2019 Volume 8 Issue 2 Pages 35-46
Despite extensive studies on the evolution of cooperation in indirect reciprocity, little is known about which social norms are favored in a process of evolution of society. Because most previous studies rely on an assumption which a single norm is shared in all members of society. However, different people often follow different norms, which lead to different opinions of the same person. To address this issue, this paper considers the situation where various norms coexist in society as “a norm ecosystem” and clarify the roles of each norm in this ecosystem. In addition, the effect of the network structure of society on the evolution of the norm has been an unsolved problem. The paper analyzes how the co-evolution process of norms and cooperation is affected by the network structure. The results show that norms that had been considered impossible to achieve cooperation were indispensable for the evolution of cooperation in societies with a high degree of connection. These results indicate that in order to realize a cooperative society, it is necessary to consider not only measures to maintain cooperation but also norms necessary for the evolution of cooperation.
