Evolution of direct reciprocity under uncertainty can explain human generosity in one-shot encounters

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 108; no. 32; pp. 13335 - 13340
• Main Authors: Delton, Andrew W, Krasnow, Max M, Cosmides, Leda, Tooby, John
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 09.08.2011; National Acad Sciences
• Subjects: Altruism; Architecture; Biological altruism; Biological Evolution; Biological Sciences; Cognitive architecture; Computer Simulation; Cooperation; Decision making; decision support systems; Ecological modeling; econometric models; Economic models; Economics; Evolution; Game theory; games; Human subjects; Humans; Interpersonal Relations; Models, Biological; Motivation; Psychological aspects; Social interaction; Uncertainty
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1102131108

Are humans too generous? The discovery that subjects choose to incur costs to allocate benefits to others in anonymous, one-shot economic games has posed an unsolved challenge to models of economic and evolutionary rationality. Using agent-based simulations, we show that such generosity is the necessary byproduct of selection on decision systems for regulating dyadic reciprocity under conditions of uncertainty. In deciding whether to engage in dyadic reciprocity, these systems must balance (i) the costs of mistaking a one-shot interaction for a repeated interaction (hence, risking a single chance of being exploited) with (ii) the far greater costs of mistaking a repeated interaction for a one-shot interaction (thereby precluding benefits from multiple future cooperative interactions). This asymmetry builds organisms naturally selected to cooperate even when exposed to cues that they are in one-shot interactions.