Evolution of moral and double moral standards in structured populations|
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SUMMARY OF RESULTS
Why do friends spontaneously come up with mutually accepted rules, cooperation, and solidarity, while the creation of shared moral standards often fails in large communities? In a ''global village'', where everybody may interact with anybody else, it is not worthwhile to punish people who cheat. Moralists (cooperative individuals who undertake punishment efforts) disappear because of their disadvantage compared to cooperators who do not punish (so-called ''second-order free-riders''). However, cooperators are exploited by free-riders. This creates a ''tragedy of the commons'', where everybody is uncooperative in the end. Yet, when people interact with friends or local neighbors, as most people do, moralists can escape the direct competition with non-punishing cooperators by separating from them. Moreover, in the competition with free-riders, moralists can defend their interests better than non-punishing cooperators. Therefore, while seriously depleted in the beginning, moralists can finally spread all over the world (''who laughs last laughs best effect''). Strikingly, the presence of a few noncooperative individuals (''deviant behavior'') can accelerate the victory of moralists. In order to spread, moralists may also form an ''unholy cooperation'' with people having double moral standards, i.e., free-riders who punish non-cooperative behavior, while being uncooperative themselves. These observations change under strategy mutations as follows. Expectedly, frequent mutations create well-mixed conditions, which support the spreading of defectors. However, when the mutation rate is small, the final stationary state does not differ significantly from the state of the mutation-free case, independently of the values of the punishment fine and cost. Nevertheless, the mutation rate affects the relaxation dynamics. Rare mutations can largely accelerate the spreading of costly punishment. This is due to the fact that the presence of defectors breaks the balance of power between both cooperative strategies, which leads to a different kind of dynamics.
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