| Abstract 摘要 | The existence of cooperation demands explanation since cooperation is costly to the actor while cooperation is beneficial to the receiver. In repeated interactions, when players adopt the strategy "If you cooperate, then I cooperate. If you defect, then I defect.", the evolution of cooperation is possible. And this is a major mechanism which is called direct reciprocity. Direct reciprocity is based on the assumption that players can use the information about the opponent's behavior; however, the information about the opponent's behavior is sometimes imperfect. And it is not obvious what behavior is most likely to evolve in the case wherein information about the opponent is absent.
Here, I consider the game in which there are two strategies; one is conditional cooperators and the other is unconditional defectors in a repeated prisoner's dilemma. And by analyzing evolutionarily stable strategy (ESS) analysis, I have revealed that the strategy with stubbornness which behaves "If I cooperate in the last move, then I cooperate also in the next round. If I defect in the last move, then I defect also in the next round." in the case wherein information about the opponent's behavior is absent, has the loosest ESS condition. This indicates that the evolution of stubbornness is favored by natural selection. I also would like to discuss the relationship between this study and studies on win-stay, lose-shift (i.e., Wang, Xu, & Zhou, 2014). |
