New Mechanism for Sustaining Reputation-Based Cooperation Revealed

An international research team including iTHEMS Team Director Yohsuke Murase has theoretically uncovered a new mechanism that enables the evolution of reputation-based cooperation.

In human societies, “indirect reciprocity,” in which people decide whether to cooperate with others based on their reputations, is considered an important mechanism for sustaining cooperation. However, previous studies have shown that maintaining cooperation becomes difficult when individuals hold different assessments of the same person.

In this study, the researchers introduced a mechanism called “dual reputation updating,” in which reputations are updated based not only on whether a person cooperates with others, but also on whether that person receives cooperation from others. Through mathematical analysis and computer simulations, they demonstrated that this simple extension reduces disagreements in reputation and substantially enhances the maintenance of cooperation.

These findings are expected to deepen our understanding of how cooperation emerges and is sustained through reputation, while also providing new insights into collective behaviors in real-world societies, including conformity, cooperation, and exclusion.

The findings are scheduled to be published in the Proceedings of the National Academy of Sciences (PNAS) on August 28, 2026.