Conformism and Cooperation in a Local Interaction Model

We present and analyze a local interaction model where agents play a bilateral prisoner's dilemma game with their neighbors. Agents learn about behavior through payoff-biased imitation of their interaction neighbors (and possibly some agents beyond this set). We find that the [Eshel, I., L. Samuelson and A. Shaked, 1998, Altruists, Egoists and Hooligans in a Local Interaction Model, Am. Econ. Rev 88] result that polymorphic states are stochastically stable in such a setting is not robust. In particular whenever agents use information also of some agents beyond their interaction neighbors the unique stable outcome is one where everyone chooses defection. Introducing a sufficiently strong conformist bias into the imitation process we find that full cooperation always emerges. Conformism is thus identified as a new mechanism that can stabilize cooperation.