Panchanathan Karthik, Boyd Robert
Center for Behavior, Evolution, and Culture and Department of Anthropology, University of California, Los Angeles, California 90095, USA.
Nature. 2004 Nov 25;432(7016):499-502. doi: 10.1038/nature02978.
Models of large-scale human cooperation take two forms. 'Indirect reciprocity' occurs when individuals help others in order to uphold a reputation and so be included in future cooperation. In 'collective action', individuals engage in costly behaviour that benefits the group as a whole. Although the evolution of indirect reciprocity is theoretically plausible, there is no consensus about how collective action evolves. Evidence suggests that punishing free riders can maintain cooperation, but why individuals should engage in costly punishment is unclear. Solutions to this 'second-order free rider problem' include meta-punishment, mutation, conformism, signalling and group-selection. The threat of exclusion from indirect reciprocity can sustain collective action in the laboratory. Here, we show that such exclusion is evolutionarily stable, providing an incentive to engage in costly cooperation, while avoiding the second-order free rider problem because punishers can withhold help from free riders without damaging their reputations. However, we also show that such a strategy cannot invade a population in which indirect reciprocity is not linked to collective action, thus leaving unexplained how collective action arises.
大规模人类合作的模式有两种形式。当个体为了维护声誉从而被纳入未来的合作中而帮助他人时，就会发生“间接互惠”。在“集体行动”中，个体从事对整个群体有益但成本高昂的行为。虽然间接互惠的进化在理论上是合理的，但关于集体行动如何进化并没有共识。有证据表明，惩罚搭便车者可以维持合作，但个体为何要进行代价高昂的惩罚尚不清楚。解决这个“二阶搭便车问题”的方法包括元惩罚、突变、从众、信号传递和群体选择。在实验室中，被间接互惠排除在外的威胁可以维持集体行动。在这里，我们表明这种排除在进化上是稳定的，提供了进行代价高昂的合作的动机，同时避免了二阶搭便车问题，因为惩罚者可以不给搭便车者提供帮助而不损害自己的声誉。然而，我们也表明，这样一种策略无法侵入一个间接互惠与集体行动没有联系的群体，因此集体行动如何产生仍无法解释。
