Social Media Expression and User Predispositions: Applying the Differential Susceptibility to Media Effects Model to the Study of Issue Polarization

The ability of social media users to express themselves online should be influential for opinion formation, including potential polarization. Still, little is known about how expression interacts with users’ psychological predispositions, especially for controversial topics. The potential for expression to relate to support for social media-based racial justice movements, which could also be affected by underlying feelings of racial resentment, is particularly interesting. We apply the Differential Susceptibility to Media Effects Model (DSMM) to the study of the relationship between social media expression and issue polarization regarding Black Lives Matter. In a survey of social media users conducted during the 2016 U.S. presidential election, we find that racial resentment moderates the relationship between social media expression and support for racial justice movements. Among low-resentment social media users, more frequent expression was associated with less support for Black Lives Matter. In addition, low- versus high-resentment users who expressed themselves on social media more frequently were more polarized in their support for All Lives Matter but less polarized in their support for Black Lives Matter. In line with the DSMM, our findings highlight that users’ psychological predispositions must be taken into account when determining how social media expression relates to issue polarization.