We consider the formation and long-run stability of cooperative groups in a social dilemma situation where the pursuit of individual interests conicts with the maximization of social welfare. The adaptive play model of Young (1993) is applied to a group formation game where voluntary...

People cooperate more in one-shot interactions than can be explained by standard textbook preferences. We discuss a set of non-standard preferences that can accommodate such behavior. They are social, in the sense of incorporating the payoffs of other persons; they are also norm-based, in the...