Editor's Summary

1 January 2009

Reasons to be nice

In human societies, altruistic behaviour can evolve when those who fail to co-operate acquire a bad reputation. But how far is it sensible to go on punishing those who don't cooperate, as punishment incurs a cost for both the punisher and the punished? Ohtsuki et al. explore the circumstances under which punishment is favoured using a game theory model in which all individuals observe the interactions between others and assess their reputation according to various social norms. They find that costly punishment can facilitate the evolution of cooperation, but only under a narrow set of parameters. As indirect reciprocity evolves to become more effective, costly punishment is rendered inefficient.

News and ViewsGame theory: How to treat those of ill repute

A much-needed theoretical analysis deals with whether the principle known as 'costly punishment' helps to maintain cooperation in human society. It will prompt a fresh wave of experiments and theory.

Bettina Rockenbach & Manfred Milinski


LetterIndirect reciprocity provides only a narrow margin of efficiency for costly punishment

Hisashi Ohtsuki, Yoh Iwasa & Martin A. Nowak