A generalized bias against disconfirmatory evidence in schizophrenia.

Fixation onto false/unrealistic beliefs is a core feature of schizophrenic delusions. A recent study conducted by our research group has provided evidence for the presence of a bias against disconfirmatory evidence (BADE) in patients with schizophrenia. Importantly, this bias was found with delusion-neutral material. To further validate a BADE as an underlying component of schizophrenic delusions, we recruited 34 presently deluded and non-deluded patients with schizophrenia, along with 26 healthy and 46 mixed psychiatric control participants. Participants were administered a closure task. On each trial, a common object (e.g., elephant) was increasingly disambiguated (i.e., shown in decreasing degrees of fragmentation). The participants were required to assess the plausibility of different interpretations at each of the up to eight stages in each trial. In line with the main hypothesis, patients with schizophrenia downgraded the ratings for incorrect interpretations significantly less over the course of task completion than did healthy and psychiatric controls. In contrast, the gradual upgrading of correct interpretations was similar across all groups, suggesting that the pattern of results obtained for incorrect interpretations reflects a BADE and not a mere repetition of prior responses or a lack of attention to the task at hand. The present study suggests that a BADE is a core feature of schizophrenia, and that this style of thinking is not confined to delusion-congruent scenarios.