Learning to cooperate in the Iterated Prisoner’s Dilemma by means of social attachments

The Iterated Prisoner’s Dilemma (IPD) has been used as a paradigm for studying the emergence of cooperation among individual agents. Many computer experiments show that cooperation does arise under certain conditions. In particular, the spatial version of the IPD has been used and analyzed to understand the role of local interactions in the emergence and maintenance of cooperation. It is known that individual learning leads players to the Nash equilibrium of the game, which means that cooperation is not selected. Therefore, in this paper we propose that when players have social attachment, learning may lead to a certain rate of cooperation. We perform experiments where agents play the spatial IPD considering social relationships such as belonging to a hierarchy or to coalition. Results show that learners end up cooperating, especially when coalitions emerge.