Researchers from across the social sciences have found consistent deviations from the predictions of the canonical model of self-interest in hundreds of experiments from around the world. This research, however, cannot determine whether the uniformity results from universal patterns of human behavior or from the limited cultural variation available among the university students used in virtually all prior experimental work. To address this, we undertook a cross-cultural study of behavior in ultimatum, public goods, and dictator games in a range of small-scale societies exhibiting a wide variety of economic and cultural conditions. We found, first, that the canonical model – based on self-interest – fails in all of the societies studied. Second, our data reveal substantially more behavioral variability across social groups than has been found in previous research. Third, group-level differences in economic organization and the structure of social interactions explain a substantial portion of the behavioral variation across societies: the higher the degree of market integration and the higher the payoffs to cooperation in everyday life, the greater the level of prosociality expressed in experimental games. Fourth, the available individual-level economic and demographic variables do not consistently explain game behavior, either within or across groups. Fifth, in many cases experimental play appears to reflect the common interactional patterns of everyday life.

Learning to Work Together: In group endeavors, there is often a tension between working for the greater good of the group as a whole versus working for one's own benefit. Sometimes these paths coincide and sometimes they do not; furthermore, the choices made by other group members can influence the calculation of which path to take. A pair of studies now approaches this challenge from experimental and theoretical points of view. In a forest or fishery, harvesting of wood or food needs to take into account the renewable character of the resource, as well as spatial heterogeneity. Janssen et al. (p. 613 ; see the Perspective by Putterman ) show that communication among the group members is key, both to establishing a maintainable rate of harvesting, as well as enforcement via punishment of noncompliers. Boyd et al. (p. 617 ; see the Perspective by Putterman ) develop a model showing that punishment, which is a costly activity, is most effectively levied when implemented with the approval of group members; that is, coordinated punishment works to the benefit of the whole, whereas individual actions do not.

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.

Human characteristics are the product of gene–culture coevolution, which is an evolutionary dynamic involving the interaction of genes and culture over long time periods. Gene–culture coevolution is a special case of niche construction. Gene–culture coevolution is responsible for human other-regarding preferences, a taste for fairness, the capacity to empathize and salience of morality and character virtues.

This article shows that social norms are better explained as correlating devices for a correlated equilibrium of the underlying stage game, rather than Nash equilibria. Whereas the epistemological requirements for rational agents playing Nash equilibria are very stringent and usually implausible, the requirements for a correlated equilibrium amount to the existence of common priors, which we interpret as induced by the cultural system of the society in question. When the correlating device has perfect information, we need in addition only to posit that individuals obey the social norm when it is costless to do so. When the correlating device has incomplete information, the operation of the social norm requires that individuals have a predisposition to follow the norm even when this is costly. The latter case explains why social norms are associated with other-regarding preferences and provides a basis for analyzing honesty and corruption.