Presentation Information

[SS19-02]Indirect reciprocity under opinion synchronization

*Murase Yohsuke1, Christian Hilbe2 (1. RIKEN R-CCS (Japan), 2. Interdisciplinary Transformation University (Austria))

Keywords:

cooperation,indirect reciprocity,social norms

Indirect reciprocity is widely recognized as a key mechanism underlying the remarkable scale of human cooperation. Research in this area suggests that much of human cooperation is shaped by social norms and individuals' incentives to maintain a good reputation. This idea has been formalized through two types of models. Public assessment models assume that all members of a community share a common perception of reputations, while private assessment models allow for disagreements. Both approaches explore the relationship between social norms and cooperation, yet they often yield strikingly different conclusions. Public assessment models suggest that cooperation emerges easily and favors strict norms, whereas private assessment models indicate that cooperation is unstable and that successful norms tend to be more forgiving. In this study, we introduce a unifying model that organizes these contrasting results within a single framework. We demonstrate that the stability of cooperation hinges on a single factor: the degree to which individual opinions are correlated. This correlation is shaped by the group's norms and the structure of social interactions. Notably, we prove that no cooperative norm can be evolutionarily stable when individual opinions are entirely independent. These findings offer new insights into the dynamics of cooperation, conformity, and polarization.