Jumping to the wrong conclusions? An investigation of the mechanisms of reasoning errors in delusions

Suzanne Jolley, Claire Thompson, James Hurley, Evelina Medin, Lucy Butler, Paul Bebbington, Graham Dunn, Daniel Freeman, David Fowler, Elizabeth Kuipers, Philippa Garety

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)


Understanding how people with delusions arrive at false conclusions is central to the refinement of cognitive behavioural interventions. Making hasty decisions based on limited data (‘jumping to conclusions’, JTC) is one potential causal mechanism, but reasoning errors may also result from other processes. In this study, we investigated the correlates of reasoning errors under differing task conditions in 204 participants with schizophrenia spectrum psychosis who completed three probabilistic reasoning tasks. Psychotic symptoms, affect, and IQ were also evaluated. We found that hasty decision makers were more likely to draw false conclusions, but only 37% of their reasoning errors were consistent with the limited data they had gathered. The remainder directly contradicted all the presented evidence. Reasoning errors showed task-dependent associations with IQ, affect, and psychotic symptoms. We conclude that limited data-gathering contributes to false conclusions but is not the only mechanism involved. Delusions may also be maintained by a tendency to disregard evidence. Low IQ and emotional biases may contribute to reasoning errors in more complex situations. Cognitive strategies to reduce reasoning errors should therefore extend beyond encouragement to gather more data, and incorporate interventions focused directly on these difficulties.
Original languageEnglish
Pages (from-to)275-282
Number of pages8
JournalPsychiatry Research
Issue number2
Early online date4 Jun 2014
Publication statusPublished - 30 Oct 2014


  • Schizophrenia
  • Psychosis
  • Reasoning
  • Cognitive therapy
  • IQ

Cite this