The Evolution Of Cooperation Considering Conformity Effect Under Bounded Rationality In Spatial Public Goods Game

Cooperation exists widely in the ecosystem,which contradicts with Darwin’s theory of natural selection.Evolutionary game theory seems to be a powerful theoretical framework to explain the emergence of cooperative behavior among selfish individuals in social dilemmas,and public goods game is regarded as a typical paradigm for studying interactions of multi-agents.Conformity behavior appears ordinary for boundedly rational agents,which is widespread in all aspects of social life.For example,in donations,in a political voting,in an ecological protection and in consumer behavior and so on,conformity behavior exerts a great impact.In addition,conformity behavior is crucial in humans’ social learning.Therefore,from the perspective of social learning,this thesis explores the impact of the conformity imitation in social learning for agents on the evolution of cooperation in a structured population.The main works of this thesis is as follows:Firstly,an alternative learning mechanism based on probability in social learning is proposed,which is driven by conformity and reputation.Differing from the typical strategy-updating mechanism where one of the neighbors is randomly selected and imitated with an accumulated probability,we assume that conformity imitation or reputation-influenced imitation is adopted by each agent according to a certain probability in this thesis.The simulation results show that social learning driven by conformity and reputation can greatly promote cooperation,which means that the conformity effect and reputation mechanism exert a synergy.On the contrary,any single learning mechanism has no obvious impact on cooperation enhancement.Besides,the micro mechanism of the synergy between conformity effect and reputation mechanism is studied.It refers that reputation mechanism works in a part of population when enhancement factor is beneficial to induce more cooperators,then the conformists in another part could join them easily,which enlarges the cluster of cooperators and high reputations constantly,enhancing the proportion and fitness of them and further strengthening the role of reputation mechanism.Secondly,based on an existing conformity imitation rule,we propose a conformity imitation rule under different group scales among a structured population during the evolutionary process.Additionally,considering the characteristics of conformists,two comparative models are set,one is that the conformists are randomly selected,and the other is that the conformists are selected from those with the lowest payoff in a group.Via comparative analysis,it is found that the impact on the evolution of cooperation of the two models mainly differs in the following: Firstly,under different proportions of conformists,a larger group scale of conformity imitation impedes cooperation.And a moderately larger group scale can promote cooperation,otherwise it exerts a negative impact on cooperation.Secondly,under smaller enhancement factors,the larger proportion of conformists with low payoffs is,the more obvious the cooperation effect is;On the contrary,the density of cooperation drops with the increase of randomly-chosen conformists.Finally,there is also the similarity,which elaborates that a most small group scale promotes cooperation to the greatest extent under larger enhancement factors in social learning.Finally,rational conformity based on payoff satisfaction in social learning in public goods game is considered.Two types of agents and two corresponding social learning rules are introduced in SPGG.One is link-type agents based on the rational conformity learning rule,whose strategies are independent in different groups.The other is node-type agents based on the Fermi learning rule,whose strategies are the same in different groups.Rational conformity behavior signifies that conformity only occurs when individuals are unsatisfied with their payoffs.Through simulation experiments,we find that cooperation can be induced constantly with a large proportion of link-type agents,in which situation rational conformity behavior in social learning is conducive to the emergence of cooperation.We further find that the independent strategies of link-type agents favor reciprocity to be enhanced among cooperative groups and the extended imitation range is beneficial to distinguish cooperative groups which also improves cooperation.Moreover,an appropriate payoff threshold is favorable to induce a positive correlation between payoffs and contributions,and thus a more reasonable distribution of payoffs and strategies.Meanwhile,the payoff threshold in the rational conformity learning rule is also contributed to diminishing the spread of defective behavior for those defectors with outstandingly high payoffs.These results expand our comprehension of individuals’ conformity behavior in social learning and its effect on cooperation in social dilemmas.In this thesis,three types of conformity imitation rules are set in SPGG,and we elaborate on the relation of the conformity effect and the cooperative evolution from three perspectives.These results avail to enrich cooperative mechanisms and the researches of social learning related to conformity imitation in evolutionary game theory.