Social image concerns promote cooperation more than altruistic punishment

Human cooperation is enigmatic, as organisms are expected, by evolutionary and economic

theory, to act principally in their own interests. However, cooperation requires individuals to

sacrifice resources for each other’s benefit. We conducted a series of novel experiments in a

foraging society where social institutions make the study of social image and punishment

particularly salient. Participants played simple cooperation games where they could punish

non-cooperators, promote a positive social image or do so in combination with one another.

We show that although all these mechanisms raise cooperation above baseline levels, only

when social image alone is at stake do average economic gains rise significantly above

baseline. Punishment, either alone or combined with social image building, yields lower gains.

Individuals’ desire to establish a positive social image thus emerges as a more decisive factor

than punishment in promoting human cooperation.