Patterns of evidence integration in schizophrenia and delusion

Previous studies documented a bias against disconfirmatory evidence (BADE) in
patients affected by schizophrenia spectrum disorders, with some discrepant
findings on its relationship with delusions. In order to further investigate the
patterns of evidence integration in schizophrenia and delusion, we recruited 40
deluded and non-deluded patients with schizophrenia and 40 healthy control
subjects. Participants were administered the BADE test, which consisted of 30
delusion-neutral scenarios, each one progressively described by three subsequent
disambiguating statements and providing four types of interpretation to rate for
plausibility; at every additional evidence presentation, participants were asked
to adjust their ratings. In contrast to previous works, patients displayed both a
BADE and a bias against confirmatory evidence (BACE) relative to healthy
subjects, as they reduced plausibility ratings on incorrect interpretations and
increased plausibility ratings on correct interpretation significantly less over
trial progress. Moreover, BACE and BADE measures showed to discriminate
differentially control from schizophrenia participants and delusional from
non-delusional patients.