Overconfidence in psychosis: The foundation of delusional conviction?

A number of recent studies have identified an "overconfidence effect" in psychosis, whereby people with schizophrenia are overconfident in errors while simultaneously slightly underconfident when accurate. This effect may have implications for why delusions, which are based on inaccurate inferences, perceptions and judgements, are typically held with high conviction. Given the importance the overconfidence effect may have in accounting for delusional conviction, the current narrative review aims to summarise and critique the recent evidence for the effect within schizophrenia. People with schizophrenia were consistently found to be overconfident in errors and slightly underconfident in correct appraisals, and this effect appears not to be an artefact of poor task performance. While the overconfidence effect has been linked to delusion-proneness in the general population, there was less direct evidence linking overconfidence to delusional symptoms in clinical populations. Future studies need to adopt longitudinal designs and include additional measures of overconfidence to investigate this association more appropriately, and to also investigate possible mediators of this postulated relationship, such as dopaminergic activity.