# Islands of cooperation emerge by stigmergic interactions in iterated spatial games

## TL;DR

This paper shows how cooperation can emerge in groups of self-interested agents through indirect signals, leading to areas where cooperative behavior thrives.

## Contribution

A novel mechanism using stigmergic interactions to promote cooperation in spatial games is introduced.

## Key findings

- Agents emitting pheromones when cooperating attract others to form cooperative regions.
- Cooperative regions lead to higher payoffs for agents that respond to pheromone signals.
- Stigmergy enables sustained cooperation in iterated spatial games.

## Abstract

This article focuses on the emergence of cooperation in societies of self-interested agents. In particular, it introduces a mechanism based on indirect—stigmergic—interactions between agents moving in an environment, to express the likeliness of finding cooperative partners. On the one hand, agents that find themselves cooperating with others emit pheromones in their current location, expressing the presence of agents willing to cooperate. On the other hand, agents that sense pheromones tend to move towards regions with a higher pheromone concentration. Results show that this mechanism leads to the emergence of spatial regions where cooperation can be effectively sustained, and in which agents can overall get better payoffs than those agents not taking into account pheromones in their choices.