# Interacting contagions are indistinguishable from social reinforcement

## TL;DR

This paper shows that interacting simple contagions can appear indistinguishable from complex contagions, complicating the identification of social reinforcement mechanisms and aiding the understanding of infectious disease interactions.

## Contribution

It demonstrates the equivalence between interacting simple contagions and complex contagions, bridging social and biological contagion models.

## Key findings

- Interacting simple contagions are indistinguishable from complex contagions.
- The results highlight challenges in quantifying social reinforcement mechanisms.
- The approach aids in understanding interactions of infectious diseases.

## Abstract

From fake news to innovative technologies, many contagions spread via a process of social reinforcement, where multiple exposures are distinct from prolonged exposure to a single source. Contrarily, biological agents such as Ebola or measles are typically thought to spread as simple contagions. Here, we demonstrate that interacting simple contagions are indistinguishable from complex contagions. In the social context, our results highlight the challenge of identifying and quantifying mechanisms, such as social reinforcement, in a world where an innumerable amount 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.