Neurocognitive capabilities modulate the integration of evidence in schizophrenia.

Previous studies have demonstrated a cognitive bias in the integration of disconfirmatory evidence (BADE) in patients with schizophrenia. This bias has been associated with delusions. So far, it is unclear how the integration of evidence is associated with neurocognitive capabilities. In the current study, 31 patients with schizophrenia and 29 healthy controls, matched on age, gender, education and premorbid verbal intelligence, underwent a BADE task. Written scenarios of three consecutive sentences each were presented, which progressively reduced the ambiguity of situations. Participants were asked to rate the plausibility of four possible interpretations and adjust their ratings in response to the provided sentences. Psychometric rating scales and a neuropsychological test battery were applied. Patients displayed a bias in the integration of confirmatory, but not disconfirmatory evidence and a liberal acceptance of belief formation. Correlation analyses revealed no associations of evidence integration with the severity of positive symptoms, but with neurocognitive domains, especially with processing speed, executive functioning, vigilance and working memory. In conclusion, patients with schizophrenia show a bias in evidence integration. Neurocognitive functioning emerged as a modulatory factor that should be considered in further research. Studies investigating BADE in earlier stages of psychosis will be necessary to reveal causal relationships.