Unstable belief formation and slowed decision-making: evidence that the jumping-to-conclusions bias in schizophrenia is not linked to impulsive decision-making

Background Jumping-to-conclusions (JTC) is a prominent reasoning bias in schizophrenia (SCZ). While it has been linked to not only psychopathological abnormalities (delusions and impulsive decision-making) but also unstable belief formation, its origin remains unclear. We here directly test to which extend JTC is associated with delusional ideation, impulsive decision-making, and unstable belief formation. Methods In total, 45 SCZ patients were compared with matched samples of 45 patients with major depressive disorder (MDD) and 45 healthy controls (HC) as delusions and JTC also occur in other mental disorders and the general population. Participants performed a probabilistic beads task. To test the association of JTC with measures of delusions (Positive and Negative Syndrome Scale [PANSS]positive, PANSSpositive-factor, and Peter Delusions Inventory [PDI]), Bayesian linear regressions were computed. For the link between JTC and impulsive decision-making and unstable beliefs, we conducted between-group comparisons of “draws to decision” (DTD), “decision times” (DT), and “disconfirmatory evidence scores” (DES). Results Bayesian regression obtained no robust relationship between PDI and DTD (all |R2adj| ≤ .057, all P ≥ .022, all Bayes Factors [BF01] ≤ 0.046; α adj = .00833). Compared with MDD and HC, patients with SCZ needed more time to decide (significantly higher DT in ambiguous trials: all P ≤ .005, r2 ≥ .216; numerically higher DT in other trials). Further, SCZ had unstable beliefs about the correct source jar whenever unexpected changes in bead sequences (disconfirmatory evidence) occurred (compared with MDD: all P ≤ .004 and all r2 ≥ .232; compared with HC: numerically higher DES). No significant correlation was observed between DT and DTD (all P ≥ .050). Conclusions Our findings point toward a relationship of JTC with unstable belief formation and do not support the assumption that JTC is associated with impulsive decision-making.