Abstract
The COVID-19 pandemic has been accompanied by an infodemic of misinformation and increasing polarization around public health measures, such as social distancing and national lockdowns. In this study, I examined metacognitive efficiency-the extent to which the subjective feeling of knowing predicts the objective accuracy of knowledge-as a tool to understand and measure the assimilation of misleading misinformation in a balanced sample of Great Britain's population (N = 1689), surveyed at the end of the third national lockdown. Using a signal-detection theory approach to quantify metacognitive efficiency, I found that at the population level, metacognitive efficiency for COVID-19 knowledge was impaired compared with general knowledge, indicating a worse alignment between confidence levels and the actual ability to discern true and false statements. Crucially, individual differences in metacognitive efficiency related to COVID-19 knowledge predicted health-protective behaviours, vaccination intentions and attitudes towards public health measures, even after accounting for the level of knowledge itself and demographic covariates, such as education, income and political alignment. These results reveal the significant impact of misinformation on public beliefs and suggest that fostering confidence in accurate knowledge should be a key target for science communication efforts aimed at promoting compliance with public health and social measures.