create nurturing environments that support healthy brain development. Providing support and early interventions for children exposed to adverse experiences is vital for ensuring their potential is not hindered by the circumstances of their early life.

Siahaan F. The critical period hypothesis of sla eric lenneberg’s . Journal of Applied Linguistics . 2022;2(1):40-45.

Nelson CA, Gabard-Durnam LJ. Early adversity and critical periods: neurodevelopmental consequences of violating the expectable environment. Trends in Neurosciences. 2020;43(3):133-143.

Colombo J, Gustafson KM, Carlson SE. Critical and sensitive periods in development and nutrition. Ann Nutr Metab . 2019;75(Suppl. 1):34-42.

Patton MH, Blundon JA, Zakharenko SS. Rejuvenation of plasticity in the brain: opening the critical period. Current Opinion in Neurobiology . 2019;54:83-89.

By Toketemu Ohwovoriole Toketemu has been multimedia storyteller for the last four years. Her expertise focuses primarily on mental wellness and women’s health topics.

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Critical period hypothesis

The critical period hypothesis says that there is a period of growth in which full native competence is possible when acquiring a language. This period is from early childhood to adolescence.

A young learner

The critical period hypothesis has implications for teachers and learning programmes, but it is not universally accepted. Acquisition theories say that adults do not acquire languages as well as children because of external and internal factors, not because of a lack of ability.

Example Older learners rarely achieve a near-native accent. Many people suggest this is due to them being beyond the critical period.

In the classroom A problem arising from the differences between younger learners and adults is that adults believe that they cannot learn languages well. Teachers can help learners with this belief in various ways, for example, by talking about the learning process and learning styles, helping set realistic goals, choosing suitable methodologies, and addressing the emotional needs of the adult learner.

Further links:

https://www.teachingenglish.org.uk/article/how-maximise-language-learning-senior-learners

https://www.teachingenglish.org.uk/article/how-much-do-your-learners-use-english-outside-classroom

Research and insight

Browse fascinating case studies, research papers, publications and books by researchers and ELT experts from around the world.

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Critical Period Hypothesis

The critical period hypothesis is the subject of a long-standing debate in linguistics and language acquisition over the extent to which the ability to acquire language is biologically linked to age. The hypothesis claims that there is an ideal ‘window’ of time to acquire language in a linguistically rich environment, after which further language acquisition becomes much more difficult and effortful.

The critical period hypothesis states that the first few years of life is the crucial time in which an individual can acquire a first language if presented with adequate stimuli. If language input doesn’t occur until after this time, the individual will never achieve a full command of language—especially grammatical systems.

The evidence for such a period is limited, and support stems largely from theoretical arguments and analogies to other critical periods in biology such as visual development, but nonetheless is widely accepted. The nature of this phenomenon, however, has been one of the most fiercely debated issues in psycholinguistics and cognitive science in general for decades. Some writers have suggested a “sensitive” or “optimal” period rather than a critical one; others dispute the causes (physical maturation, cognitive factors). The duration of the period also varies greatly in different accounts. In second language acquisition, the strongest evidence for the critical period hypothesis is in the study of accent, where most older learners do not reach a native-like level. However, under certain conditions, native-like accent has been observed, suggesting that accent is affected by multiple factors, such as identity and motivation, rather than a critical period biological constraint (Moyer, 1999; Bongaerts et al., 1995; Young-Scholten, 2002).

The critical period hypothesis was first proposed by Montreal neurologist Wilder Penfield and co-author Lamar Roberts in a 1959 paper Speech and Brain Mechanisms, and was popularised by Eric Lenneberg in 1967 with Biological Foundations of Language.

Lenneberg states that there are maturational constraints on the time a first language can be acquired. First language acquisition relies on neuroplasticity. If language acquisition does not occur by puberty, some aspects of language can be learnt but full mastery cannot be achieved. This was called the “critical period hypothesis.”

An interesting example of this is the case of Genie. A thirteen-year-old victim of lifelong child abuse, Genie was discovered in her home on November 4, 1970, strapped to a potty chair and wearing diapers. She appeared to be entirely without language. Her father had judged her retarded at birth and had chosen to isolate her, and so she had remained until her discovery.

It was an ideal opportunity to test the theory that a nurturing environment could somehow make up for a total lack of language past the age of 12. She was unable to acquire language completely, although the degree to which she acquired language is disputed.

Detractors of the “Critical Period Hypothesis” point out that in this example and others like it (see Feral children), the child is hardly growing up in a nurturing environment, and that the lack of language acquisition in later life may be due to the results of a generally abusive environment rather than being specifically due to a lack of exposure to language.

Recently, it has been suggested that if a critical period does exist, it may be due at least partially to the delayed development of the prefrontal cortex in human children. Researchers have suggested that delayed development of the prefrontal cortex and a concomitant delay in the development of cognitive control may facilitate convention learning, allowing young children to learn language far more easily than cognitively mature adults and older children. This pattern of prefrontal development is unique to humans among similar mammalian (and primate) species, and may explain why humans—and not chimpanzees—are so adept at learning language.

Second language acquisition

The theory has often been extended to a critical period for second language acquisition (SLA), although this is much less widely accepted. Certainly, older learners of a second language rarely achieve the native-like fluency that younger learners display, despite often progressing faster than children in the initial stages. David Singleton states that in learning a second language, “younger = better in the long run,” but points out that there are many exceptions, noting that five percent of adult bilinguals master a second language even though they begin learning it when they are well into adulthood—long after any critical period has presumably come to a close.

While the window for learning a second language never completely closes, certain linguistic aspects appear to be more affected by the age of the learner than others. For example, adult second-language learners nearly always retain an immediately identifiable foreign accent, including some who display perfect grammar (Oyama 1976). Some writers have suggested a younger critical age for learning phonology than for syntax. Singleton (1995) reports that there is no critical period for learning vocabulary in a second language. Robertson (2002)] observed that factors other than age may be even more significant in successful second language learning, such as personal motivation, anxiety, input and output skills, settings and time commitment.

On reviewing the published material, Bialystok and Hakuta (1994) conclude that second-language learning is not necessarily subject to biological critical periods, but “on average, there is a continuous decline in ability [to learn] with age.”

Experimental and observational studies

How children acquire native language (L1) and the relevance of this to foreign language (L2) learning has long been debated. Although evidence for L2 learning ability declining with age is controversial, a common notion is that children learn L2s easily, whilst older learners rarely achieve fluency. This assumption stems from ‘critical period’ (CP) ideas. A CP was popularised by Eric Lenneberg in 1967 for L1 acquisition, but considerable interest now surrounds age effects on second language acquisition (SLA). SLA theories explain learning processes and suggest causal factors for a possible CP for SLA, mainly attempting to explain apparent differences in language aptitudes of children and adults by distinct learning routes, and clarifying them through psychological mechanisms. Research explores these ideas and hypotheses, but results are varied: some demonstrate pre-pubescent children acquire language easily, and some that older learners have the advantage, whilst others focus on existence of a CP for SLA. Recent studies (e.g. Mayberry and Lock, 2003) have recognised certain aspects of SLA may be affected by age, whilst others remain intact. The objective of this study is to investigate whether capacity for vocabulary acquisition decreases with age.

Other work has challenged the biological approach; Krashen (1975) re-analysed clinical data used as evidence and concluded cerebral specialisation occurs much earlier than Lenneberg calculated. Therefore, if a CP exists, it does not coincide with lateralisation. Despite concerns with Lenneberg’s original evidence and the dissociation of lateralisation from the language CP idea, however, the concept of a CP remains a viable hypothesis, which later work has better explained and substantiated.

Effects of aging

A review of SLA theories and their explanations for age-related differences is necessary before considering empirical studies. The most reductionist theories are those of Penfield and Roberts (1959) and Lenneberg (1967), which stem from L1 and brain damage studies; children who suffer impairment before puberty typically recover and (re-)develop normal language, whereas adults rarely recover fully, and often do not regain verbal abilities beyond the point reached five months after impairment. Both theories agree that children have a neurological advantage in learning languages, and that puberty correlates with a turning point in ability. They assert that language acquisition occurs primarily, possibly exclusively, during childhood as the brain loses plasticity after a certain age. It then becomes rigid and fixed, and loses the ability for adaptation and reorganisation, rendering language (re-)learning difficult. Penfield and Roberts (1959) claim children under nine can learn up to three languages: early exposure to different languages activates a reflex in the brain allowing them to switch between languages without confusion or translation into L1 (Penfield, 1964). Lenneberg (1967) asserts that if no language is learned by puberty, it cannot be learned in a normal, functional sense. He also supports Penfield and Roberts’ (1959) proposal of neurological mechanisms responsible for maturational change in language learning abilities. This, Lenneberg maintains, coincides with brain lateralisation and left-hemispherical specialisation for language around age thirteen: infants’ motor and linguistic skills develop simultaneously, but by age thirteen the cerebral hemispheres’ functions separate and become set, making language acquisition extremely difficult (Lenneberg, 1967).

Deaf and feral children

Cases of deaf and feral children provide evidence for a biologically determined CP for L1. Feral children are those not exposed to language in infancy/childhood due to being brought up in the wild, in isolation and/or confinement. A classic example is ‘Genie’, who was deprived of social interaction from birth until discovered aged thirteen (post-pubescent). She was completely without language, and after seven years of rehabilitation still lacked linguistic competence. Another case is ‘Isabelle’, who was incarcerated with her deaf-mute mother until the age of six and a half (pre-pubescent). She also had no language skills, but, unlike Genie, quickly acquired normal language abilities through systematic specialist training.

Such studies are however problematic; isolation can result in general retardation and emotional disturbances, which may confound conclusions drawn about language abilities. Studies of deaf children learning American Sign Language (ASL) have fewer methodological weaknesses. Newport and Supalla (1987) studied ASL acquisition in deaf children differing in age of exposure; few were exposed to ASL from birth, most of them first learned it at school.

Results showed a linear decline in performance with increasing age of exposure; those exposed to ASL from birth performed best, and ‘late learners’ worst, on all production and comprehension tests. Their study thus provides direct evidence for language learning ability decreasing with age, but it does not add to Lennerberg’s CP hypothesis as even the oldest children, the ‘late learners’, were exposed to ASL by age four, and had therefore not reached puberty, the proposed end of the CP. In addition, the declines were shown to be linear, with no sudden ‘drop off’ of ability at a certain age, as would be predicted by a strong CP hypothesis. That the children performed significantly worse, however, suggests the CP may end earlier than originally postulated.

Behavioural approaches

Contrary to biological views, behavioural approaches assert that languages are learned as any other behaviour, through conditioning. Skinner (1957) details how operant conditioning forms connections with the environment through interaction and, alongside O. Hobart Mowrer (1960), applies the ideas to language acquisition. Mowrer hypothesises that languages are acquired through rewarded imitation of ‘language models’; the model must have an emotional link to the learner (e.g. parent, spouse), as imitation then brings pleasant feelings which function as positive reinforcement. Because new connections between behaviour and the environment are formed and reformed throughout life, it is possible to gain new skills, including language(s), at any age.

To accommodate observed language learning differences between children and adults, Felix (1985) describes that children, whose brains create countless new connections daily, may handle the language learning process more effectively than do adults. This assumption, however, remains untested and is not a reliable explanation for children’s aptitude for L2 learning. Problematic of the behaviourist approach is its assumption that all learning, verbal and non-verbal, occurs through the same processes. A more general problem is that, as Pinker (1995) notes, almost every sentence anybody voices is an original combination of words, never previously uttered, therefore a language cannot consist only of word combinations learned through repetition and conditioning; the brain must contain innate means of creating endless amounts of grammatical sentences from a limited vocabulary. This is precisely what Chomsky (1965) argues with his proposition of a Universal Grammar (UG).

Universal Grammar

Chomsky (1965) asserts that environmental factors must be relatively unimportant for language emergence, as so many different factors surround children acquiring L1. Instead, Chomsky claims language learners possess innate principles building a ‘language acquisition device’ (LAD) in the brain. These principles denote restricted possibilities for variation within the language, and enable learners to construct a grammar out of ‘raw input’ collected from the environment. Input alone cannot explain language acquisition because it is degenerated by characteristic features such as stutters, and lacks corrections from which learners discover incorrect variations.

Singleton and Newport (2004) demonstrate the function of UG in their study of ‘Simon’. Simon learned ASL as his L1 from parents who had learned it as an L2 after puberty and provided him with imperfect models. Results showed Simon learned normal and logical rules and was able to construct an organised linguistic system, despite being exposed to inconsistent input. Chomsky developed UG to explain L1 acquisition data, but maintains it also applies to L2 learners who achieve near-native fluency not attributable solely to input and interaction (Chomsky, 1965).

Although it does not describe an optimal age for SLA, the theory implies that younger children can learn languages more easily than older learners, as adults must reactivate principles developed during L1 learning and forge an SLA path: children can learn several languages simultaneously as long as the principles are still active and they are exposed to sufficient language samples (Pinker, 1995). The parents of Singleton and Newport’s (2004) patient also had linguistic abilities in line with these age-related predictions; they learned ASL after puberty and never reached complete fluency.

Problems within UG Theory for L2 acquisition

There are, however, problems with the extrapolation of the UG theory to SLA: L2 learners go through several phases of types of utterance that are not similar to their L1 or the L2 they hear. Other factors include the cognitive maturity of most L2 learners, that they have different motivation for learning the language, and already speak one language fluently. Other studies also highlight these problems: Dehaene (1999) investigates how cerebral circuits used to handling one language adapt for the efficient storage of two or more. He reports observations of cerebral activation when reading and translating two languages. They found the most activated brain areas during the tasks were not those generally associated with language, but rather those related to mapping orthography to phonology. They conclude that the left temporal lobe is the physical base of L1, but the L2 is ‘stored’ elsewhere, thus explaining cases of bilingual aphasia where one language remains intact. They maintain that only languages learned simultaneously from birth are represented, and cause activity, in the left hemisphere: any L2 learned later is stored separately (possibly in the right hemisphere), and rarely activates the left temporal lobe.

This suggests that L2 may be qualitatively different from L1 due to its dissociation from the ‘normal’ language brain regions, thus the extrapolation of L1 studies and theories to SLA is placed in question. A further disadvantage of UG is that supporting empirical data are taken from a limited sample of syntactic phenomena: a general theory of language acquisition should cover a larger range of phenomena. Despite these problems, several other theorists have based their own models of language learning on it; amongst others Felix’ (1985) ‘competing cognitive systems’ idea. These ideas are supported by empirical evidence, which consequently supports Chomsky’s ideas. Due to this support and its descriptive and explanatory strength, many theorists regard UG as the best explanation of language, and particularly grammar, acquisition.

UG and the critical period hypothesis

A key question about the relationship of UG and SLA is: is the language acquisition device posited by Chomsky and his followers still accessible to learners of a second language? Research suggests that it becomes inaccessible at a certain age (see Critical Period Hypothesis), and learners increasingly depended on explicit teaching (see pedagogical effects above, and age below). In other words, although all of language may be governed by UG, older learners might have great difficulty in gaining access to the target language’s underlying rules from positive input alone.

Piaget (1926) is one psychologist reluctant to ascribe specific innate linguistic abilities to children: he considers the brain a homogeneous computational system, with language acquisition being one part of general learning. He agrees this development may be innate, but claims there is no specific language acquisition module in the brain. Instead, he suggests external influences and social interaction trigger language acquisition: information collected from these sources constructs symbolic and functional schemata (thought or behaviour patterns). According to Piaget, cognitive development and language acquisition are life-long active processes that constantly update and re-organise schemata. He proposes children develop L1 as they build a sense of identity in reference to the environment, and describes phases of general cognitive development, with processes and patterns changing systematically with age. Piaget assumes language acquisition is part of this complex cognitive development, and that these developmental phases are the basis for an optimal period for language acquisition in childhood. Interactionist approaches derived from Piaget’s ideas supports his theory. Some studies (e.g. Newport and Supalla, 1987) show that, rather than abrupt changes in SLA ability after puberty, language ability declines with age, coinciding with declines in other cognitive abilities, thus supporting Piaget.

Several researchers, however, remain unconvinced that language acquisition is part of general development: Felix (1985) claims cognitive abilities alone are useless for language learning, as only vocabulary and meaning are connected to cognition; lexicology and related meanings have conceptual bases. Felix’ criticism of the assumption that L2 fluency simply requires skilful applications of the correct rules is supported by the lack of psychological empirical evidence for Piaget’s idea.

Although Krashen (1975) also criticises this theory, neither he nor Felix discredit the importance of age for second language acquisition. Krashen (1975), and later Felix (1985), proposed theories for the close of the CP for L2 at puberty, based on Piaget’s cognitive stage of formal operations beginning at puberty, as the ‘ability of the formal operational thinker to construct abstract hypotheses to explain phenomena’ inhibits the individual’s natural ability for language learning.

The term “language acquisition” became commonly used after Stephen Krashen contrasted it with formal and non-constructive “learning.” Today, most scholars use “language learning” and “language acquisition” interchangeably, unless they are directly addressing Krashen’s work. However, “second language acquisition” or “SLA” has become established as the preferred term for this academic discipline.

Though SLA is often viewed as part of applied linguistics, it is typically concerned with the language system and learning processes themselves, whereas applied linguistics may focus more on the experiences of the learner, particularly in the classroom. Additionally, SLA has mostly examined naturalistic acquisition, where learners acquire a language with little formal training or teaching.

Other directions of research

Impact of illiteracy

Virtually all research findings on SLA to date build on data from literate learners. Tarone, Bigelow and Hansen (2009) find significantly different results when replicating standard SLA studies with low literate L2 learners. Specifically, learners with lower alphabetic literacy levels are significantly less likely to notice corrective feedback on form or to perform elicited imitation tasks accurately. These findings are consistent with research in cognitive psychology showing significant differences in phonological awareness between literate and illiterate adults (Reis and Castro-Caldas 1997; Castro-Caldas et al. 1998). An important direction for SLA research must therefore involve the exploration of the impact of alphabetic literacy on cognitive processing in second language acquisition.

Empirical research has attempted to account for variables detailed by SLA theories and provide an insight into L2 learning processes, which can be applied in educational environments. Recent SLA investigations have followed two main directions: one focuses on pairings of L1 and L2 that render L2 acquisition particularly difficult, and the other investigates certain aspects of language that may be maturationally constrained. Flege, Mackay and Piske (2002) looked at bilingual dominance to evaluate two explanations of L2 performance differences between bilinguals and monolingual-L2 speakers, i.e. a maturationally defined CP or interlingual interference.

Bilingual dominance

Flege, Mackay and Piske investigated whether the age at which participants learned English affected dominance in Italian-English bilinguals, and found the early bilinguals were English (L2) dominant and the late bilinguals Italian (L1) dominant. Further analysis showed that dominant Italian bilinguals had detectable foreign accents when speaking English, but early bilinguals (English dominant) had no accents in either language. This suggests that, though interlingual interference effects are not inevitable, their emergence, and bilingual dominance, may be related to a CP.

Sebastián-Gallés, Echeverría and Bosch (2005) also studied bilinguals and highlight the importance of early language exposure. They looked at vocabulary processing and representation in Spanish-Catalan bilinguals exposed to both languages simultaneously from birth in comparison to those who had learned L2 later and were either Spanish- or Catalan-dominant. Findings showed ‘from birth bilinguals’ had significantly more difficulty distinguishing Catalan words from non-words differing in specific vowels than Catalan-dominants did (measured by reaction time).

These difficulties are attributed to a phase around age eight months where bilingual infants are insensitive to vowel contrasts, despite the language they hear most. This affects how words are later represented in their lexicons, highlighting this as a decisive period in language acquisition and showing that initial language exposure shapes linguistic processing for life. Sebastián-Gallés et al. (2005) also indicate the significance of phonology for L2 learning; they believe learning an L2 once the L1 phonology is already internalised can reduce individuals’ abilities to distinguish new sounds that appear in the L2.

Age effects on grammar learning

Most studies into age effects on specific aspects of SLA have focused on grammar, with the common conclusion that it is highly constrained by age, more so than semantic functioning. B. Harley (1986) compared attainment of French learners in early and late immersion programs. She reports that after 1000 exposure hours, late learners had better control of French verb systems and syntax. However, comparing early immersion students (average age 6.917 years) with age-matched native speakers identified common problem areas, including third person plurals and polite ‘vous’ forms. This suggests grammar (in L1 or L2) is generally acquired later, possibly because it requires abstract cognition and reasoning (B. Harley, 1986).

B. Harley also measured eventual attainment and found the two age groups made similar mistakes in syntax and lexical selection, often confusing French with the L1. The general conclusion from these investigations is that different aged learners acquire the various aspects of language with varying difficulty. Some variation in grammatical performance is attributed to maturation (discussed in B. Harley, 1986), however, all participants began immersion programs before puberty and so were too young for a strong critical period hypothesis to be directly tested.

This corresponds to Noam Chomsky’s UG theory, which states that while language acquisition principles are still active, it is easy to learn a language, and the principles developed through L1 acquisition are vital for learning an L2.

Scherag, Demuth, Rösler, Neville and Röder (2004) also suggest learning some syntactic processing functions and lexical access may be limited by maturation, whereas semantic functions are relatively unaffected by age. They studied the effect of late SLA on speech comprehension by German immigrants to the U.S.A. and American immigrants to Germany. They found that native-English speakers who learned German as adults were disadvantaged on certain grammatical tasks but performed at near-native levels on lexical tasks. These findings are consistent with work by Hahne (2001, cited in Scherag et al., 2004).

Semantic functions acquisition

One study that specifically mentions semantic functions acquisition is that of Weber-Fox and Neville (1996). Their results showed that Chinese-English bilinguals who had been exposed to English after puberty, learned vocabulary to a higher competence level than syntactic aspects of language. They do, however, report that the judgment accuracies in detecting semantic anomalies were altered in subjects who were exposed to English after sixteen years of age, but were affected to a lesser degree than were grammatical aspects of language. It has been speculated (Neville and Bavelier, 2001, and Scherag et al., 2004) that semantic aspects of language are founded on associative learning mechanisms, which allow life-long learning, whereas syntactical aspects are based on computational mechanisms, which can only be constructed during certain age periods. Consequently, it is reasoned, semantic functions are easier to access during comprehension of an L2 and therefore dominate the process: if these are ambiguous, understanding of syntactic information is not facilitated. These suppositions would help explain the results of Scherag et al.’s (2004) study.

Advantages of bilingual education for children

It is commonly believed that children are better suited to learn a second language than are adults. However, general second language research has failed to support the critical period hypothesis in its strong form (i.e., the claim that full language acquisition is impossible beyond a certain age). According to Linda M. Espinosa, especially in the United States the number of children growing up with a home language that is not English but Spanish is constantly increasing. Therefore these children have to learn the English language before kindergarten as a second language. It is better to dispose young children to maintain both, their home language and their second language. Cultivating his home language, the child creates his own cultural identity and becomes aware of his roots. This fact leads to the question whether having the ability to speak two languages helps or harms young children. Research shows that the acquisition of a second language in early childhood confers several advantages, especially a greater awareness of linguistic structures. Furthermore it is advantageous for young children to grow up bilingually because they do not need to be taught systematically but learn languages intuitively. How fast a child can learn a language depends on several personal factors, such as interest and motivation, and its learning environment. Communication should be facilitated rather than a child should be forced to learn a language with strict rules. Education in early childhood can lead to an effective educational achievement for children from various cultural environments.

Another aspect that is worth considering is that bilingual children are often doing code switching which does not mean that the child is not able to separate the languages. The reason for code switching is the child’s lack of vocabulary in a certain situation. The acquisition of a second language in early childhood broadens the children’s minds and enriches them more than it harms them. Thus they are not only able to speak two languages in spite of being very young but they also acquire knowledge about the different cultures and environments. It is possible that one language can dominate. This depends on how much time is spent on learning each language.

Evolutionary Explanations for the Critical Period in First and Second Language Acquisition

Hurford’s Model

In order to provide evidence for the evolutionary functionality of the critical period in language acquisition, Hurford (1991) generated a computer simulation of plausible conditions of evolving generations, based on three central assumptions:

  • Language is an evolutionary adaptation that is naturally selected for.
  • Any given individual’s language can be quantified or measured.
  • Various aspects of maturation and development are under genetic control, which would extend to determine the timing for critical periods for certain capacities (i.e. polygenic inheritance).

According to Hurford’s evolutionary model, language acquisition is an adaptation that has survival value for humans, and that knowing a language correlated positively with an individual’s reproductive advantage. This finding is in line with views of other researchers such as Chomsky (1982) and Pinker & Bloom (1990). For example, Steven Pinker and Paul Bloom argue that due to the fact that language is a complex design that serves a specific function that cannot be replaced by any other existing capacity, the trait of language acquisition can be attributed to natural selection.

However, while arguing that language itself is adaptive and “did not ‘just happen’” (p.172), Hurford suggests that the critical period is not an adaptation, but rather a constraint on language that emerged due to a lack of selection pressures that reinforce acquiring more than one language. In other words, Hurford explains the existence of a critical period with genetic drift, the idea that when there are no selection pressures on multiple alleles acting on the same trait, one of the alleles will gradually diminish through evolution. Because the simulation reveals no evolutionary advantage of acquiring more than one language, Hurford suggests that the critical period evolved simply as a result of a lack of selection pressure.

Komarova and Nowak’s Dynamical System

Komarova and Nowak (2001) supported Hurford’s model, yet pointed out that it was limited in the sense that it did not take into account the costs of learning a language. Therefore, they created their own algorithmic model, with the following assumptions:

  • Language ability correlates with an individual’s reproductive fitness
  • The ability to learn language is inherited
  • There are costs to learning a language

Their model consists of a population with constant size, where language ability is a predictor of reproductive fitness. The learning mechanism in their model is based on Chomsky’s (1980, 1993) language acquisition device (LAD) and the notion of universal grammar. The results of their model show that the critical period for language acquisition is an “evolutionarily stable strategy (ESS)” (Komarova & Nowak, 2001, p. 1190). They suggest that this ESS is due to two competing selection pressures. First, if the period for learning is short, language does not develop as well, and thus decreases the evolutionary fitness of the individual. Alternatively, if the period for learning language is long, it becomes too costly to the extent that it reduces reproductive opportunity for the individual, and therefore limits reproductive fitness. Therefore, the critical period is an adaptive mechanism that keeps these pressures at equilibrium, and aims at optimal reproductive success for the individual.

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  11. The Critical Period Hypothesis in Second Language Acquisition: A ...

    Delineating the scope of the critical period hypothesis. First, the age span for a putative critical period for language acquisition has been delimited in different ways in the literature .Lenneberg's critical period stretched from two years of age to puberty (which he posits at about 14 years of age) , whereas other scholars have drawn the cutoff point at 12, 15, 16 or 18 years of age .

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    Language learned outside this critical period, Lenneberg hypothesized, would develop neither normally nor sufficiently. Given the nature of Lenneberg's (1967) Critical Period Hypothesis (CPH), however, affirmative or negative empirical proof for a critical period governing first language acquisition is intrinsically difficult to come by.

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    The 'critical period hypothesis' (CPH) is a particularly relevant case in point. This is the claim that there is, indeed, an optimal period for language acquisition, ending at puberty. However, in its original formulation ( Lenneberg 1967 ), evidence for its existence was based on the relearning of impaired L1 skills, rather than the ...

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