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date: 20 April 2024



  • Inanna Hamati-AtayaInanna Hamati-AtayaDepartment of International Politics, Aberystwyth University


Behavioralism is an approach in political science that became predominant in American social sciences from the 1950s until well into the 1970s. The Behavioral Revolution in American political science began as a “protest” against “traditional” political science, which it views as being both too descriptive and too speculative, lacking rigor and ambition, and incapable of analytical theorization and therefore of cognitive growth. Behavioralism opened up the discipline to various theories and methods imported from the social and pure sciences. Behavioralists replaced political philosophy with the philosophy of science, thereby setting new standards for the formulation of concepts, hypotheses, theories, and protocols for empirical testing. Behavioralism thus represents a sharp break from the previous discipline. Two “great” debates mark behavioralism as a paradigm: the first was between “realism” and “idealism” over the what-question concerning the discipline’s subject matter, while the second was about “methodology” and the how-question. Recently, some scholars have called for a revival of behavioral international relations (IR) as a subfield concerned with the explanation of the behavior of leaders, rather than states —an approach that refocuses behavioralism on the individual as a unit of analysis and on the underlying processes that account for political judgment and decisions. Whether such a research program can reclaim behavioralism’s place among the leading paradigms of IR, or whether the discipline is ready to welcome such a revival, is unclear.


  • International Relations Theory


Behavioralism is a paradigm that became predominant in American social sciences from the 1950s until well into the 1970s. Grounded in a belief in the unity of science and the unity of human behavior, behavioralism developed scientific, quantitative methodologies for the study of political processes, and opened up the discipline to a wide range of theories and methods imported from the social and pure sciences. Because they believed that political phenomena could be subjected to the methods of science, behavioralists turned their back on the normative legacy of the discipline and replaced political philosophy with the philosophy of science, thereby setting new standards for the formulation of concepts, hypotheses, theories, and protocols for empirical testing. Although behavioralism's paradigmatic reign did not last beyond the 1980s, it transformed the discipline so profoundly that it remains to this day an essential, albeit implicit, component of its identity.

Because of behavioralism's inscription in different socio-intellectual contexts that are all relevant for understanding its emergence, development, content, and impact on political science and international relations, and for the understanding of which it is also relevant, a reference essay on behavioralism necessarily takes multiple risks and has to avoid several pitfalls. The first is to present the tenets of this school of thought independently of the specific socio-intellectual context of both the American society and the American academy, thereby offering an unreflexive, decontextualized, and ahistorical account that fails to convey the relationship between cognitive consensus and socio-historical constraints, and that simultaneously fails to reconstruct the meaning this particular research program had for its main actors and opponents. Alternatively, the danger is to give context too great a weight in the assessment of the content, value, and contributions of behavioral(ist) research, thereby imprisoning it in its own historicity, and failing to appreciate the intellectual importance of its scholars' input, of the profound dilemmas they raised, and of the equally legitimate objections they faced.

At a second, related level, one has to avoid succumbing to the existent disciplinary narrative of IR, which is the only social science to view and tell its story as a succession of “great debates,” with all the dichotomies, oppositions, and narratives of exclusion and conflict such written history entails. Insofar as behavioralism was a contending party in IR's “second debate,” it is particularly difficult to extract it both from the textbook histories of the field and from its scholars' institutionalized memory of it. While this can be said of all the theories, paradigms, and cognitive doctrines that populate IR textbooks, it is especially problematic for behavioralism, which is often viewed as having “professionalized” the discipline (Waever 1997). Any reference to behavioralism will therefore be inevitably inscribed in intellectual and discursive strategies that aim to assess the development of IR as a cognitive field of production, as well as its identity as an autonomous academic discipline.

With these problems and constraints in mind, this essay presents behavioralism as a historical contribution to, and reflection on, recurrent and fundamental cognitive problems in the field. The essay starts with the context in which behavioralism emerged, then engages the Behavioral Revolution in American political science and presents its main epistemic, ontological, and axiological tenets. It then moves more specifically to behavioralism in IR, and to the terms of its “second debate.” The essay concludes with an assessment of behavioralism's legacy in a post-behavioralist era.

Behavioralism in Context: An American School of Thought

“Behavioralism” finds its disciplinary and intellectual roots in “behaviorism,” a school of psychology founded by James B. Watson and influenced by the work of physiologist Jacques Loeb (Lasswell 1950:553). Behaviorist psychology “attempted to resolve the dispute about the content, structure, and processes of human consciousness by evading all questions about the content of the ‘little black box’,” focusing instead “on the relationship between the stimulus as it acts on the black box and the black box as it reacts to the stimulus” (Merkl 1969:142).

It thereby followed the lead of animal psychology, which operated on the basis that introspective inquiry being impossible, one could only study animals' behavior (Mead 1934). The logic of extracting the study of human beings from introspection and from the limited and problematic understanding of the inner workings of the human mind and volition therefore became particularly attractive for social psychologists, who considered that unlike intentions, motivations, ideas, or beliefs, behavior could be understood with a great measure of rigor and objectivity if the right scientific methods were applied. As behaviorism, and then behavioralism, developed, these limitations were progressively waived and behavioralists started concerning themselves “with the processes of cognition, feelings, and with evaluations of human consciousness” (Merkl 1969:143). (On the differences between behaviorism and behavioralism, see Easton 1962.)

In the United States, behavioralism spread from psychology to the rest of the social sciences, gaining a stronghold at the University of Chicago, which became from the 1950s onwards a place where some of the most renowned behavioralists coexisted with some of their most renowned and strongest opponents. In political science the Chicago School, led by Charles E. Merriam, had since the 1920s explicitly criticized the “established tradition” of “institutionalism” for its limitations and its inability to produce a rigorous understanding of political processes (Truman 1969:50). “Anxious to secure federal financing for social science research, but apprehensive that some unenlightened ‘persons confound social science and socialism’,” its scholars coined the term “behavioral science” and shifted the ontological focus of political science research to the concept of “political behavior” (Somit and Tanenhaus 1967:183). (For early Chicago School research, see Schuman 1935; Lasswell 1936, 1948; Gosnell 1937; Merriam 1939, 1945; Merriam and Gosnell 1949.)

For some behavioralists, “the existence of some key attitudes and predispositions generated in the American culture” such as “pragmatism, factmindedness,” and “confidence in science” (Dahl 1969:69) explains the success of behavioralism in the United States. In the United Nations Educational, Scientific and Cultural Organization's (UNESCO) 1950 report on the state of “Contemporary Political Science” in the world, Harold Lasswell thus writes “[i]n America, one does not appreciate political theories that do not lead to any empirical study and have no influence on the conduct of public affairs … Americans respect science and technology, and our specialists in political science dream of a field where authority is founded on experimental results and not on dialectic alone” (Lasswell 1950:552; my translation; in the same volume, see also Cook 1950:83; Merriam 1950:255). These statements are meaningful at least because of their performative nature and as illustrations of the new spirit that had taken hold of American political science, which, in its behavioral branch, was pursuing the project of a “science of politics” as it was conceived at the turn of the twentieth century, thereby breaking away from the philosophical roots of the discipline.

Whether or not the “American culture” can be credited for the “rapid flowering of the behavioral approach in the US” (Dahl 1969:69), the impression that behavioralism is a specifically American phenomenon is shared by both American and non-American scholars, as manifested in Hedley Bull's (1966) critique of behavioralist IR. Similar scientific research had undoubtedly been attempted elsewhere – e.g., British mathematician Lewis Fry Richardson's theory of war (see Rapoport 1957) – but the United States provided a definitely more favorable milieu for the propagation of such an intellectual movement. Behavioralism's success can, however, better be explained by the convergence of the interests and concerns of American social scientists on the one hand, with those of the American government and public agencies on the other. In post-1945 America, government officials needed reliable input from scientific disciplines that would help them understand the roots and causes of different social, national, and international problems, assess their possibilities for action, and predict or anticipate future outcomes and changes. At the time, economics was the only social science to have gained such credibility in the eyes of academics and politicians alike.

American social scientists, on the other hand, were keen on demonstrating the relevance of their fields of study for practical social problems. In this specific socio-intellectual setting, political science suffered from a composite complex of inferiority and an acute existential crisis over the “state of the discipline,” which were due to a combination of several factors:

the discovery that the talents and skills of political scientists were not highly valued by governmental personnel officers; the disconcerting realization, by those who did spend some time in the public service, of the profound difference between the “accepted wisdom” of the profession and the reality of the governmental process; the inability of traditional political science to account for the rise of fascism, national socialism, and communism, or to explain the continuation of these regimes in power; a growing sensitivity to, and unhappiness with, the basically descriptive nature of the discipline; and a knowledge of apparent advances in other social sciences and a mounting fear that political science was lagging behind its sister professions.

(Somit and Tanenhaus 1967:184)

Electoral processes and voting behavior, in particular, had been subjected to sophisticated and impressive analyses by sociologists and social psychologists who, with the use of survey methods, were turning their craft into a very appealing empirical science.

Quantitative studies were themselves facilitated by the development and wider use of computers, which made it possible to use complex mathematical and statistical computations. Behavioralist political scientists therefore imported from other disciplines the successful methods they thought would ground their analyses in scientific and rigorous methodologies. This explains the emergence of a new generation of scholars who were trained in cognitive areas that had never before been relevant to political science itself, such as mathematics, physics, biology, economics, sociology, and psychology.

The specific impact on American political science of sociology and psychology was also triggered by the arrival in the 1930s of a significant number of European – mainly German – émigrés, who brought with them a new intellectual culture that exposed their American colleagues to the works of Weber, Marx, Durkheim, Freud, Pareto, and others, to a new philosophy of knowledge (logical positivism), and to a wide range of analytical concepts and social theories that would be crucial to the development of behavioral science (Somit and Tanenhaus 1967:184; Dahl 1969:69).

Most of these European scholars were in fact radically opposed to behavioralism (Gunnell 1993, 2006), with the notable exceptions of Heinz Eulau and Karl Deutsch. The intellectual tradition that traveled with them to the United States took on a different meaning and served very different research agendas. At the University of Chicago, where Leo Strauss and Hans Morgenthau battled for the preservation of the philosophical legacy of the discipline, the Department of Political Science was producing a new generation of influential behavioralist scholars who would bring prestige to the Chicago School and to the entire discipline – most notoriously, Harold Lasswell (1936, 1948), V.O. Key, Jr. (1956, 1968, 1969), David B. Truman (1951), Herbert Simon (1947), Gabriel Almond (1950), David Easton (1953, 1965), Quincy Wright (1942, 1955), and Morton A. Kaplan (1957). Behavioralism became prominent at Harvard with Karl Deutsch (1963) and Sidney Verba (1961), Almond's collaborator (Almond and Verba 1963), at Yale with Robert A. Dahl (1961) and at Stanford with Eulau (1966, 1977, 1986; see also Eulau, Eldersveld, and Janowitz 1956; Eulau, Wahlke, and Buchanan 1962; Eulau and Prewitt 1973; Eulau and Wahlke 1978).

Behavioralism also benefited from the support of the major American funding agencies. The Social Science Research Council (SSRC) established in 1945 a Committee on Political Behavior that was chaired by a behavioralist and was naturally “behaviorally inclined.” The Carnegie, Rockefeller, and Ford Foundations played an important role in promoting behavioral research, the latter having its own behavioral science program. Behavioralist scholars soon monopolized the allocation of grants, to the point that “access to public funds was largely limited to the social sciences deemed worthy of the appellation ‘behavioral sciences’” (Somit and Tanenhaus 1967:185).

The 1950s proved to be a turning point for behavioralism in both American political science and American IR. It was not unusual after that point for behavioralists to occupy the most prestigious and influential positions in the profession, including the presidency of the American Political Science Association (APSA) and membership in the SSRC. While political theory and its normative, ethical tradition of inquiry had constituted the core of the discipline since its establishment in the United States (Gunnell 1993), behavioralism succeeded in marginalizing and even stigmatizing philosophically oriented scholars, thereby monopolizing much of the American scholarly production of the field. It also profoundly reshaped its cognitive tenets, terminology, methodologies, and scholarly ethos, while redefining its relationship to the other social (and the nonsocial) sciences. (For further readings on behavioralism in the development of political science, see Crick 1959; Somit and Tanenhaus 1967; Baer et al. 1991; Gunnell 1993; Easton 1997.)

The Terms of the Behavioral Revolution

For the behavioralists as well as their critics, the debate around behavioralism was grounded in the opposition and tension between “innovation” and “tradition” (Eulau 1969). The Behavioral Revolution starts as a declared “protest” (Dahl 1969) against “traditional” political science, which it views as being both too descriptive and too speculative, lacking rigor and ambition, and incapable of analytical theorization and therefore of cognitive growth. David Easton (1953) famously diagnosed the discipline as undergoing a deep “malaise” that made its practitioners incapable of justifying their institutional existence and intellectual relevance to the problems of the age. For the behavioralists, the problem originated in the discipline's attachment and grounding in both philosophy and history, which prevented it from developing rigorous explanations of specific political processes, and grounded its discourse in general and obscure assumptions wherein concepts such as “human nature” and “power” remained hermetic to scientific explanation.

The answer to the discipline's crisis was delineated in Easton's (1962:7–8) definition of the behavioralist creed, which is subtended by a belief in both the unity of science and the unity of human behavior.


Regularities: There are discoverable uniformities in political behavior [that] … can be expressed in generalizations or theories with explanatory and predictive value.


Verification: The validity of such generalizations must be testable, in principle, by reference to relevant behavior.


Techniques: Means for acquiring and interpreting data … need to be examined self-consciously, refined, and validated.


Quantification: Precision in the recording of data and the statement of findings require measurement and quantification …


Values: Ethical evaluation and empirical explanation involve two different kinds of propositions that, for the sake of clarity, should be kept analytically distinct …


Systematization: … [T]heory and research are to be seen as closely intertwined parts of a coherent and orderly body of knowledge …


Pure science: … [T]he understanding and explanation of political behavior logically precede and provide the basis for efforts to utilize political knowledge in the solution of urgent practical problems of society.


Integration: Because the social sciences deal with the whole human situation, political research can ignore the findings of other disciplines only at the peril of weakening the validity and undermining the generality of its own results …

The Science of Political Behavior and Processes

The first important tenet of behavioralism is that the social sciences can be as “scientific” in their methods, modes of explanation, and conclusions as the “pure sciences,” the same understanding of “science” prevailing in both. The objective, then, was to discover regularities and patterns of behavior similar to the “laws” observed in nature. Given that social organization and human behavior are governed by dynamic processes rather than static patterns of repetition, the scientific models that were emulated were those of biology, where systems are conceptualized on the basis of their functions and interactions with their environment, rather than those of physics, where explanation derives from the effect of “covering laws” of behavior on the properties of individual or aggregate bodies. This explains why systems theory (Easton 1953, 1965; Kaplan 1957) and cybernetics (Deutsch 1963, 1978) became predominant in behavioralist literature, as they provided behavioralists with the conceptual framework for the study of political processes in terms of social adaptation, equilibrium, information processing, and homeostatic regulation. (On the influence of scientific paradigms on political science, see Schubert et al. 1983.)

The realm of political science per se was therefore epistemically conceived in positivist terms, insofar as science concerns itself with “givens,” that is, observable facts or, at most, observable manifestations of nonfactual phenomena. “Behavior” therefore took ontological precedence over such notions as “human nature,” “freedom,” “reason,” or “power.” This positivist epistemology, however, should be understood as defining the realm of science, not of knowledge in general. Although many behavioralists adopted positivism and even scientism as comprehensive attitudes toward the social world, most of them did acknowledge that behavioral science cannot encompass the realm of understanding, and that many dimensions of human behavior and politics can only be grasped by relying on historical, philosophical, and even ethical inquiry. This point was misunderstood by most of their opponents, and by most commentators in both political science and IR, who indiscriminately collapse behavioralism and positivism, thereby including the former in any critique of the latter. The behavioralists' aim in fact was to delimit the realm of scientific explanation, and extract those phenomena that could be explained scientifically from the overarching paradigms of philosophical or historical understanding, which precluded the development of a rigorous empirical knowledge of social reality.

Insofar as social processes can be objectivated scientifically, the observer has to operate a separation between what can and cannot be observed and agreed upon through the methods of science. The datum of behavioral science should therefore be amenable to measurement, quantification, testing, and replication, which explains the introduction of mathematics for the purpose of formulating rigorous relationships among clearly defined variables. To the extent that regularities can be discovered, behavioralism aspired not only to explain past or present behavior and processes, but also to predict or anticipate future ones, based on a precise assessment of the weight different variables take in different settings. The development of analytical theories, wherein variables are “operationalized” and related to each other within specific “boundary conditions,” should therefore be validated by empirical testing. Those variables that cannot be tested – either directly or indirectly – cannot be retained by behavioral science.

This epistemic attitude was opposed to two modes of inquiry. The first is the descriptive model of historical investigation, which is necessarily concerned with singular, rather than recurrent, phenomena. This is related to the difference between synchronic and diachronic analysis (Eulau 1969:6). While history constitutes the behavioralist's “laboratory,” it cannot spontaneously generate any explanation unless the comparative method is used to assess the effect of changed historical conditions on the behavior of individuals or social groups. Comparison, in turn, requires the identification of both constants (parameters) and variables, so that it becomes possible to “measure” variations and say something meaningful about what makes different social systems evolve and how change operates.

The second mode of inquiry behavioralism rejected is that which aims for “transcendental truths” and characterizes philosophical, normative, and ethical discourse. More specifically, it intended to extract political science from the speculative, ahistorical, and universalizing narratives of philosophy, which does not allow for “intersubjective validation” of knowledge of the social world (Eulau 1969:11). It is this specific aspect of behavioralism that most radically alienated “traditional” scholars such as Leo Strauss, who considered that behavioralism (identified as positivism) implied “a depreciation of prescientific,” “common sense” knowledge. The aim was no longer to attain an “absolute knowledge of the Why, but only” a “relative knowledge of the How” (Strauss 1969:104, 97).

Heinz Eulau (1969:18–19) provided a good conceptualization of this duality, thereby also highlighting behavioralism's self-awareness of its own limitations:

Perhaps it is best to think of the study of politics as an ever expanding set of concentric circles, with a core that undergoes change very slowly, if at all, and with a periphery that is ill-defined and forever changing. At the core we find the most traditional of approaches.… Here the search is for Truth, with a capital “T,” and for eternal knowledge. At the periphery we encounter the agenda of behavioral science which, unlike any other agenda, knows no limits … because the method of science does not know final knowledge. Here inquiry is undertaken as much to reduce ignorance as to discover truth. What knowledge emerges is assumed to be partial, possibly temporary, contingent on the state of science, and always probabilistic. As science reduces ignorance, it may know what is not the case; it does not arrogate to itself knowledge of the truth. In this sense, behavioral science is without firm boundaries and its agenda is never exhausted.

Within this cognitive framework, behavioralism developed a specific language, and a novel terminology largely imported from other sciences. Behavioralist works characteristically start with very detailed definitions of concepts and variables used, and a clear statement of the research questions investigated, with clearly defined hypotheses and protocols for testing them. The shift from “traditional” to “scientific” research is exemplified in Harold Lasswell and Abraham Kaplan's (1950) Power and Society, which became the first behavioral work to broadly impact the discipline and was famously criticized by Morgenthau (1958:19–20) as a “monstrosity” that reflected a “thorough misunderstanding of the nature of political theory and its relationship to empirical research.” A comparison with Morgenthau's Scientific Man Versus Power Politics (1946) reveals the shift operated by the behavioralists in terms of terminology, background literature, and methodology.

As they developed new bridges connecting them to the rest of the social (and nonsocial) sciences, the behavioralists further alienated those scholars who considered that political science was a discipline whose central object of study – power – distinguished it from all other fields of inquiry. From a behavioralist perspective, the ontological focus on “political behavior,” which is merely one type of “social behavior,” precluded any such intellectual and institutional “autonomy.” Interdisciplinarity was both an epistemic and an ontological necessity, and many behavioralists in fact denied political science the status of academic “discipline.”

Values, Judgment, and the Ethos of Behavioral Science

In retrospect, the behavioralists' extensive discussions of methodological questions were due to the absence of such discussions in “traditional” political science. Methodology was by no means pursued as an end in itself. Although the behavioralists widely contributed to the introduction of the philosophy of knowledge and science in the disciplinary literature, their aim was to improve the concepts and methods of research for the purpose of empirical and practical relevance. For their critics, however, the stress on methodology, methods, and the technicalities of science was shifting attention away from the most important and meaningful questions, most of which appealed to the “judgment” of the scholar rather than to technical standards of inquiry. In the process of “achieving science,” behavioralists thus remained “open to the charge of strenuously avoiding that dangerous subject, politics” (Bay 1969:140) and were even accused of turning “the students of political science into political eunuchs” (McCoy and Playford 1967:9).

This general impression was more specifically related to the central question of the relation of values to knowledge, which was one of the most central points of contention between the behavioralists and their critics. Here again, criticism was addressed to the positivist underpinnings of behavioralism, that is, to the delineation of the epistemic and ontological realm of inquiry within whose boundaries behavioralism consciously limited itself. Eulau summarized behavioralism's axiological stance with respect to three important questions pertaining to values:

First, on the question of whether values can and should be studied by the methods of science, the answer is an unequivocal “yes,” just as the answer is “yes” to the question of whether behavioral science can assess the consequences of alternate policy choices. Second, on the question of whether a “value-free” social science is possible, the answer is “no,” though the exclusion of value considerations in the form of biases that distort scientific inquiry is desirable. And third, on the question of whether behavioral science can arrive at judgments of what is “good” and what is “bad,” the answer is that it cannot – that such judgments are, indeed, the task of ethics as a separate enterprise.

(Eulau 1969:11–12)

The behavioralists had thereby adopted Max Weber's position (see in particular Easton 1953:221), which is based on the “logical heterogeneity” between “statements of facts” and “value-judgments” (Weber 1949a, 1949b). Their central concern was to extract value-judgments from scientific explanation proper, and guarantee that regardless of the context of discovery, the logic of explanation would remain unaffected by personal or collective value preferences (Kaplan 1964). The stress on methodology, wherein value-control became an important standard, was meant to separate science from ideology, and critically raise the scholars' awareness of their own preferences, assumptions, and biases, and of how these polluted the scientific process (Greene 1970). Some behavioralists (such as Dahl) even adopted the strategy of clearly stating their preferences to their readers at the beginning of their analyses. Much of these positions entailed a validation of the American democratic system. The criteria for making such judgments were, however, rarely articulated (Bay 1969:122).

The real disagreement among behavioralists was over the “behavioral scientist's own involvement in the issues of the day,” a classical dilemma for all social scientists, including Weber himself (Weber 2004). Since “there is nothing in the logic of science that compels the scientist to commit himself to one of several conflicting public purposes – or to withhold his commitment,” “commitment is as defensible as its opposite.… In this respect, then, the scientist must come to terms with his own moral conscience. Neither science nor philosophy can legislate his course of action” (Eulau 1969:12).

Disagreement over the scholar's ethos as a social agent was combined with a general tendency to confuse “value neutrality” (cognitive objectivity/impartiality) with “ethical neutrality” (moral disengagement/indifference), two notions that became subsumed under the generic expression “value freedom” (Hamati-Ataya 2011). Much of the debate between the behavioralists and their opponents revolved around this confusing notion. With the rise of the culture of positivism in American academia, the ethos of social and moral “disengagement” prevailed (Gunnell 1993:223), and the more nuanced understanding of the relation of values to knowledge that behavioralists had earlier offered was not only blurred but swept away by the pressing concerns of empirical research. (For a later defense of behavioralism's concern with values, see Searing 1970; Rogers 1977).

A typical example of the confusion between “value neutrality” and “ethical neutrality” is found in Strauss's critique of behavioralism, which also reflects the general impression that behavioralists have by and large taken the discipline toward a disengagement from its most central ethical concerns: “Positivistic social science is ‘value-free’ or ‘ethically neutral’: it is neutral in the conflict between good and evil, however good and evil may be understood … moral obtuseness is the necessary condition for scientific analysis” (Strauss 1969:98). For Strauss, this resulted directly from behavioralism's rejection of common sense and dialectical knowledge: by adopting the “perspective of the scientific observer,” behavioralists had forgotten the equally legitimate and equally necessary “perspective of the citizen” (Strauss 1969:106).

These attacks on the behavioralist ethos were not restricted to the debates among political scientists. Behavioralists from all disciplines were accused of hiding their implicit collusion with power behind the veil of “value freedom.” In the 1960s a general “dissident” movement developed in American social sciences, leading to the establishment of such associations as the Radical Caucus in Sociology, the Sociology Liberation Movement, the Union for Radical Political Economists, and the Caucus for a New Political Science, which considered the “sciencizing” of the discipline as a pursuance of “politics by other means” (Surkin and Wolfe 1970:4). The general impression was that “the rigorous adherence to social science methodology adopted from the natural sciences and its claim to objectivity and value neutrality function as a guise for what is in fact becoming an increasingly ideological, non-objective role for social science knowledge in the service of the dominant institutions in American society” (Surkin 1970:14).

After having succeeded in significantly altering the cognitive attitude of political scientists by stressing the importance of conceptual and methodological rigor, behavioralism was now faced with the dilemmas arising from its flirtation with positivism. In a reflexive awakening that is rare among scholars enjoying the authority and prestige of their dominant paradigm, Easton (1969) himself, then the President of the APSA, offered such a critical assessment, acknowledging the need for moral evaluation and philosophical inquiry, and for a new, “post-behavioralist revolution.”

The Behavioral Revolution is known to have launched IR's second “great debate.” After the founding debate between “realism” and “idealism” over the what-question concerning the discipline's subject matter (Spegele 1996:xv–xvi), the second debate is unanimously viewed as being about “methodology” and the how-question (Vasquez 1983:19; Jackson and Sørensen 2003:45). This view is based on the idea that most behavioralists were realists (Brown and Ainley 2005:33) who “challenged not the picture of the world that the realists had provided but the realist conception of what constitutes an adequate scientific theory and the procedures to ‘verify’ that theory” (Vasquez 1983:23).

The Modeling of International Processes

With the establishment of IR's first “paradigm,” realism, the idea that world politics followed some “objective” laws and trends that the discipline was expected to discover and explain was a familiar and widespread assumption. This made IR “an obvious candidate for the application of the scientific method” (Crawford 2000:30). In their seminal 1950 reader Principles and Problems of International Politics, realists Morgenthau and Kenneth Thompson thus included a text by Nicholas Spykman (1950) that delineated the difference between science and history: “what is true of one apple only is an historical truth; what is true of apples in general is a scientific truth. The historical interest lies in the unique quality of the individual apple, the scientific interest, in the qualities which it has in common with all apples.” For Spykman, the “problem of science is to find out how things work,” and this is precisely what the behavioralists intended to do. Behavioralism was therefore to a large extent a natural development for IR – the pursuance of realism's scientific aspirations. The disagreement between behavioralists and some realists concerned the belief in the unity of science, that is, that the same methodologies and standards applied to both the physical and social sciences. Particularly controversial were the introduction of quantitative analysis and the use of statistics.

Quincy Wright's (1942) A Study of War may be considered the earliest behavioralist work in American IR, and an important achievement for the Chicago School itself (see also Wright 1955). In the following decade, behavioralism imposed its marks in the discipline, with such works as Richard Snyder et al.'s (1954) Decision-Making as an Approach to the Study of International Politics, which became, with James Rosenau's (1966) essay “Pre-Theories and Theories of Foreign Policy” and Margaret and Harold Sprout's (1956) Man–Milieu Relationship Hypotheses in the Context of International Politics, a paradigmatic reference for foreign policy analysis (see also Rosenau 1971). In 1957 were published the two most influential texts, Morton A. Kaplan's System and Process in International Politics, and Karl Deutsch et al.'s Political Community and the North Atlantic Area. These two studies announced the general trend of behavioralist IR scholarship: a primordial concern for the philosophy of science (and knowledge), the use of concepts, theories, and methodologies developed in other sciences, and a reliance on quantitative data and analyses. (Important behavioralist contributions are found in Knorr and Verba 1961; Rosenau 1961.)

Kaplan's System and Process signified the shift operated by behavioralism in IR. Often viewed as a realist for his contribution to the conceptualization of the “balance of power,” he significantly rejected the use of “power” as a meaningful concept for theoretical and empirical analysis, and hence turned his back on all the classical literature of realist IR that borrowed so heavily from political philosophy. Kaplan adopted instead systems theory as developed by W. Ross Ashby in his Design for a Brain (1952), and treated the “international system” as a type of “homeostatic multistable system” that could regulate itself by changing its internal variables to search for better stability. Kaplan envisaged six different types of “international system” in a state of equilibrium, characterized by a different organization of their unit-actors (national and supranational) and a different distribution of capabilities across the system. Two of these had existed (the “balance of power” and “loose bipolar” systems), and the remaining four were properly modeled for the purpose of explanatory and predictive analysis. Richard Rosecrance (1963) would later follow Kaplan's example and identify eight historical models of the international system between 1740 and 1960. “Anarchy” was thus no longer conceived as a monolithic ideal-type for conceptualizing either the international system or international state behavior.

Deutsch also turned his back on realism's legacy and adopted communications theory and cybernetics to analyze “security communities.” Unlike Kaplan, he relied heavily on statistical analyses, which became his central methodology for testing hypotheses. Both Kaplan's and Deutsch's approaches to equilibrium and stability were grounded in the “holistic,” “homeostatic analogy,” whereby equilibrium results from dynamic regulatory processes that operate within the system's functional units. This differed significantly from the “individualist,” “market analogy” that was later used by Kenneth Waltz (1979), wherein equilibrium is the “unintended consequence of rational individual action” (Guzzini 2002:37).

Behavioralism's openness to the other sciences was not restricted to its borrowing of their techniques and cognitive frameworks of inquiry. IR itself became open to specialists from other disciplines, such as economist Kenneth Boulding (1962, 1975), physicist Herman Kahn (1960, 1962, 1965), or mathematician Anatol Rapoport (1963, 1989). John von Neumann and Oskar Morgenstern's (1944) Theory of Games and Economic Behavior became a reference for behavioralist IR scholars, and Nobel Prize winner Thomas Schelling developed Game Theory for the study of strategy and arms control (Schelling 1960, 1966; Schelling and Halperin 1961). By and large, quantitative analysis became a primordial methodology for behavioralist IR, leading to such research projects as the workshop on comparative international systems analysis Kaplan set up at the University of Chicago (Kaplan 1968), J. David Singer and Melvin Small's The Correlates of War Project (1963), which led to a series of handbooks such as The Wages of War, 1816–1965 (1972), or the Dimensionality of Nations Project (see Online Resources).

The focus on quantitativism should, however, not preclude an appreciation of the important developments behavioralism introduced into IR. The behavioralists opened up the discipline to a wide range of theories and paradigms that proved to be very useful, and even necessary, for producing a more sociological discourse on world affairs, drawing on communications theory, the sociology of organizations and administrations, and the like. This introduced the important distinction between “action theories” of foreign policy and “interaction theories” of international systems (Holsti 1971:168). Behavioralism also operated a significant transformation in the way IR scholars perceived the international system and its alleged rational and unitary actors – the states. Graham T. Allison's (1971) Essence of Decision revealed the weight of conflicting administrations in foreign policy decision-making processes; Deutsch's and Kaplan's own works stressed the importance of information as a determining variable for evaluating and explaining states' behavior – and therefore states' “rationality” itself; Kaplan's System and Process and Rosenau's (1969) Linkage Politics contributed to reversing the realists' distinction between the domestic and the international, by showing their mutual influence in the realm of policy-making.

By the 1970s, behavioralism had become the leading paradigm in IR. While Morgenthau still ranked first among IR scholars, he was followed closely by Deutsch and Kaplan, whose System and Process became the second “classic” of American IR after Morgenthau's Politics Among Nations (Finnegan 1972). Like their colleagues in the other social sciences, the behavioralists were, however, under attack on all fronts. As they pushed the scientific agenda farther than their realist predecessors had done, they found themselves in the middle of a debate that aggregated against them not only the more classical realists, but the latter's critics as well. This also coincided with a general awareness that IR had become specifically American in nature, and there was nothing more American than behavioral IR itself.

The “Bull–Kaplan Debate”

IR's “second debate” is the first one to involve a real, albeit difficult, discussion among its protagonists. It also addressed the most fundamental and recurrent questions for the discipline, insofar as it touched upon such issues as the nature of knowledge, science, theory, and explanation; the level-of-analysis and unit-of-analysis problems; the relation to history; the social role and responsibility of science, as well as the ethical dilemmas its practitioners face. Most, if not all, of the issues that would feed IR's following debates and controversies had already been discussed by either the behavioralists or their critics. The debate itself, however, often turned into a dialogue of the deaf. The intellectual origins, background knowledge, and perspectives of its protagonists were too different to permit the adoption of a common language that would sustain the discussion. As a result, there was a great deal of misunderstanding on both sides.

The behavioralists' critics were particularly annoyed by the extensive use of quantitative analyses, which they viewed as reflecting a properly positivist approach to international reality. Stanley Hoffmann (1960:46–7), who had been a disciple of Raymond Aron, and who shared Aron's Weberian, interpretative perspective, saw it as a return of the “old and mistaken [Durkheimian] habit of treating social facts like things,” leading to a “mechanistic” social science wherein “men and societies are reduced to communication systems, without much concern for the substance of the ‘messages’ these networks carry.” Equally problematic for him was the focus on stability and equilibrium: “since purposes and values other than preservation of the system are left out … the status quo becomes an empirical and normative pivot.” For Hoffmann, Kaplan's systems theory was merely “a huge misstep in the right direction – the direction of systematic empirical analysis” (Hoffmann 1960:40).

It is, however, Hedley Bull's defense of the “classical approach” that disciplinary history remembers the most. The second debate is often referred to as the “Bull–Kaplan debate,” following an exchange between the two authors in World Politics (Bull 1966; Kaplan 1966) that occupies a central place in Knorr and Rosenau's (1972) “second debate” reference volume Contending Approaches to International Politics. This is a symbolic but nonetheless misleading reduction of the overall picture. It is symbolic because it reflects the idea that behavioralism was an American intellectual project whose assumptions and objectives remained incomprehensible beyond the circle of its American practitioners, as Bull himself keenly noted. It is nonetheless misleading because, of all the scholars associated with behavioralism in IR, Kaplan is the one who least fits the profile. Not only did he never use the term “behavioralism” or any of its variations, he also shared with its critics their rejection of positivism as a philosophy of knowledge, pursuing his critique of positivism further than any of its “classical” opponents (see Kaplan 1969, 1971, 2000). This important epistemic stance has, however, been widely ignored in the discipline (with the exception of Spegele 1982; Hamati-Ataya 2010, 2012).

Bull's critique (1966:20–1) was addressed at a wide variety of works representing “the scientific approach” – including Kaplan's, von Neumann and Morgenstern's, Schelling's, Deutsch's, and Richardson's – which all “aspir[e] to a theory of international relations whose propositions are based either upon logical or mathematical proof, or upon strict, empirical procedures of verification.” Against their assumptions and methodologies, Bull defended the “classical approach” to theorizing that “derives from philosophy, history and law, and that is characterized above all by explicit reliance upon the exercise of judgment” and by the assumption “that if we confine ourselves to strict standards of validation and proof there is very little of significance that can be said about international relations.” Bull also made explicit some unspoken reasons that explained British scholars' radical rejection of behavioralism, which many of their American counterparts probably shared but never expressed so bluntly or so honestly. These included “feelings of aesthetic revulsion against [behavioralism's] language and methods, irritation at its sometimes arrogant and preposterous claims, frustration at our inability to grasp its meaning or employ its tools, a priori confidence that as an intellectual enterprise it is bound to fail, and professional insecurity induced by the awful gnawing thought that it might perhaps succeed” (Bull 1966:23).

Some of Bull's main propositions against behavioralist IR were common among the latter's critics. Their main objection concerned its positivist leanings, which promoted scientific methodologies and a “fetish for measurement” at the expense of “the only instruments that are at present available for coming to grips with the substance of the subject,” namely, “intuition” and “wisdom” (Bull 1966:26, 31). For Bull, the scientific approach had added nothing meaningful to the understanding of international relations that could not be, or was not already, revealed by the classical approach. More importantly, by turning their back on history and philosophy, the “scientists” had “deprived themselves of the means of self-criticism” (Bull 1966:37). This particular point would become central two decades later in IR's “third debate” (Lapid 1989) between the next generation of “scientific” IR scholars – the Neorealists – and their Critical critics (see in particular the exchange between Kenneth Waltz (1986) and Richard Ashley (1986) and an exposition of the general problem in Hollis and Smith (1991)).

Morton Kaplan took on the task of responding to Bull's and others' criticisms against the “scientific approach” (Kaplan 1966). His reply is the most incisive counter-attack found in the literature. Kaplan pointed out Bull's tendency to subsume under a general, ill-defined, and misunderstood category a wide range of approaches that differed greatly in terms of logical reasoning, mode of inference, theoretical framework, and level of analysis (Kaplan 1966:12–13). As one of the proponents of the “scientific approach,” Kaplan was better equipped to identify and assess these differences, and his criticism only amplified Bull's acknowledgment of the “traditionalists’” ignorance and incomprehension of what the “scientists” were doing and, more importantly, of what science was and entailed. These comments extended even to the content of these approaches, as Kaplan easily demonstrated that authors like Bull and Hoffmann had either not read, or not understood, the new theoretical imports such as Game Theory (Kaplan 1966:14).

His second line of argumentation addressed the very modes and methods of inquiry that the “traditionalists” claimed as their own, superior tools, namely, historical and philosophical inquiry, and intuition. Whether conscious or not, the implicit result of Kaplan's critique is an “appropriation” of the central “traditionalist” scholarly values, in the form of a tu quoque argument that turned these very values against their own position. Responding to the attack on the scientists' disregard for history, he thus noted that

[t]he vaunted sensitivity to history that the traditionalists claim … is difficult to find. Those traditionalists who have done a significant amount of historical research … confine themselves largely to problems of diplomatic history that are unrelated to their generalizations about international politics … or to more specialized problems that are idiosyncratic. This is not an accident but is a direct product of the lack of articulated theoretical structure in the traditionalist approach. It is ironic that the traditionalists are so sure that they alone are concerned with subject matter that they are unaware of the extent to which those applying the newer approaches are using history as a laboratory for their researches. This development is unprecedented in the discipline and is a direct product of the concern of those using scientific approaches for developing disciplined and articulated theories and propositions that can be investigated empirically.

(Kaplan 1966:15–16)

Kaplan also argued that philosophy was given greater attention by those who pursued “scientific” rather than “traditional” approaches. Although he did not spell it out clearly, he was mainly referring to the philosophy of knowledge and science, rather than to the political philosophy that “traditionalists” such as Bull were keen on preserving. His criticism, which focused on the “speculative” dimension of the “traditionalists’” philosophical assumptions and statements, nonetheless encompassed all philosophical inquiry:

The traditionalists talk as if the newer methods have excluded philosophy as a tool for the analysis of international politics. Unfortunately few of them … have demonstrated any disciplined knowledge of philosophy; and many of them use the word as if it were a synonym for undisciplined speculation. There are many profound questions that in some senses are genuinely philosophical; the systems approach, among others, is related to a number of philosophical assumptions.… There are, moreover, some important mistakes that ought to be avoided. Political theory ought not to be called philosophy merely because it is formulated by a man who is otherwise a philosopher unless the ideas have a genuine philosophical grounding. If the ideas are merely empirical propositions, as in the case of most philosophical statements used by traditionalists, they stand on the same footing as other empirical propositions.… Even if some matters of concern to international politics are profoundly philosophical, not all are. It is essential … to address the proper methods to the proper questions and not to make global statements about international politics, as do the traditionalists, which assume the relevance of the same melange of methods regardless of the type of question.

(Kaplan 1966:18–19; for Kaplan's philosophical writings, see Kaplan 1969, 1971, 1976a, 1976b, 1989, 1992, 2000, 2006)

Most ironic perhaps was Kaplan's “scientific” treatment of the notion of human “intuition,” which he extracted from the romanticized narrative of the “traditionalists” by reminding them that “intuition” itself was an object of science, that its intervention in the cognitive process could only be understood by applying the methods of science, and that it was actually being studied by precisely those scientific approaches that the “traditionalists” neither understood nor wanted to understand (Kaplan 1966:3–5).

Kaplan's third line of argumentation addressed the rationale and methodology of the “scientific approach,” whose objective is to produce statements that can be subjected to empirical validation, rather than speculative generalizations. Science is a process of trial and error wherein theories and models are used to test hypothetical propositions. The content of these theories should therefore not be confused with reality itself. And if the attempt to construct models is not made, knowledge remains based on speculations that, however attractive, inherently logical, or intuitively correct, cannot permit the advancement of knowledge and therefore of appropriate social action. That the “traditionalists” should be appalled by the mere attempt to test some propositions about the social world could, according to Kaplan, only be explained by their misunderstanding of the scientific endeavor itself: “The traditionalists mistake explicitly heuristic models for dogmatic assertions. They mistake assertions about deductions within the framework of a model for statements about the open world of history” (Kaplan 1966:20). This disjunction between the respective views of the proponents of “science” and of “tradition” provides a good analytical grid for assessing much of the discussion, confusion, and controversy that surround IR's “second debate.”

Behavioralism in a Post-Behavioralist Era

Some scholars have recently called for a revival of behavioral IR as a subfield concerned with the explanation of the behavior of leaders, rather than states, thereby refocusing behavioralism on the individual as a unit of analysis, and on the underlying processes that account for political judgment and decisions (Mintz 2005, 2006, 2007; James 2007; Walker 2007). It is too early to say whether such a research program can reclaim behavioralism's place among the leading paradigms of IR, or whether the discipline is ready to welcome such a revival. The historiography of IR shows, indeed, that behavioralism's history, identity, and purpose have somehow been warped in the institutional memory of the discipline, and contemporary IR scholars may be skeptical as to the value of a renewed engagement with a school of thought that textbooks generally depict as a defeated empire. Some concluding remarks are therefore in order.

Behavioralism has undoubtedly contributed to the development of political and international theory by promoting – or restoring – the unity of the social sciences, and more generally, by opening them up to the philosophical problems they share with the physical sciences. In political science and IR, the behavioralists' concern for conceptual and methodological rigor has raised scholars' awareness of the inherent ambiguities, biases, and value-preferences that subtend their intellectual production, as well as their standards for analytical rigor and practical usefulness to the world they attempt to explain, and sometimes reform. Behavioralism, in short, “has made the discipline more self-conscious and self-critical” (Somit and Tanenhaus 1967:190). Self-consciousness, however, is historical and therefore relative. Nowadays, behavioralism is often viewed as belonging to the discipline's least reflexive past. This mainly results from the systematic confusion of behavioralism with positivism, the latter being critiqued for combining the two greatest sins postpositivists could envisage: an epistemic “instrumentalist” “bias towards objective explanation” and a consequent “moral non-cognitivism” that leads to an inevitable “moral scepticism” (Spegele 1996:7; Frost 1996:12–13).

Early behavioralists were, however, neither oblivious nor indifferent to either the problem of truth or the problem of values. In the current state of the discipline, where the discussion between positivists and postpositivists has reached a dead-end, while postmodernism threatens to make the whole debate about truth, objectivity, and values meaningless, it is worth reconnecting with this generation of pioneers who pondered on the difficulties of conceptualizing the political without losing sight of the dilemmas of science and social action. Putting behavioralism itself aside, as well as the context and stakes that were specific to the socio-institutional moment that saw its emergence, it is the work of some specific scholars such as Easton, Eulau, and Kaplan that is worth rereading today. One might find in their oeuvre a rigorous, responsible, and courageous attempt to improve our understanding of political reality without surrendering to the easier options of either asserting transcendental truths with no concern for their empirical accuracy or impact on human life, or of offering a loosely descriptive account of the world from an uncritical, common-sense perspective. If IR students are willing to free themselves from the “isms” imposed by the culture of disciplinary history and the textbook narratives of “great debates,” a critical and contextual engagement with these great scholars may help them develop a deeper understanding of the recurrent theoretical and philosophical problems they are bound to face as social scientists.


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Links to Digital Materials

Correlates of War Project. At, accessed November 22, 2010. Includes archives of J. David Singer and Melvin Small's original project, with an updated data collection covering different aspects of war and conflict.

EUGene. At, accessed November 22, 2010. D. Scott Bennett and Allan C. Stam's Expected Utility Generation and Data Management Program. Generates and manages data for quantitative analysis of war and international relations.

Paul Hensel's International Relations Data Site. At, accessed November 22, 2010. Provides links to online data resources for IR research.

Center for Systemic Peace. At, accessed November 22, 2010. Quantitative studies and databases on societal and systemic conflicts.

The Centre for the Study of Civil War at the Peace Research Institute Oslo. At, accessed November 22, 2010. Research and data on national, international, and transnational dimensions of civil wars.

Political Database of the Americas. At, accessed November 22, 2010. Comprehensive data collection on the politics and institutions of the Americas.

The Heidelberg Institute for International Conflict Research. At, accessed November 22, 2010. Research and analysis of national and international political conflicts based on the COSIMO (Conflict Simulation Model).

Dimensionality of Nations Project. At, accessed May 2, 2011. Rudolph J. Rummel's project on Dyadic Foreign Conflict Variables 1950–1965, containing data on conflict behavior.