Partner selection and emergence of the merit-based equity norm.

The merit-based equity norm is a widely observed principle of fairness in resource distribution, in which the resources acquired by each individual are expected to be proportional to the contribution. Despite the empirical significance of this principle, theoretical progress in evolutionary explanations of the fairness norm has been limited to an egalitarian norm. In this study, we examined the effect of partner selection on the evolution of the merit-based equity norm in a simple bargaining game. Our agent-based model demonstrates that the merit-based equity norm emerges when the agent can choose to continue the current partnership based on the bargaining result, whereas the egalitarian norm arises in a random matching situation.