Coevolution of social norms and cooperation in public and private situations

Abstract

Cooperation in human society is sustained by reputation. A person’s reputation is determined by the people who observe its behavior, but it is rarely observed in private situations. Thus, people can be cooperative in public situations but uncooperative in private situations. A previous experiment shows that people give a lower reputation for such a person than a consistently uncooperative person regardless of public and private situations. However, the reason is unclear. Here, we investigated how cooperation and the reputational mechanism co-evolve on a condition that two types of interaction (public and private) exist. Evolutionary simulations show that the social norm, which gives a high reputation for consistent behavior in both interactions, evolves and promotes cooperation when both interactions happen enough, and the risk that behaviors in private interactions are observed exists but is low.