Discontinuous Wealth-Gradient Transition Driving Cooperation

TL;DR

This paper introduces a game-theoretic model where wealth-based payoff scaling on a lattice promotes cooperation through a discontinuous transition, with fluctuations further enhancing cooperative dominance.

Contribution

It reveals a novel wealth-gradient mechanism causing a discontinuous transition that promotes cooperation, influenced by wealth heterogeneity and strategic history.

Findings

Wealth scaling allows cooperators to outperform defectors at high costs.

Discontinuous transition occurs at a critical cost-benefit ratio.

Higher fluctuations strengthen cooperation promotion.

Abstract

The universal prevalence of cooperation is puzzling, as defection typically yields higher payoffs than cooperation, motivating searches for hidden pathways to cooperation. Here we study a game-theoretic model on a lattice structured population in which interaction payoffs are scaled by the minimum of participants' accumulated wealth, reflecting real-world heterogeneity and incorporating the influence of past strategic choices. This wealth scaling allows frequent cooperators to surpass defectors in payoffs through their greater wealth even at high cooperation costs where defection would otherwise dominate. At the elevated critical cost-benefit ratio, the wealth gradient at the cooperator-defector boundary in one dimension exhibits a discontinuous transition. We show that slowing and effective stalling of the boundary trigger an explosive buildup of the wealth gradient, driving the dominance of cooperation below the critical ratio. Remarkably, this promotion of cooperation is stronger at higher temperatures, revealing a constructive role of fluctuations.