Driving Forces Behind Informal Sanctions
通过合作博弈实验，发现合作者主要惩罚背叛者，而背叛者也会恶意惩罚合作者；当惩罚无法改变收益差距时，恶意惩罚消失，但合作者反而增加惩罚投入。研究区分了不同公平理论，指出报复（伤害不公行为者）是公平驱动非正式制裁的最重要动机。
This paper investigates the driving forces behind informal sanctions in cooperation games and the extent to which theories of fairness and reciprocity capture these forces. We find that cooperators' punishment is almost exclusively targeted toward the defectors, but the latter also impose a considerable amount of spiteful punishment on the cooperators. However, spiteful punishment vanishes if the punishers can no longer affect the payoff differences between themselves and the punished individual, whereas the cooperators even increase the resources devoted to punishment in this case. Our data also discriminate between different fairness principles. Fairness theories that are based on the assumption that players compare their own payoff to the group's average or the group's total payoff cannot explain the fact that cooperators target their punishment at the defectors. Fairness theories that assume that players aim to minimize payoff inequalities cannot explain the fact that cooperators punish defectors even if payoff inequalities cannot be reduced. Therefore, retaliation, i.e., the desire to harm those who committed unfair acts, seems to be the most important motive behind fairness-driven informal sanctions. Copyright The Econometric Society 2005.