The evolution of cooperation by social exclusion

TL;DR

This paper introduces a game-theoretical model demonstrating that social exclusion can effectively promote cooperation by removing freeriders, overcoming limitations of costly punishment without needing complex social mechanisms.

Contribution

It presents a novel model of social exclusion that can sustain cooperation even when exclusion is costly and stochastic, without relying on genetic ties or repeated interactions.

Findings

Social exclusion can promote cooperation despite costs.

Limited freeriders prevent second-order freeriders from undermining cooperation.

Exclusion-based cooperation does not require reputation or group selection.

Abstract

The exclusion of freeriders from common privileges or public acceptance is widely found in the real world. Current models on the evolution of cooperation with incentives mostly assume peer sanctioning, whereby a punisher imposes penalties on freeriders at a cost to itself. It is well known that such costly punishment has two substantial difficulties. First, a rare punishing cooperator barely subverts the asocial society of freeriders, and second, natural selection often eliminates punishing cooperators in the presence of non-punishing cooperators (namely, "second-order" freeriders). We present a game-theoretical model of social exclusion in which a punishing cooperator can exclude freeriders from benefit sharing. We show that such social exclusion can overcome the above-mentioned difficulties even if it is costly and stochastic. The results do not require a genetic relationship, repeated interaction, reputation, or group selection. Instead, only a limited number of freeriders are required to prevent the second-order freeriders from eroding the social immune system.