By Juan Li, Yi Liu, Zhen Wang, Haoxiang Xia

This study explores why individuals are willing to bear the cost of punishing defectors in cooperative settings, offering a new explanation: the punisher's motivation is egoistic rather than altruistic. Egoistic punishment, aimed at recovering personal losses rather than enforcing group norms, proves to be more effective in promoting cooperation across a variety of conditions. Using spatial public goods game models and both peer- and pool-punishment mechanisms, the research shows egoistic punishers can outcompete altruistic ones in promoting collective cooperation. This dynamic holds across different population structures and strategy-update rules. Particularly in pool-punishment settings, egoistic punishment functions better in high-cost, low-fine scenarios, revealing that self-interested motivations may provide a more robust foundation for sustaining public goods. By demonstrating that fairness perceived through self-interest can lead to broader cooperative outcomes, the study challenges conventional assumptions about the purely moral basis of punishment.

(Scientific Reports, 2021, Volume 11, Article Number: 6584, 13p.)