Grupo Interdisciplinar de Sistemas Complejos, Departamento de Matemáticas, Universidad Carlos III de Madrid, 28911 Leganés, Spain.
Sci Rep. 2012;2:638. doi: 10.1038/srep00638. Epub 2012 Sep 7.
Reciprocity or conditional cooperation is one of the most prominent mechanisms proposed to explain the emergence of cooperation in social dilemmas. Recent experimental findings on networked games suggest that conditional cooperation may also depend on the previous action of the player. We here report on experiments on iterated, multi-player Prisoner's dilemma, on groups of 2 to 5 people. We confirm the dependence on the previous step and that memory effects for earlier periods are not significant. We show that the behavior of subjects in pairwise dilemmas is qualitatively different from the cases with more players; After an initial decay, cooperation increases significantly reaching values above 80%. The strategy of the players is rather universal as far as their willingness to reciprocate cooperation is concerned, whereas there is much diversity in their initial propensity to cooperate. Our results indicate that, for cooperation to emerge and thrive, three is a crowd.
互惠或条件合作是解释社会困境中合作出现的最突出机制之一。最近关于网络博弈的实验结果表明，条件合作也可能取决于参与者的先前行为。我们在这里报告了关于迭代、多人囚徒困境的实验，参与者为 2 到 5 人一组。我们证实了对前一步的依赖性，并且早期阶段的记忆效应并不显著。我们表明，在双人困境中，主体的行为与更多参与者的情况有很大不同；在初始衰减之后，合作显著增加，达到 80%以上。只要参与者愿意回报合作，他们的策略就相当普遍，而他们最初合作的倾向则存在很大差异。我们的结果表明，要想合作出现并蓬勃发展，三人成众。
