TY - JOUR T1 - Coupled Dynamics of Behavior and Disease Contagion Among Antagonistic Groups JF - bioRxiv DO - 10.1101/2020.06.17.157511 SP - 2020.06.17.157511 AU - Paul E. Smaldino AU - James Holland Jones Y1 - 2020/01/01 UR - http://biorxiv.org/content/early/2020/06/19/2020.06.17.157511.abstract N2 - Disease transmission and behavior change are both fundamentally social phenomena. Behavior change can have profound consequences for disease transmission, and epidemic conditions can favor the more rapid adoption of behavioral innovations. We analyze a simple model of coupled behavior-change and infection in a structured population characterized by homophily and outgroup aversion. Outgroup aversion slows the rate of adoption and leads to bifurcation when outgroup aversion exceeds positive ingroup influence. When the rates of adoption differ by group, high outgroup aversion causes the later-adopting group to have a lower equilibrium adoption fraction, even when the behavior is highly desirable. When disease dynamics are coupled to the behavior-adoption model, a wide variety of dynamics are possible. Homophily can either increase or decrease the final size of the epidemic depending on its relative strength in the two groups and R0 for the infection. When R0 ≈ 1 and homophily is strong in the second group, it can be protective for this group. However, when R0 ≫ 1, we find that strong homophily in the second group, together with outgroup aversion, can lead to a much larger epidemic in that group. Similarly, if the first group is homophilic and the second is not, the second group will have a larger epidemic. Homophily and outgroup aversion can also produce a “second wave” in the first group that follows the peak of the epidemic in the second group. In general, adding outgroup aversion to a population characterized by homophily can result in paradoxical failure to adopt behavior that is protective from infection. These simple models reveal complex dynamics that are suggestive of the processes currently observed under pandemic conditions in culturally and/or politically polarized populations such as the United States.Competing Interest StatementThe authors have declared no competing interest. ER -