This paper explains why people might cooperate playing an infinitely recurring prisoners' dilemma in which they change their partner in every period. After two people have played the prisoners' dilemma there is a possibility for networking. Then, two cooperators who played against each other...

The article suggests a new explanation for cooperation in large, unstructured societies that avoids the restrictions required in most previous attempts. Our explanation deals with the role of internalized norms. Even internalized norms, i.e. norms that alter the perceived utility from acting in...