Evolution and the Ultimatum Game

Abstract

In this paper we review, upgrade, and synthesize existing models from evolutionary game theory, all of which aim at explaining human behaviour in the ultimatum game. Our new and improved versions of Gale et al. (1995), Nowak et al. (2000), and Rand et al. (2013) avoid shortcomings that the original versions have, one of which is that the results in the first and the last are driven by bias in the mutations. We also compare the predictions of these three models with the existing experimental evidence by looking at properties of the distributions of minimal acceptable offers. We find that the observed distributions do not conform to the predictions from Gale et al. (1995), Rand et al. (2013), or any other model in which there is no fitness benefit to rejecting. This does not rule out commitment-based explanations, such as Nowak et al. (2000).

Keywords: Ultimatum game, Fairness, mutation-selection equilibrium, Quantal Response Equilibrium, commitment, experimental evidence