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Altruistic punishment in humans


Human cooperation is an evolutionary puzzle. Unlike other creatures, people frequently cooperate with genetically unrelated strangers, often in large groups, with people they will never meet again, and when reputation gains are small or absent. These patterns of cooperation cannot be explained by the nepotistic motives associated with the evolutionary theory of kin selection and the selfish motives associated with signalling theory or the theory of reciprocal altruism. Here we show experimentally that the altruistic punishment of defectors is a key motive for the explanation of cooperation. Altruistic punishment means that individuals punish, although the punishment is costly for them and yields no material gain. We show that cooperation flourishes if altruistic punishment is possible, and breaks down if it is ruled out. The evidence indicates that negative emotions towards defectors are the proximate mechanism behind altruistic punishment. These results suggest that future study of the evolution of human cooperation should include a strong focus on explaining altruistic punishment.

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Figure 1: Mean expenditure on punishment during different time intervals as a function of the deviation of the cooperation of the punished group member from the mean cooperation of the other members.
Figure 2: Time trend of mean cooperation together with the 95% confidence interval.


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Support by the MacArthur Foundation Network on Economic Environments and the Evolution of Individual Preferences and Social Norms, and the EU-TMR Research Network ENDEAR is gratefully acknowledged. We also thank R. Boyd, A. Falk, U. Fischbacher, H. Gintis and J. Henrich for comments, and M. Näf and D. Reding for research assistance. We are particularly grateful to U. Fischbacher for writing the computer software.

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Correspondence to Ernst Fehr.

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Fehr, E., Gächter, S. Altruistic punishment in humans. Nature 415, 137–140 (2002).

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