In this paper I study conditions for the emergence of cooperativebehavior in a dynamic model of population interaction.The model has finitely many individuals located on a circle. The pay-off of each individual is partly based on the (local)interaction with neighbors and partly on (uniform)...

We consider the possibility that cooperation in a prisoner's dilemma is fostered by people's voluntarily enhancement of their own vulnerability. The vulnerability of a player determines the effectiveness of possible punishment by the other. In the "Gradual" mechanism, players may condition their...