Understanding how individuals revise their political beliefs has important implications for society. In a pre-registered study (N=900) we experimentally separated the predictions of two leading theories of human belief revision—desirability bias and confirmation bias—in the context of the 2016 US presidential election. Participants indicated who they desired to win, and who they believed would win, the election. Following confrontation with evidence that was either consistent or inconsistent with their desires or beliefs, they again indicated who they believed would win. We observed a robust desirability bias—individuals updated their beliefs more if the evidence was consistent (versus inconsistent) with their desired outcome. This bias was independent of whether the evidence was consistent or inconsistent with their prior beliefs. In contrast, we find limited evidence of an independent confirmation bias in belief updating. These results have implications for the relevant psychological theories and for political belief revision in practice.In a NYTimes piece pointing to (marketing) their study, the authors note that:
Our study suggests that political belief polarization may emerge because of peoples’ conflicting desires, not their conflicting beliefs per se. This is rather troubling, as it implies that even if we were to escape from our political echo chambers, it wouldn’t help much. Short of changing what people want to believe, we must find other ways to unify our perceptions of reality.