The metacognitive paradox of OCD: confidence is globally reduced but shows increased sensitivity to local evidence

Confidence is a critical metacognitive signal that guides performance. Biases in confidence, such as excessive doubt, are hallmark features of mental health disorders, especially obsessive- compulsive disorder (OCD). Yet, the underlying neurocognitive mechanisms and how they link to learning and decision-making remain elusive. We asked patients with OCD and matched healthy controls to perform a novel rule-shifting task incorporating trial-by-trial confidence ratings. Using a Bayes-optimal model, we identified two distinct confidence biases: while patients with OCD indicated lower overall confidence, their trial-by-trial confidence ratings more accurately tracked task-relevant information, rendering their confidence reports more Bayes-optimal than those of controls. These findings challenge the idea of a simple, unified metacognitive impairment in OCD. Instead, they suggest that OCD is linked to an enhanced responsiveness to environmental evidence and feedback during decision-making.