Cooperation in Social Dilemmas: The Role of Punishment and Volunteering

The emergence and maintenance of cooperative behavior that is beneficial to others but costly to the individual represents a major conundrum in evolutionary biology. Punishment represents an efficient mechanism to stabilize and maintain cooperation in social dilemmas and is ubiquitous in animal and human societies - ranging from toxin producing microorganisms to law enforcement institutions - but it remains unresolved how initially rare costly punishment can gain a foothold and spread through the population. In nature, animals and humans often select their interaction partners or adjust their behavior in response to them. In the simplest case they simply refuse to participate in risky enterprises. Such voluntary participation in social dilemmas is an efficient mechanism to prevent deadlocks in states of mutual defection, and thus represents a potent promoter of cooperation that nevertheless fails to stabilize it. However, the combined efforts of punishment and volunteering may change the odds in favor of cooperation. Interestingly, even the combined efforts fail in infinite populations, but provide a most efficient mechanism to stabilize cooperation (and punishment) in the stochastic dynamics of finite populations under mutation and selection. Thus the freedom to withdraw leads to prosocial coercion. This implements Hardin's principle: mutual coercion mutually (and voluntarily) agreed upon.