How Does Network Structure Impact the Speed of Socially Reinforced Diffusion?



How does network structure impact the speed and reach of social contagions? The current view holds that random links facilitate “simple” contagion, but when agents require multiple reinforcements for “complex” adoption, clustered networks are better conduits of social influence. We show that in complex contagion, even low probabilities of adoption upon a single contact would activate an exponential contagion process that tilts the balance in favor of random networks. On the other hand, underappreciated but critical to the race between random and clustered networks is how long agents engage with contagion. Switching back to prior practice and the inactivation of senders and especially receivers shorten the window of engagement for convincing distant contacts and weaken the reach of diffusion on random networks. We propose a simplified framework where clustering primarily enables contagion when repetition matters and receivers lose interest quickly; other- wise, diffusion, simple or complex, is faster on random networks than clustered ones. These mechanisms can inform designing social networks, structuring groups, and seeding of ideas and innovations at a time when the increasing inflow of content from various media limits actors’ engagement with each item, whereas expanding network size and connections speeds up diffusion through distant contacts.


Hazhir Rahmandad is an Associate Professor of System Dynamics at the MIT Sloan School of Management. Hazhir's research applies dynamic modeling to problems spanning strategy and healthcare. His organizational work focuses on understanding challenges to learning in dynamic tasks and their implications for strategies adopted by firms. His health research uses modeling to understand various systemic problems from obesity to depression and COVID-19 pandemic. His methodological work contributes to parameter estimation methods for dynamic models and aggregation of prior statistical findings. Hazhir has published in diverse journals including Management ScienceOrganization ScienceStrategic Management JournalAmerican Journal of Public HealthInternational Journal of Obesity, and System Dynamics Review, among others.

This seminar will take place in T09-67. To join online, find the details below: