Sanctions triggered by jealousy help promote the cooperation in spatial prisoner's dilemma games

Human beings have a natural tendency to feel jealous of those who have more than themselves. A previous report found that harmful behavior stemming from jealousy can actually encourage cooperation. The present study considers the efficiency of jealousy-motivated sanctions and the appropriate balance of sanctions and enforcement costs to best encourage cooperation. Through a series of numerical simulations of a spatial prisoner's dilemma game, we find that in the case of a lattice population structure, stronger sanctions and higher sanction efficiency ultimately result in more robust cooperation. In contrast, in the case of a scale-free population structure, higher sanction costs cause the cooperation level to rise.