Macroscopic patterns of interacting contagions are indistinguishable from social reinforcement

Laurent Hébert-Dufresne, Samuel V. Scarpino & Jean-Gabriel Young
Nature Physics
February 24, 2020


From ‘fake news’ to innovative technologies, many contagions spread as complex contagions via a process of social reinforcement, where multiple exposures are distinct from prolonged exposure to a single source1. Contrarily, biological agents such as Ebola or measles are typically thought to spread as simple contagions2. Here, we demonstrate that these different spreading mechanisms can have indistinguishable population-level dynamics once multiple contagions interact. In the social context, our results highlight the challenge of identifying and quantifying spreading mechanisms, such as social reinforcement3, in a world where an innumerable number of ideas, memes and behaviors interact. In the biological context, this parallel allows the use of complex contagions to effectively quantify the non-trivial interactions of infectious diseases.

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