The Influence Of Strategy Asymmetry On Cooperative Evolution

Cooperation behavior abound in nature, including microscopic biological behavior and human behavior. Specifically, the cooperative behavior in today’s society can be seen everywhere, and become the foundation of modern civilization, but it is well known that humans are not always selfless to help others, which makes the cooperation can’t be achieved in any conditions. In real life, some groups can achieve cooperation successfully, while other groups can’t, which naturally aroused people’s speculation and speculation about the factors that affect human cooperation. So, studying the evolution process of cooperative behavior and the mechanism of maintaining cooperation system stability become important problems that scholars are trying to solve.The classical theories have been formatted in the study process of the evolution of cooperation, such as Hamilton’s kin selection theory, group selection theory and the theory of "reciprocity". They believe that cooperation strategy will be the dominant strategy of both parties due to the influence of the kinship, reciprocity or group competition. The formation of these theories are based on the idea of equilibrium and symmetry. However, there is a widespread asymmetry phenomenon in real life, it is unreasonable to assume that the condition of participants in the cooperation system is same. Actually, a lot of evidence suggest that participants in the cooperation system have different degree of asymmetry relationship. So, the evolution of cooperative behavior under the asymmetric relations deserves further study.Based on Dreber et al(2008) study, this paper introduce asymmetric strategies into repeated prisoners’ dilemma, and then design strategy asymmetric experiments by changing both sides ‘strategy number in game. Dividing the participants into two groups randomly: one group have cooperation and defection strategy; the other group have cooperation defection and punishment strategy. We randomly matched two participants that come from different groups and let them play games. Through the Mann- Whitney U test and generalized linear model, the study found that the cooperative ratio between strategy asymmetric system and strategy symmetric system has significant difference, and the average cooperation rate of strategy asymmetric system is higher than strategy symmetric system, which shows that strategy asymmetric can promote cooperation. Strategy asymmetric groups tend to use less punishment strategy and use more cooperation strategy compared with the symmetric groups, which shows that strategy asymmetric group have stronger tendency to preserve their sanity. People with strategic disadvantage tend to choose more cooperation than people in a strategic advantage, but his average payoff significantly lower than people in strategic advantage. In addition, through the analysis of the relationship of punishment strategies use and average payoff between strategy symmetric group and strategy asymmetric group, we know that both group show the winner is not to punish.