Understanding Partisan Bias in Judgments of Misinformation: Identity Protection Versus Differential Knowledge

People overaccept information that supports their identity and underaccept information that opposes their identity-a phenomenon known as partisan bias. Although partisan-bias effects in judgments of misinformation are robust and pervasive, there is ongoing debate about whether partisan-bias effects arise from identity-protective motivated reasoning or differential knowledge of identity-congenial versus identity-uncongenial information. Prior empirical work has been unable to differentiate the two accounts because of a reliance on groups with pre-existing differences in knowledge (e.g., Democrats and Republicans). The current research addresses this issue by using randomly assigned rather than pre-existing identities. Across two experiments (N_total = 1,411), adult U.S. Prolific workers showed lower thresholds for accepting information that is congenial versus uncongenial to a randomly assigned identity, despite having no differences in prior knowledge. These results support theories that emphasize identity protection as a factor underlying partisan bias in the acceptance of misinformation, with important practical implications for misinformation interventions.