Evolution of emotions on networks leads to the evolution of cooperation in social dilemmas

TL;DR

This paper demonstrates that emotions like sympathy and envy, when used as strategies in social dilemmas on different networks, influence the evolution of cooperation, with network structure affecting emotional fixation.

Contribution

It introduces a novel emotional model for strategy imitation in social dilemmas and shows how network heterogeneity influences emotional profiles and cooperation.

Findings

Homogeneous networks lead to high sympathy and envy fixation.

Heterogeneous networks result in low sympathy and envy.

Emotional profiles depend on network structure and payoffs.

Abstract

We show that the resolution of social dilemmas on random graphs and scale-free networks is facilitated by imitating not the strategy of better performing players but rather their emotions. We assume sympathy and envy as the two emotions that determine the strategy of each player by any given interaction, and we define them as probabilities to cooperate with players having a lower and higher payoff, respectively. Starting with a population where all possible combinations of the two emotions are available, the evolutionary process leads to a spontaneous fixation to a single emotional profile that is eventually adopted by all players. However, this emotional profile depends not only on the payoffs but also on the heterogeneity of the interaction network. Homogeneous networks, such as lattices and regular random graphs, lead to fixations that are characterized by high sympathy and high envy, while heterogeneous networks lead to low or modest sympathy but also low envy. Our results thus suggest that public emotions and the propensity to cooperate at large depend, and are in fact determined by the properties of the interaction network.