A Framework for the Unification of the Behavioral Sciences
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BEHAVIORAL AND BRAIN SCIENCES (2007) 30,1–61 Printed in the United States of America DOI: 10.1017/S0140525X07000581 A framework for the unification of the behavioral sciences Herbert Gintis Behavioral Sciences, Santa Fe Institute, Santa Fe, NM 87501; Department of Economics, Central European University, Budapest, H-1051 Hungary [email protected] http://www-unix.oit.umass.edu/gintis Abstract: The various behavioral disciplines model human behavior in distinct and incompatible ways. Yet, recent theoretical and empirical developments have created the conditions for rendering coherent the areas of overlap of the various behavioral disciplines. The analytical tools deployed in this task incorporate core principles from several behavioral disciplines. The proposed framework recognizes evolutionary theory, covering both genetic and cultural evolution, as the integrating principle of behavioral science. Moreover, if decision theory and game theory are broadened to encompass other-regarding preferences, they become capable of modeling all aspects of decision making, including those normally considered “psychological,” “sociological,” or “anthropological.” The mind as a decision-making organ then becomes the organizing principle of psychology. Keywords: behavioral game theory; behavioral science; evolutionary theory; experimental psychology; gene-culture coevolution; rational actor model; socialization 1. Introduction of each discipline. We cannot easily attain this goal at present, however, as the various behavioral disciplines The behavioral sciences encompass economics, biology, currently have incompatible models. Yet, recent theoreti- anthropology, sociology, psychology, and political science, cal and empirical developments have created the con- as well as their subdisciplines, including neuroscience, ditions for rendering coherent the areas of overlap of the archaeology, and paleontology, and to a lesser extent, various behavioral disciplines. The analytical tools such related disciplines as history, legal studies, and philos- deployed in this task incorporate core principles from 1 ophy. These disciplines have many distinct concerns, but several behavioral disciplines.3 each includes a model of individual human behavior. The standard justification for the fragmentation of the These models are not only different, which is to be behavioral disciplines is that each has a model of human expected given their distinct explanatory goals, but also behavior well suited to its particular object of study. incompatible. Nor can this incompatibility be accounted While this is true, where these objects of study overlap, for by the type of causality involved (e.g., ultimate as their models must be compatible. In particular, psychol- opposed to proximate explanations). This situation is well ogy, economics, anthropology, biology, and sociology known but does not appear discomforting to behavioral should have concordant explanations of law-abiding scientists, as there has been virtually no effort to repair behavior, charitable giving, political corruption, voting 2 this condition. In their current state, however, according behavior, and other complex behaviors that do not fit the behavioral sciences the status of true sciences is less nicely within disciplinary boundaries. They do not have than credible. such explanations presently. One of the great triumphs of twentieth-century science This paper sketches a framework for the unification was the seamless integration of physics, chemistry, and of the behavioral sciences. Two major conceptual astronomy, on the basis of a common model of fundamen- categories – evolution and game theory – cover ultimate tal particles and the structure of space-time. Of course, and proximate causality. Under each category are concep- gravity and the other fundamental forces, which operate tual subcategories that relate to overlapping interests of on extremely different energy scales, have yet to be recon- two or more behavioral disciplines. In this target article, ciled; and physicists are often criticized for their seemingly I argue the following points: endless generating of speculative models that might accomplish this reconciliation. But a similar dissatisfaction with analytical incongruence on the part of their prac- 1.1. Evolutionary perspective titioners would serve the behavioral sciences well. This Evolutionary biology underlies all behavioral disciplines paper argues that we now have the analytical and empirical because Homo sapiens is an evolved species whose charac- bases to construct the framework for an integrated beha- teristics are the product of its particular evolutionary vioral science. history. The behavioral sciences all include models of individual human behavior. These models should be compatible. 1.1.1. Gene-culture coevolution. The centrality of culture Indeed, there should be a common underlying model, and complex social organization to the evolutionary success enriched in different ways to meet the particular needs of Homo sapiens implies that fitness in humans will depend # 2007 Cambridge University Press 0140-525x/07 $40.00 1 Gintis: A framework for the unification of the behavioral sciences on the structure of cultural life.4 Because culture is influ- the form not only of new techniques for controlling nature, enced by human genetic propensities, it follows that but also of norms and values that are incorporated into human cognitive, affective, and moral capacities are the individual preference functions through the sociological products of a unique dynamic known as gene-culture coevo- mechanism known as socialization and the psychological lution, in which genes adapt to a fitness landscape of which mechanism known as internalization of norms. Surpris- cultural forms are a critical element, and the resulting ingly, the internalization of norms, which is perhaps the genetic changes lay the basis for further cultural evolution. most singularly characteristic feature of the human mind This coevolutionary process has endowed us with prefer- and central to understanding cooperation and conflict in ences that go beyond the self-regarding concerns empha- human society, is ignored or misrepresented in the other sized in traditional economic and biological theories, and behavioral disciplines, anthropology and social psychology embrace such other-regarding values as a taste for aside. cooperation, fairness, and retribution; the capacity to empathize; and the ability to value such constitutive beha- viors as honesty, hard work, toleration of diversity, and 1.2. Game theory 5 loyalty to one’s reference group. The analysis of living systems includes one concept that does not occur in the nonliving world and that is not ana- 1.1.2. Imitation and conformist transmission. Cultural lytically represented in the natural sciences. This is the transmission generally takes the form of confor- notion of a strategic interaction, in which the behavior of mism – that is, individuals accept the dominant cultural individuals is derived by assuming that each is choosing forms, ostensibly because it is fitness-enhancing to do so a fitness-relevant response to the actions of other individ- (Bandura 1977; Boyd & Richerson 1985; Conlisk 1988; uals. The study of systems in which individuals choose Krueger & Funder 2004). Although adopting the beliefs, fitness-relevant responses and in which such responses techniques, and cultural practices of successful individuals evolve dynamically, is called evolutionary game theory. is a major mechanism of cultural transmission, there is Game theory provides a transdisciplinary conceptual constant cultural mutation, and individuals may adopt basis for analyzing choice in the presence of strategic new cultural forms when those forms appear better to interaction. However, the classical game-theoretic serve their interests (Gintis 1972; 2003b; Henrich 2001). assumption that individuals are self-regarding must be One might expect that the analytical apparatus for under- abandoned except in specific situations (e.g., anonymous standing cultural transmission, including the evolution, market interactions), and many characteristics that classi- diffusion, and extinction of cultural forms, might come cal game theorists have considered logical implications of from sociology or anthropology, the disciplines that focus the principles of rational behavior, including the use of on cultural life; but such is not the case. Both fields treat backward induction, are in fact not implied by rationality. culture in a static manner that belies its dynamic and evol- Reliance on classical game theory has led economists and utionary character. By recognizing the common nature of psychologists to mischaracterize many common human genes and culture as forms of information that are trans- behaviors as irrational. Evolutionary game theory, whose mitted intergenerationally, biology offers an analytical equilibrium concept is that of a stable stationary point of basis for understanding cultural transmission. a dynamical system, must therefore replace classical game theory, which erroneously favors subgame perfec- tion and sequentiality as equilibrium concepts. HERBERT GINTIS is an External Faculty member at the Santa Fe Institute, New Mexico, and Professor of 1.2.1. The brain as a decision-making organ. In any Economics at the Central European University, Buda- organism with a central nervous system, the brain pest, Hungary. He heads a multidisciplinary research evolved because centralized information processing project