# Imitating the winner leads to discrimination in spatial prisoner's dilemma model

## TL;DR

This paper presents an agent-based model demonstrating that hierarchical discrimination can emerge from social imitation dynamics, especially under high competition, explaining persistent social inequalities.

## Contribution

It introduces a novel evolutionary model showing how imitation of successful peers leads to hierarchical discrimination based on arbitrary group labels.

## Key findings

- Discriminating strategies dominate under high selection pressure.
- Hierarchical discrimination persists due to social imitation dynamics.
- Discrimination is more prevalent in highly competitive societies.

## Abstract

The occurrence of discrimination is an important problem in the social and economical sciences. Much of the discrimination observed in empirical studies can be explained by the theory of in-group favoritism, which states that people tend to act more positively towards peers whose appearances are more similar to their own. Some studies, however, find hierarchical structures in inter-group relations, where members of low-status groups also favor the high-status group members. These observations cannot be understood in the light of in-group favoritism. Here we present an agent based model in which evolutionary dynamics can result in a hierarchical discrimination between two groups characterized by a meaningless, but observable binary label. We find that discriminating strategies end up dominating the system when the selection pressure is high, i.e. when agents have a much higher probability of imitating their neighbor with the highest payoff. These findings suggest that the puzzling persistence of hierarchical discrimination may result from the evolutionary dynamics of the social system itself, namely the social imitation dynamics. It also predicts that discrimination will occur more often in highly competitive societies.