Evolution of cooperation in psychological games with costly information

Cooperation is crucial for both biological and social systems. Yet it is not straightforward from the evolutionary perspective, since individuals are tempted to defect for personal interests. In traditional models, it is usually assumed that cooperation is determined only by external behaviours. Individuals, however, are likely to pay extra psychological costs if what they do differs from what they think, and are likely to pay to know what others think. Motivated by these observations, we extend donation games to psychological games by introducing value-behaviour inconsistency, which creates psychological costs such as guiltiness or regret, and information costs, which individuals pay to know the opponent's values. We find that the key for cooperation under weak rationality is the large guiltiness (the psychological cost for an individual with defective behaviour and cooperative internal value); the heterogeneity of information costs governs how cooperation is further enhanced under moderate rationality; and moderate information costs can effectively favour cooperation under strong rationality, which is typically absent in classical donation games. These findings highlight how guiltiness, regret and information costs together shape cooperative behaviour across the rationality intensity. Our work can be insightful for a novel paradigm of cooperation beyond the classical prisoner's dilemma.