Belief-bias reasoning in non-clinical delusion-prone individuals

- Individuals with delusions are hypothesized to have difficulty inhibiting beliefs.
- Two non-clinical groups took part: high and low delusion-prone (high-DP and low-DP).
- The high-DP group had greater difficulty on tests of general inhibition.
- The high-DP group also had greater difficulty on a conditional reasoning task.
- But items that required inhibition of real-world beliefs were no more difficult .

Background and ObjectivesIt has been proposed that people with delusions have difficulty inhibiting beliefs (i.e., “doxastic inhibition”) so as to reason about them as if they might not be true. We used a continuity approach to test this proposal in non-clinical adults scoring high and low in psychometrically assessed delusion-proneness. High delusion-prone individuals were expected to show greater difficulty than low delusion-prone individuals on “conflict” items of a “belief-bias” reasoning task (i.e. when required to reason logically about statements that conflicted with reality), but not on “non-conflict” items.MethodsTwenty high delusion-prone and twenty low delusion-prone participants (according to the Peters et al. Delusions Inventory) completed a belief-bias reasoning task and tests of IQ, working memory and general inhibition (Excluded Letter Fluency, Stroop and Hayling Sentence Completion).ResultsHigh delusion-prone individuals showed greater difficulty than low delusion-prone individuals on the Stroop and Excluded Letter Fluency tests of inhibition, but no greater difficulty on the conflict versus non-conflict items of the belief-bias task. They did, however, make significantly more errors overall on the belief-bias task, despite controlling for IQ, working memory and general inhibitory control.LimitationsThe study had a relatively small sample size and used non-clinical participants to test a theory of cognitive processing in individuals with clinically diagnosed delusions.ConclusionsResults failed to support a role for doxastic inhibitory failure in non-clinical delusion-prone individuals. These individuals did, however, show difficulty with conditional reasoning about statements that may or may not conflict with reality, independent of any general cognitive or inhibitory deficits.