The role of reputations in the evolution of human cooperation

Abstract

In human societies, cooperation between strangers flourishes despite the risk of being exploited. Correct evaluation of others‟ cooperative intentions aids in selecting partners for profitable interactions. Assessment of intentions can be made by (a) considering individuals‟ reputations gained through observed interactions with others and third-party information (gossip) or (b) interpreting immediate cues such as facial expressions and body language. I empirically investigated the role reputations play in human economic decisions. More specifically, I addressed research questions such as (1) how and why people manage cooperative reputations, (2) what role reputations play in partner choice, (3) whether reputations can stabilize cooperation in groups, (4) whether people have a memory bias for specific reputations and (5) whether the ability to assess trustworthiness in faces relates to mind reading skills known as Theory of Mind (ToM). Student participants were recruited for five experiments, all involving the use of economic games to a greater or lesser extent. Depending on the study, participants either played social dilemma games in groups under various experimental conditions or performed individual tasks e.g. recalled information previously presented in different contexts or assessed photographed faces with regard to their cooperativeness and completed ToM tasks. The results provide evidence for the existence of reputation-based partner choice („competitive altruism‟). Participants strategically invested in reputations and reaped benefits from such investments in the form of profitable interactions with the most desired partners. By varying endowments I demonstrated that resource inequalities affect the way people invest in reputation with low-resource individuals behaving in a relatively more generous way than their high-resource counterparts. Moreover, I showed that cooperation in social dilemmas can be stabilized by introducing reputational incentives in the form of partner choice. My results also suggest that people have a memory bias for information about uncooperative acts which is independent of the cooperativeness of the environment they are exposed to. I found no relationship between the ability to identify cooperative intentions in faces and ToM skills. In summary, by unravelling the mechanisms behind reputational cooperation my thesis sheds light on the reasons for extensive cooperation among strangers observed in humans.