How Political Overconfidence Fuels Affective Polarization in Cross-cutting Discussions

The Dunning-Kruger effect describes how poor performers overestimate their abilities while top performers underestimate their abilities. This study explores whether this effect explains the ineffectiveness of cross-cutting discussions in reducing affective polarization. We propose a moderated mediation model in which the relationship between cross-cutting discussion (wave 1) and affective polarization (wave 2) is mediated by oppositional responses to disagreements, and this indirect relationship, specifically between cross-cutting discussion and opposition responses, is moderated by political overconfidence. Analyzing panel data from a two-wave online survey, the results suggest that the Dunning-Kruger effect is widespread in political knowledge and influences social media users’ behaviors and attitudes. Specifically, for example, those who are more overconfident engage in cross-cutting discussions, have more oppositional responses (e.g., posting criticisms or clicking “dislike”), and thus become more affectively polarized. This suggests that correcting the public’s perceived bias about their level of political knowledge may help reduce affective polarization.