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Does Punishment Help Maintain Cooperation?

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Photo by Alberto Cueto via LAist Featured Photos on Flickr

Photo by Alberto Cueto via LAist Featured Photos on Flickr
Humans are, more or less, a cooperative species. But how is cooperation maintained when the potential rewards for being a free-rider are so much greater than the rewards for cooperating? New research by UCLA anthropologist Robert Boyd suggests that cooperation in large groups is maintained by punishment.

Consider a small group of individuals: you and your friends. You all have personal relationships with each other, and therefore a simple "you help me, I'll help you" rule maintains cooperations fairly easily. You help your friends because you do not want to hurt them by not cooperating, and because you might need their help in the future.

But now consider a large group, such as a tribe or village. Many of the mechanisms that support cooperation in the small group are lost. The "free-riders," who stop cooperating, still receive the benefits of large group membership. Free-riders are people who benefit from the group in food sharing and protection, for example, without contributing to hunting or war. Despite this, large groups continue to show evidence of cooperation. But how?

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Boyd and colleagues suggest that cooperation is maintained in large groups by punishment, which reduces the benefit to being a free-rider. Previous models construed punishment and unregulated and uncoordinated. Often, the costs of punishment outweigh the costs incurred from not punishing the free-riders. In these models, it is actually advantageous to NOT punish free-riders.

But Boyd's model more closely matches human behavior: individuals meet and decide whether and how to punish group members who are not cooperating. In this way, the costs of punishment are distributed among many individuals, so punishment remains beneficial.

R. Boyd, H. Gintis, S. Bowles. (2010). Coordinated Punishment of Defectors Sustains Cooperation and Can Proliferate When Rare. Science, 328 (5978): 617. DOI: 10.1126/science.1183665