| How social is possible, which is the basic issue of social science; how cooperation is possible, which is the fundamental question of behavioral science. Cooperation, which is widespread in social life, is the basis of human civilized society. However, why the altruism behavior can exist from an evolutionary perspective, is actually one unsolved mystery. Individuals' migration in the social network plays an important role in the answering this question. The migration of agents is an important method for the formation of co-evolution and cooperative clumps. Meanwhile, the method of the computational economics provides a powerful tool for explaining the emergence of cooperation. On the basis of this context, this thesis uses computational method to study the influence of different migration mechanism on the evolution of cooperation.Evolutionary game theory as a theoretical tool and computational economics based agent as a research method are used to discuss the evolution of cooperation in the spatial Prisoner's dilemma game from the view of the network structure and migration. To be more specific, we analysis the effect of the migration mechanism based on "to be close to the gentleman, to be away from the villain", heterogeneous risk preference and social welfare respectively, on the evolution of cooperation in the evolutionary game model. How the migration in the social network affects the cooperative behaviors, which has been explained in the following studies.First, we study the effect of the "to be close to the gentleman, to be away from the villain" on the evolution of cooperation. The meaning of the "to be close to the gentleman" is that agents cannot move when all of the neighbors are cooperators; otherwise, agents move with a probability which is the behavior for "to be away from the villain". we establish a migration model based on payoff and cost to discuss the effect of the migration cost on the cooperation level. The results show that the moving mechanism based on "to be close to the gentleman, to be away from the villain" improves the level of cooperation in a wide parameter space, which provides new ideas for understanding the cooperative behaviors in the society. The spatial state diagrams under different conditions have been shown to provide an intuitive understanding of the emergency for the cooperative clusters. Besides, we study the evolution of cooperation in the small world network in order to explore the effectiveness of the migration mechanism in other network structures. The results show that the migration mechanism promotes the cooperation in the small world network.Next, we study the effect of the migration based on risk preference on the evolution of cooperation in the spatial Prisoner's dilemma game. Previous studies had not considered the risk preference or supposed the agents are risk neutral. However, the risk preference is heterogeneous in real life. So, we establish a migration model based on the risk preference and simulate the dynamic evolution process by using the computational economics. Moreover, we distinguish homogeneous risk preference influence on the cooperation from heterogeneous one. When we assume the homogeneity of risk preference, the results show that the risk aversion population is not beneficial for the emergence of cooperators; when we suppose the heterogeneity of risk preference; the results show that the heterogeneity of risk preference realizes the co-evolution of cooperative phenomenon and network structure under some parameters. Moreover, the level of cooperation reduces with the degrees of heterogeneity increasing. Meanwhile, we study the effect of the migration cost, the temptation to defect and population density on the cooperation level, respectively.Last, in order to study the relation between social welfare based migration and the evolution of cooperation, we consider an evolutionary Prisoner's dilemma game(PDG) where an individual's migration depends on different social welfare functions. We introduce three important social welfare functions (SWFs) commonly studied in social science:Utilitarian SWF, Bernoulli-Nash SWF and Rawlsian SWF. We find that social welfare based migration can promote cooperation under a wide range of parameter values. The cooperation level under Utilitarian SWF and Rawlsian SWF is higher than no migration, but Bernoulli-Nash SWF inhibits the emergency of cooperation compared with the no migration. The consideration of social welfare is a reflection of other-regarding of individuals, therefore, our work should be helpful to understand the evolution of human cooperation and bridge the chasm between the studies of social preferences and social cooperation. We can also provide some references for policy makers. |
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