# The Impact of Coevolution and Abstention on the Emergence of Cooperation

## TL;DR

This paper investigates how coevolutionary dynamics and abstention influence the emergence of cooperation in a population playing the Optional Prisoner's Dilemma, showing that coevolution can promote cooperation under certain conditions.

## Contribution

It introduces a coevolutionary model for the Optional Prisoner's Dilemma that demonstrates how coevolution and abstention support the rise of cooperation.

## Key findings

- Coevolutionary rules enable cooperators to survive and dominate.
- Abstainers play a key role in protecting cooperators.
- Cooperation fails under extreme initial abstainer populations or high temptation to defect.

## Abstract

This paper explores the Coevolutionary Optional Prisoner's Dilemma (COPD) game, which is a simple model to coevolve game strategy and link weights of agents playing the Optional Prisoner's Dilemma game. We consider a population of agents placed in a lattice grid with boundary conditions. A number of Monte Carlo simulations are performed to investigate the impacts of the COPD game on the emergence of cooperation. Results show that the coevolutionary rules enable cooperators to survive and even dominate, with the presence of abstainers in the population playing a key role in the protection of cooperators against exploitation from defectors. We observe that in adverse conditions such as when the initial population of abstainers is too scarce/abundant, or when the temptation to defect is very high, cooperation has no chance of emerging. However, when the simple coevolutionary rules are applied, cooperators flourish.