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.
Max Krasnow is a postdoctoral scholar at the University of California at Santa Barbara’s Center for Evolutionary Psychology. Max’s research focuses on human sociality and explores topics like the evolution of dyadic and n-party cooperation, the design of human cooperative psychology, the design of human social learning, and the design of human gathering psychology. He has studied how simple ecological structures can select for human-like cooperative traits, and how models of ecologically rational solutions to cooperative adaptive problems well describe actual human cooperative behavior.