Selfishness, fraternity, and other-regarding preference in spatial evolutionary games

TL;DR

This paper investigates how varying degrees of other-regarding preferences, from selfishness to fraternity, influence the evolution of cooperation and defection in spatial games on a lattice, revealing optimal societal payoffs at fraternal levels.

Contribution

It introduces a model where players' utility combines personal and neighbors' income, analyzing the impact of fraternity on cooperation using Monte Carlo simulations and stability analysis.

Findings

Fraternal players lead to ordered cooperative arrangements.

Selfish players tend to dominate defectors in certain games.

Optimal societal payoffs occur at fraternal preference levels.

Abstract

Spatial evolutionary games are studied with myopic players whose payoff interest, as a personal character, is tuned from selfishness to other-regarding preference via fraternity. The players are located on a square lattice and collect income from symmetric two-person two-strategy (called cooperation and defection) games with their nearest neighbors. During the elementary steps of evolution a randomly chosen player modifies her strategy in order to maximize stochastically her utility function composed from her own and the co-players' income with weight factors $1-Q$ and Q. These models are studied within a wide range of payoff parameters using Monte Carlo simulations for noisy strategy updates and by spatial stability analysis in the low noise limit. For fraternal players ($Q=1/2$) the system evolves into ordered arrangements of strategies in the low noise limit in a way providing optimum payoff for the whole society. Dominance of defectors, representing the "tragedy of the commons", is found within the regions of prisoner's dilemma and stag hunt game for selfish players (Q=0). Due to the symmetry in the effective utility function the system exhibits similar behavior even for Q=1 that can be interpreted as the "lovers' dilemma".