Social conformity fractures the evolutionary dynamics of cooperation

Cooperation underlies many living and social systems, yet it is often threatened by individuals who gain by exploiting others. Social conformity can help groups coordinate, but it can also lock people into unhelpful norms. Here we show, with a mathematical model of a mixed population, how payoff-seeking learners and conformity-driven learners jointly shape cooperation. Payoff-seeking learners choose the behavior with the higher return, whereas conformity-driven learners follow the behavior that is already common. This coupling creates feedback between material incentives and social norms. We find that conformity can speed convergence toward mutually beneficial behavior when incentives favor coordination, but it can also destroy stable diversity when different behaviors need to coexist. Strong conformity splits the population into long-lived asymmetric states in which cooperation is either maintained despite incentives to exploit it, or suppressed despite incentives to adopt it. These results clarify why cooperation can be both resilient and fragile in norm-guided populations: strong conformity can protect cooperation from being undermined by economic incentives, yet it can also suppress cooperation when payoff-driven forces favor it. Cooperation in social and biological systems is often shaped by the tension between individual incentives and social conformity. Here, the authors use a mathematical model to show that conformity can either stabilize cooperation or suppress it, depending on whether social norms and payoff incentives reinforce or oppose one another.