Just a Big Misunderstanding? Bias and Affective Polarization

Abstract

Extreme partisan animosity, sometimes called partyism, has been on the rise in the US and is prevalent around the world. Much of the research on partyism posits that it is driven by social group identity and/or motivated reasoning. I propose a novel, behavioral economics-based explanation for partyism: the cognitive bias of overprecision (overconfidence in precision of beliefs). Overprecision could cause partyism indirectly via inflated perceptions of social distance, enhanced political extremism, or strengthened partisanship. These effects could then lead to increased partyism for other reasons such as motivated reasoning. Overprecision could also cause partyism directly via excessively strong negative inferences from observed skewed or misunderstood information. Using a nationally representative sample, I find consistent support for direct effects of overprecision and mixed support for indirect effects. The point estimates imply a one standard increase deviation in a respondent's overprecision predicts as much as a 0.71 standard deviation decline in relative out-party favorability.