Abstract: This book is the result of a collaborative effort by eleven anthropologists and six economists, and questions the motives that underlie the ways that humans interact socially, and whether these are the same for all societies, and are part of our nature, or are influenced by our environments. Over the past decade, research in experimental economics has emphatically falsified the textbook representation of Homo economicus, with hundreds of experiments that have suggested that people care not only about their own material payoffs but also about such things as fairness, equity, and reciprocity. However, this research has left fundamental questions unanswered: are such social preferences stable components of human nature; or, are they modulated by economic, social, and cultural environments? Until now, experimental research could not address this question because virtually all subjects had been university students, and while there are cultural differences among student populations throughout the world, these differences are small compared with the full range of human social and cultural environments. A vast amount of ethnographic and historical research suggests that people's motives are influenced by economic, social, and cultural environments, yet such methods can only yield circumstantial evidence about human motives. In combining ethnographic and experimental approaches to fill this gap, this book breaks new ground in reporting the results of a large cross-cultural study aimed at determining the sources of social (non-selfish) preferences that underlie the diversity of human sociality. The same experiments that provided evidence for social preferences among university students were performed in fifteen small-scale societies exhibiting a wide variety of social, economic, and cultural conditions by experienced field researchers who had also done long-term ethnographic field work in these societies. The results, which are given in chs. 4 to 14, demonstrated no society in which experimental behaviour is consistent with the canonical model of self-interest, and showed that variation in behaviour is far greater than previously thought, and that the differences between societies in market integration and the importance of cooperation explain a substantial portion of the variation found (which individual-level economic and demographic variables could not). The results also trace the extent to which experimental play mirrors the patterns of interaction found in everyday life. The book has three introductory chapters that include a succinct but substantive introduction to the use of game theory as an analytical tool, and to its use in the social sciences for the rigorous testing of hypotheses about fundamental aspects of social behaviour outside artificially constructed laboratories, and an overview and summary of the results of the fifteen case studies.

Keywords: anthropology, cooperation, cross-cultural study, cultural differences, cultural environment, economic environment, economic experiments, environment, equity, ethnographic research, ethnography, experimental economics, fairness, game theory, historical research, human sociality, market integration, motivation, reciprocity, self-interest, small-scale societies, social behaviour, social environment