Strategic Influence: The Diffusion of Prosocial and Antisocial Behaviors

A growing body of empirical evidence reveals a fundamental asymmetry in the diffusion of social behaviors: prosocial behaviors often exhibit strategic substitutability ("bystander effects"), while antisocial behaviors exhibit strategic complementarities ("licensing effects"). Moreover, even a single behavior (e.g., protest participation) can be a complement in some settings and a substitute in others. To unify these findings, we develop a model of strategic diffusion on networks with positive (prosocial) or negative (antisocial) spillovers. Our results rely on a novel conception of influence, capturing the causal impact of an individual's adoption on others. Prosocial behaviors are complementary in sparse networks but substitutable in dense ones, while antisocial behaviors exhibit the reverse pattern. Our model predicts that prosocial behaviors emerge continuously, while antisocial behaviors exhibit a discontinuous, sudden emergence. Effective policies can target the network density or perceptions of the extent of spillovers to encourage prosocial behaviors and inhibit antisocial ones.