When Randomness Beats Redundancy: Insights into the Diffusion of Complex Contagions

Abstract: How does social network structure amplify or stifle behavior diffusion? Existing theory suggests that when social reinforcement makes the adoption of behavior more likely, it should spread more -- both farther and faster -- on clustered networks with redundant ties. Conversely, if adoption does not benefit from social reinforcement, then it should spread more on random networks without such redundancies. We develop a novel model of behavior diffusion with tunable probabilistic adoption and social reinforcement parameters to systematically evaluate the conditions under which clustered networks better spread a behavior compared to random networks. Using both simulations and analytical techniques we find precise boundaries in the parameter space where either network type outperforms the other or performs equally. We find that in most cases, random networks spread a behavior equally as far or farther compared to clustered networks despite strong social reinforcement. While there are regions in which clustered networks better diffuse contagions with social reinforcement, this only holds when the diffusion process approaches that of a deterministic threshold model and does not hold for all socially reinforced behaviors more generally. At best, clustered networks only outperform random networks by at least a five percent margin in 18\% of the parameter space, and when social reinforcement is large relative to the baseline probability of adoption.