A social dilemma is a situation in which mutual cooperation is expected, but it is difficult for individuals who choose non-cooperation to always gain, so mutual cooperation is difficult to achieve.The social dilemma has the basic mechanism of many social problems, and exploring the feasibility of a cooperative society in a competitive environment has become an important issue in modern society.

　This time, the research group analyzed what kind of strategy survives and realizes a cooperative society when introducing a new behavior of non-participation in the game into the basic model of the social dilemma called "Prisoner's Dilemma".Previous research was only an analysis of a combination of simple strategies, but this time, we have developed a visualization method for complex simulation results and succeeded in adaptive strategic analysis in an environment where about 2 strategies coexist.

　As a result, in a sequential game such as shogi, the strategy of "escape if betrayed and cooperate if the opponent escapes" becomes dominant and a cooperative society is realized.On the other hand, in simultaneous turn games such as rock-paper-scissors, it turns out that the strategy of "betrayal when exploited or exploited, and turning to cooperation when not" becomes dominant.Both strategies can basically maintain a cooperative society because they continue to cooperate when they cooperate with each other, but there is a big difference in the process of repairing relationships when the cooperative relationship is broken.

　Professor Hitoshi Yamamoto of the Faculty of Business Administration of Rissho University, who led this research, showed that if escape behavior is possible, it is possible to maintain a cooperative society without using "repeat" behavior. There is a possibility of pushing it out.

Paper information:[Physical Review E] Effect of voluntary participation on an alternating and a simultaneous prisoner's dilemma