Polarize, Catalyze, Stabilize: Conscience and the evolution of cooperation

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Abstract
Much of the literature on the evolution of cooperation focuses on mechanisms such as reciprocity, indirect reciprocity, and altruistic punishment, all of which require group knowledge of individual actions. But what if no one is looking? What keeps people cooperating then? Conscience, an internal enforcer of cooperation, could be the answer. In this paper, we model conscience as the internalization of societal norms: individuals with conscience internalize a tendency to cooperate in a public goods game, as long as the majority of their community does the same (regardless of whether anyone was watching). Using two very different agent-based models, we sought to determine the evolutionary viability of this rudimentary conscience, as well as its impact on the evolution of cooperation. We found that, in both models, conscience was evolutionarily viable under reasonable group-selective forces. Furthermore, conscience affected the dynamics of cooperation in three ways. First, conscience polarized communities: groups with a high prevalence of conscience gravitated either to near-full cooperation or to near-zero cooperation. Second, conscience catalyzed cooperation: its tendency to polarize magnified differences between groups, thereby facilitating the group-level selection in favor of cooperative groups. Third, in one of our models, conscience stabilized cooperation: the prevalence of conscience tended to decrease when cooperation was high and increase when cooperation was low, thereby dampening fluctuations in the level of cooperation.