The jumping to conclusions bias in delusions: specificity and changeability.

There are indications that a jumping to conclusions bias (JTC) plays a role in the formation and maintenance of delusions and should be targeted in therapy. However, it is unclear whether (a) JTC is uniquely associated with delusions or simply an epiphenomenon of schizophrenia or impaired intellectual functioning and (b) it can be changed by varying task demands, motivational factors, or feedback. Seventy-one patients with schizophrenia spectrum disorders and either acute or remitted delusions and 68 healthy controls were included. Patients were assessed with self- and observer-rated symptom measures. All participants were assessed for intellectual ability and performed the classic beads task with a ratio of 80:20. They were then presented with task variations that involved increasing the difficulty of the ratio to 60:40, introducing a rule for which correct decisions were rewarded by monetary gains and false decisions led to financial losses, and providing feedback on the accuracy of the previous decisions. Participants with current delusional symptoms took fewer draws to decision (DTD) than did those in remission and healthy controls. DTD were associated with observer-rated delusions, but controlling for negative symptoms or intelligence rendered this association insignificant. DTD increased after the difficulty of the task increased and after feedback. The study demonstrated that JTC is linked to delusions but that this association is not unique. Patients with delusions are principally able to adapt their decisions to altered conditions but still decide relatively quickly even when decisions have negative consequences. These difficulties might stem in part from impaired intellectual functioning.