Exploring the Psychological Foundations of Ideological and Social Sorting

Americans are sorting ideologically: Liberals and conservatives are more likely to respectively identify as Democrats and Republicans. They are sorting socially as well: Partisans like and trust copartisans more than opposing partisans. Existing explanations for these phenomena rely on exogenous factors, such as elite polarization. But exogenous explanations cannot fully explain variation in sorting. We argue that psychological characteristics can help explain the tendency to sort ideologically or socially. Specifically, we investigate an individual's responsiveness to internal values versus normative social pressures as a determinant of sorting. We test this theory with several nationally representative surveys, as well as one survey experiment, and find strong support that an individual's own tendency to respond to social cues, as opposed to ideological values, has important consequences for this process. Our work allows for a better understanding of the psychological factors that promote partisan sorting and for interpreting variation in the degree to which citizens sort into partisan groups.