Selfish learning is more important than fair-minded conditional cooperation in public-goods games

Why does human cooperation often unravel in economic experiments despite a promising start? Previous studies have interpreted the decline as the reaction of disappointed cooperators retaliating in response to lesser cooperators (conditional cooperation). This interpretation has been considered evidence of a uniquely human form of cooperation, motivated by altruistic concerns for fairness and requiring special evolutionary explanations. However, experiments have typically shown individuals information about both their personal payoff and information about the decisions of their groupmates (social information). Showing both confounds explanations based on conditional cooperation with explanations based on individuals learning how to better play the game. Here we experimentally decouple these two forms of information, and thus these two learning processes, in public goods games involving 616 Swiss university participants. We find that payoff information leads to a greater decline, supporting a payoff-based learning hypothesis. In contrast, social information has small or negligible effect, contradicting the conditional cooperation hypothesis. We also find widespread evidence of both confusion and selfish motives, suggesting that human cooperation is maybe not so unique after all.