Collective action and the detrimental side of punishment.

Cooperative behavior is the subject of intense study in a wide range of scientific fields, yet its evolutionary origins remain largely unexplained. A leading explanation of cooperation is the mechanism of altruistic punishment, where individuals pay to punish others but receive no material benefit in return. Experiments have shown such punishment can induce cooperative outcomes in social dilemmas, though sometimes at the cost of reduced social welfare. However, experiments typically examine the effects of punishing low contributors without allowing others in the environment to respond. Thus, the full ramifications of punishment may not be well understood. Here, I use evolutionary simulations of agents playing a continuous prisoners dilemma to study behavior subsequent to an act of punishment, and how that subsequent behavior affects the efficiency of payoffs. Different network configurations are used to better understand the relative effects of social structure and individual strategies. Results show that when agents can either retaliate against their punisher, or punish those who ignore cheaters, the cooperative effects of punishment are reduced or eliminated. The magnitude of this effect is dependent on the density of the network in which the population is embedded. Overall, results suggest that a better understanding of the aftereffects of punishment is needed to assess the relationship between punishment and cooperative outcomes.