Strategy intervention for the evolution of fairness

TL;DR

This paper introduces a new evolutionary model incorporating high offers and non-monotonic rejections to study how spite influences fairness evolution, revealing that spite promotes fairness while altruism inhibits it.

Contribution

It explicitly models high-offer rejections and strategy intervention, providing analytical insights into the effects of population structure, mutation, and migration on fairness evolution.

Findings

Spite promotes fairness in structured populations.

Altruism inhibits fairness and is maximized at intermediate mutation rates.

Migration inhibits selfishness and fairness, but promotes altruism and spite.

Abstract

Masses of experiments have shown individual preference for fairness which seems irrational. The reason behind it remains a focus for research. The effect of spite (individuals are only concerned with their own relative standing) on the evolution of fairness has attracted increasing attention from experiments, but only has been implicitly studied in one evolutionary model. The model did not involve high-offer rejections, which have been found in the form of non-monotonic rejections (rejecting offers that are too high or too low) in experiments. Here, we introduce a high offer and a non-monotonic rejection in structured populations of finite size, and use strategy intervention to explicitly study how spite influences the evolution of fairness: five strategies are in sequence added into the competition of a fair strategy and a selfish strategy. We find that spite promotes fairness, altruism inhibits fairness, and the non-monotonic rejection can cause fairness to overcome selfishness, which cannot happen without high-offer rejections. Particularly for the group-structured population with seven discrete strategies, we analytically study the effect of population size, mutation, and migration on fairness, selfishness, altruism, and spite. A larger population size cannot change the dominance of fairness, but it promotes altruism and inhibits selfishness and spite. Intermediate mutation maximizes selfishness and fairness, and minimizes spite; intermediate mutation maximizes altruism for intermediate migration and minimizes altruism otherwise. The existence of migration inhibits selfishness and fairness, and promotes altruism; sufficient migration promotes spite. Our study may provide important insights into the evolutionary origin of fairness.