UC Berkeley

We propose and test the overconfidence transmission hypothesis, which predicts that individuals calibrate their self-assessments in response to the confidence others display in their social group. Six studies that deploy a mix of correlational and experimental methods support this hypothesis. Evidence indicates that individuals randomly assigned to collaborate in laboratory dyads converged on levels of overconfidence about their own performance rankings. In a controlled experimental context, observing overconfident peers causally increased an individual's degree of bias. The transmission effect persisted over time and across task domains, elevating overconfidence even days after initial exposure. In addition, overconfidence spread across indirect social ties (person to person to person), and transmission operated outside of reported awareness. However, individuals showed a selective in-group bias; overconfidence was acquired only when displayed by a member of one's in-group (and not out-group), consistent with theoretical notions of selective learning bias. Combined, these results advance understanding of the social factors that underlie interindividual differences in overconfidence and suggest that social transmission processes may be in part responsible for why local confidence norms emerge in groups, teams, and organizations. (PsycInfo Database Record (c) 2021 APA, all rights reserved).