Evolution of cooperation under pure institutional reward and punishment in collective-risk social dilemma games

Avoiding free-riding in collective actions aimed at achieving collective target is challenging. Research using collective-risk social dilemma games shows that rewards and punishments can mitigate this issue. However, these studies typically assume that the individuals enforcing these incentives also incur the costs of cooperation and implementing the incentives, making the approach costly and inefficient. Here, we introduce pure institutional reward and punishment strategies into collective-risk social dilemma games, where individuals implementing incentives do not bear the costs of cooperation, to investigate their effects on the evolution of cooperation. We find that the introduction of pure reward strategy can promote the stable coexistence of cooperators and free riders within the population. In contrast, the introduction of pure punishment strategies can lead to more diverse dynamics, including monostable, bistable, tristable, and even quadristable outcomes. Our findings highlight the superiority of pure punishment strategies over pure reward strategies in curbing free-rider behavior.