Interaction between games give rise to the evolution of moral norms of cooperation
Fig 4
The evolution of cooperation depends only on the cost of cooperation.
The cooperative fixed point of the evolutionary dynamics when the game B is a Snow Drift game is plotted for two different mutation rates and two different benefits of cooperation (as indicated in the legend). The mixed strategy equilibrium (MNE) composed of Cuu, Cdu, Ddu, and Ddd, which coincides with the cooperative fixed point for zero mutation rate, is also plotted (orange circles). A cooperative fixed point exists for small costs and becomes unstable for high costs. The dynamics settle in a fully cooperative fixed point for too small costs where only cooperative strategies survive. Here a helping game version of the Prisoner’s Dilemma with payoff values R = b − c, T = b, P = 0, and S = −c is used. A base payoff of π0 = 5 is added to all the individuals. For the Snow Drift game, the base payoff values, presented in Table 1, is used.