Rise and Decline of Social Capital Excess Co-operation in the One-Shot Prisoner's Dilemma Game

In order to explain excess co-operation in the one-shot prisoner's dilemma game, we first question the standard assumption of stable and selfish preferences by introducing the concept of social capital. This analysis leads to a model that explains excess co-operation through an accumulation of social capital. We allow preferences and norms to change over time and hence endogenise them. Our results depend on individuals being able to acquire enough information to allow them to ascertain the social norm that fellow individuals subscribe to. However, our results do not depend on any assumptions about group size and no ostracism is required to generate co-operation. Our model gives three hypotheses about the emergence and stability of social capital and co-operation in society. First, neither unconditional cooperation nor universal defection is stable; second, for co-operation to be stable some individuals must be reciprocal in nature; third, we identify a 'rise and decline of social capital' which gives a cyclical pattern of co-operation in society. These findings may form the basis for future theoretical and empirical research. JEL classification: A12, C71, D23, D60, D70, Z13.