The role of punishments in promoting cooperation is an important issue. We incorporate costly punishments into the snowdrift game (SG) by introducing a third punishing (P) character, and study the effects. The punishers, who carry basically a cooperative (C) character, are willing to pay a cost...

The N-person evolutionary snowdrift game (NESG) is generalized to study the effects of the additional benefit to all agents in a competing group of size N resulting from an earlier completion of a task when more agents are willing to share the work. Following replicator dynamics, an equation...