A Randomized Controlled Field Trial of Social Contagion

Human embeddedness in social networks and social contagion can be used to influence the knowledge and behavior of whole populations. With support from the Bill and Melinda Gates Foundation, the National Institute on Aging, the NOMIS Foundation, and other funders, and in partnership with the Ministry of Health in Honduras and the Inter-American Development Bank, we conducted a large-scale randomized controlled field trial of network targeting (that exploited the “friendship paradox” of human social networks — namely, that a person’s friends have more friends than they do), involving 24,000 people in 176 isolated villages in Copan, Honduras. We evaluated methods that can accelerate the spread of health behaviors across social connections, showing that this was feasible in a landmark RCT published in 2024. In this short documentary, we discuss our driving motivations, our research design, and our findings, at the conclusion of the trial.