Awareness of wealth inequalities breeds animosity

Cooperation is a ubiquitous trait among individuals of a species which interbreeds in nature and forms part of groups [1]. Various theories and models have been developed to explain the origins, maintenance, and continuation of cooperation within a generic population. Among these theories is the prisoner's dilemma (PD), which is a well-known framework for investigations on agents’ behavior and strategies [2]. In a traditional PD game, pairwise players are assigned the same initial endowment, and they have no access to (nor knowledge of) the opponents’ wealth throughout the course of the game. In real life, however, circumstances operate which (in most of the cases) unequally, asymmetrically or hierarchically distribute the income and resources, and the group members may be aware (completely or partially) of their opponents’ power and capacity before making their own decision to cooperate or defect. We experimentally reveal the impact of inequality and visibility by means of comparing the results of four sessions where players (1) may have equal or unequal initial endowments and (2) may be visible or invisible to opponents as far as their wealth information is concerned. Our observations disclose that wealth information makes no significant difference to the promotion of cooperation when the initial wealth distribution is fair. In the case of initially unequal endowments, hiding the payoff information enhances the frequency of cooperation while visibility of the opponent's wealth harms group synergy.