A norm knockout method on indirect reciprocity to reveal indispensable norms
This addresses the problem of understanding norm dynamics in evolutionary game theory for researchers, but it is incremental as it applies a known genetic engineering concept to a specific domain.
The study tackled the unclear role of diversified norms in the evolution of cooperation under indirect reciprocity, revealing that cooperation fails when specific intolerant norms are removed, with most norms transitioning to tolerant ones after defectors are eliminated.
Although various norms for reciprocity-based cooperation have been suggested that are evolutionarily stable against invasion from free riders, the process of alternation of norms and the role of diversified norms remain unclear in the evolution of cooperation. We clarify the co-evolutionary dynamics of norms and cooperation in indirect reciprocity and also identify the indispensable norms for the evolution of cooperation. Inspired by the gene knockout method, a genetic engineering technique, we developed the norm knockout method and clarified the norms necessary for the establishment of cooperation. The results of numerical investigations revealed that the majority of norms gradually transitioned to tolerant norms after defectors are eliminated by strict norms. Furthermore, no cooperation emerges when specific norms that are intolerant to defectors are knocked out.