Social dilemmas occur when the pursuit of self-interest by individuals in a group leads to less than optimal collective outcomes for everyone in the group. A critical assumption in the human sciences is that people's choices in such dilemmas are individualistic, selfish, and rational. Hence, cooperation in the support of group welfare will only occur if there are selfish incentives that convert the social dilemma into a nondilemma. In recent years, inclusive fitness theories have lent weight to such traditional views (...) of rational selfishness on Darwinian grounds. To show that cooperation is based on selfish incentives, however, one must provide evidence that people donotcooperatewithoutsuch incentives. In a series of experimental social dilemmas, subjects were instructed to make single, anonymous choices about whether or not to contribute money for a shared “bonus” that would be provided only if enough other people in the group also contributed their money. Noncontributors cited selfish reasons for their choices; contributors did not. If people are allowed to engage in discussion, they will contribute resources at high rates, frequently on irrational grounds, to promote group welfare. These findings are consistent with previous research on ingroup biasing effects that cannot be explained by “economic man” or “selfish gene” theories. An alternative explanation is that sociality was a primary factor shaping the evolution ofHomo sapiens. The cognitive and affective mechanisms underlying such choices evolved under selection pressures on small groups for developing and maintaining group membership and for predicting and controlling the behavior of other group members. This sociality hypothesis organizes previously inexplicable and disparate phenomena in a Darwinian framework and makes novel predictions about human choice. (shrink)

The study of reciprocal altruism, or the exchange of goods and services between individuals, requires attention to both evolutionary explanations and proximate mechanisms. Evolutionary explanations have been debated at length, but far less is known about the proximate mechanisms of reciprocity. Our own research has focused on the immediate causes and contingencies underlying services such as food sharing, grooming, and cooperation in brown capuchin monkeys and chimpanzees. Employing both observational and experimental techniques, we have come to distinguish three types of (...) reciprocity. Symmetry-based reciprocity is cognitively the least complex form, based on symmetries inherent in dyadic relationships (e.g., mutual association, kinship). Attitudinal reciprocity, which is more cognitively complex, is based on the mirroring of social attitudes between partners and is exhibited by both capuchin monkeys and chimpanzees. Finally, calculated reciprocity, the most cognitively advanced form, is based on mental scorekeeping and is found only in humans and possibly chimpanzees. (shrink)

Coordinating behavior is widespread in contexts that include courtship, aggression, and cooperation for shared outcomes. The social significance of cooperative coordination (CC) is usually downplayed by learning theorists, evolutionary biologists, and game theorists in favor of an individual behavior → outcome perspective predicated on maximizing payoffs for all participants. To more closely model CC as it occurs under free-ranging conditions, pairs of rats were rewarded for coordinated shuttling within a shared chamber with unrestricted social interaction. Results show that animals learned (...) to work together with sensitivity to the task and type of partner. Moreover, social interaction and coordination influenced both consumption of the reward solution immediately following a session and preference for cooperation, suggesting that affective states and incentives related to cooperation extend beyond the outcomes obtained. These results support field studies by showing not only how cooperation is performed but also the importance of considering how the behavior of cooperating affects outcomes and preference for cooperating. (shrink)

This paper provides strong evidence challenging the self-interest assumption that dominates the behavioral sciences and much evolutionary thinking. The evidence indicates that many people have a tendency to voluntarily cooperate, if treated fairly, and to punish noncooperators. We call this behavioral propensity “strong reciprocity” and show empirically that it can lead to almost universal cooperation in circumstances in which purely self-interested behavior would cause a complete breakdown of cooperation. In addition, we show that people are willing to punish those who (...) behaved unfairly towards a third person or who defected in a Prisoner’s Dilemma game with a third person. This suggests that strong reciprocity is a powerful device for the enforcement of social norms involving, for example, food sharing or collective action. Strong reciprocity cannot be rationalized as an adaptive trait by the leading evolutionary theories of human cooperation (in other words, kin selection, reciprocal altruism, indirect reciprocity, and costly signaling theory). However, multilevel selection theories of cultural evolution are consistent with strong reciprocity. (shrink)

We describe food transfer patterns among Ache Indians living on a permanent reservation. The social atmosphere at the reservation is characterized by a larger group size, a more predictable diet, and more privacy than the Ache typically experience in the forest while on temporary foraging treks. Although sharing patterns vary by resource type and package size, much of the food available at the reservation is given to members of just a few other families. We find significant positive correlations between amounts (...) transferred among pairs of families, a measure of the "contingency" component required of reciprocal altruism models. These preferred sharing partners are usually close kin. We explore implications of these results in light of predictions from current sharing models. (shrink)

In this paper we examine the merit of bargaining theory, in its economic and ecological forms, as a model for understanding variation in the frequency of participation in cooperative fishing among men of Ifaluk atoll in Micronesia. Two determinants of bargaining power are considered: resource control and a bargainer’s utility gain for his expected share of the negotiated resource. Several hypotheses which relte cultural and life-course parameters to bargaining power are tested against data on the frequency of cooperative sail-fishing participation. (...) Consistent with predictions generated from bargaining theory, we show that (1) age is negatively correlated with cooperative fishing participation, (2) men of highranking clans and men with high levels of education fish less than men of low-ranking clans and less-educated men, (3) men with high expected utility gains from fishing returns fish more than men with low expected utility gains, (4) number of dependents is positively correlated with cooperative fishing participation, and (5) the number of young genetic offspring residing with a man is positively correlated with cooperative fishing participation, whereas the number of genetic offspring more than 13 years old who are residing with a man is negatively correlated with cooperative fishing participation. (shrink)