[A test of the strong reciprocity model: relationship between cooperation and punishment].

The strong reciprocity model of human cooperation (SRM) argues that strong reciprocators, who cooperate with others and punish non-cooperators, sustain within-group cooperation. However, the assumption that altruism and punishment are products of the same psychological mechanism of strong reciprocity has not been fully verified. Second-party punishment, for example as measured through rejection of unfair offers in the ultimatum game, has been demonstrated to have no relationship with cooperation in the prisoner's dilemma and other games. In this study, we tested the assumption of the SRM by comparing the participants' levels of cooperation in the prisoner's dilemma game and their inclination for punishment in a third-party punishment game. Non-student recruited from the general population (N = 182) participated in the study. The results show a weak but positive correlation between cooperation and third-party punishment, which is consistent with the SRM model.