Punishment motivated by fairness, not revenge

Researchers at UCL and Harvard have found that we punish cheats only when they end up better off than us, in a study that challenges the notion that punishment is motivated by revenge. Published today in the journal Biology Letters , the research shows that victims of cheating compare their own payoffs with those of partners when making punishment decisions. "Punishment is a costly behaviour which is often aimed at individuals that cheat during social interactions," said Nichola Raihani (UCL Genetics, Evolution and Environment), lead author of the study. "Imagine a thief steals £10 from you. Would you punish him because he cost you £10, or would you only punish if the thief ended up £10 richer than you?"  Although punishers make an initial investment to harm cheats, the investment may be repaid if the cheat behaves more cooperatively in future interactions. Playing an important role in the maintenance of cooperation in humans, it is this relationship between punishment and cooperation - and the motives that underpin it - that Raihani and colleagues aim to clarify. To find out more about the underlying motivations of human punishment, the team devised an experiment to see whether human punishment is triggered by a desire to reciprocate losses or by an aversion to unequal outcomes.