Why people punish in public goods games , and on whom punishment is most effective : Conventional wisdoms reconsidered

Theoretical and experimental research underscores the role of punishment in the evolution of cooperation between humans. Experiments using the public goods game have repeatedly shown that in cooperative social environments, punishment makes cooperation flourish, and that withholding punishment makes cooperation collapse. In less cooperative social environments, where antisocial punishment has been detected, punishment was detrimental to cooperation. The success of punishment in enhancing cooperation is explained as deterrence of free riders by cooperative strong reciprocators, who were willing to pay the cost of punishing them, whereas in environments in which punishment diminished cooperation, antisocial punishment was explained as revenge by low cooperators against high cooperators suspected of punishing them in previous rounds. The present paper reconsiders the generality of both explanations. Using data from a novel public good experiment with punishment and from 16 public goods experiments from countries around the world, we report results showing that revenge alone does not drive antisocial punishment of cooperators, and that such punishment is predominantly part of an upward and downward punishment strategy, presumably aimed at punishing those who deviate from the punisher’s aspired cooperation norm. More interestingly, we show that the effect of punishment on the emergence of cooperation is mainly due to contributors increasing their cooperation, more than free riders being deterred. We also show that the anticipation of being punished is more effective in enhancing cooperation than the actual punishment itself, and that the ratio of strong reciprocators in a given social group is a potent predictor of the group’s level of cooperation and success in providing public goods. Keyword: Cooperation, Punishment, Antisocial Punishment, Public Goods, Strong Reciprocity