||Evolution of Fairness and Group Formation in Multi-Player Ultimatum Games
NISHIMURA, Takeshi ,
OKADA, AkiraSHIRATA, Yasuhiro
2015-08 , Graduate School of Economics, Hitotsubashi University
Group formation is a fundamental activity in human society. Humans often exclude others from a group and divide the group benefit in a fair way only among group members. Such an allocation is called in-group fair. Does natural selection favor an in-group fair allocation? We investigate the evolution of fairness and group formation in a three-person Ultimatum Game (UG) in which the group value depends on its size. In a stochastic model of the frequency-dependent Moran process, natural selection favors the formation of a two-person subgroup in the low mutation limit if its group value exceeds a high proportion (0.7) of that of the largest group. Stochastic evolutionary game theory provides theoretical support to explain the behavior of human subjects in economic experiments of a three-person UG.