Reward and cooperation in the spatial public goods game

TL;DR

This paper investigates how reward strategies influence cooperation in the spatial public goods game, revealing that moderate rewards can effectively promote cooperation through cyclic dominance, despite the costs involved.

Contribution

It introduces rewarding cooperators into the spatial public goods game and analyzes their impact on cooperation dynamics, highlighting the conditions under which rewards outperform punishment.

Findings

Rewards can promote cooperation, especially with low synergy effects.

Moderate rewards may be more effective than high rewards due to cyclic dominance.

Defection remains viable if rewarding is costly.

Abstract

The promise of punishment and reward in promoting public cooperation is debatable. While punishment is traditionally considered more successful than reward, the fact that the cost of punishment frequently fails to offset gains from enhanced cooperation has lead some to reconsider reward as the main catalyst behind collaborative efforts. Here we elaborate on the "stick versus carrot" dilemma by studying the evolution of cooperation in the spatial public goods game, where besides the traditional cooperators and defectors, rewarding cooperators supplement the array of possible strategies. The latter are willing to reward cooperative actions at a personal cost, thus effectively downgrading pure cooperators to second-order free-riders due to their unwillingness to bear these additional costs. Consequently, we find that defection remains viable, especially if the rewarding is costly. Rewards, however, can promote cooperation, especially if the synergetic effects of cooperation are low. Surprisingly, moderate rewards may promote cooperation better than high rewards, which is due to the spontaneous emergence of cyclic dominance between the three strategies.