title: Jumping to the wrong conclusions? An investigation of the mechanisms of reasoning errors in delusions.
abstract: 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.
authors: King׳s College London, Institute of Psychiatry, Department of Psychology, London, UK. Electronic address: Suzanne.jolley@kcl.ac.uk.
authors: Suzanne
authors: S
authors: Jolley
authors: King׳s College London, Institute of Psychiatry, Department of Psychology, London, UK.
authors: Claire
authors: C
authors: Thompson
authors: School of Medicine, Health Policy and Practice, University of East Anglia, Norwich, UK.
authors: James
authors: J
authors: Hurley
authors: School of Medicine, Health Policy and Practice, University of East Anglia, Norwich, UK.
authors: Evelina
authors: E
authors: Medin
authors: King׳s College London, Institute of Psychiatry, Department of Psychology, London, UK.
authors: Lucy
authors: L
authors: Butler
authors: Division of Psychiatry, UCL, London, UK.
authors: Paul
authors: P
authors: Bebbington
authors: Centre for Biostatistics, Institute of Population Health, The University of Manchester and Manchester Academic Health Science Centre, Manchester, UK.
authors: Graham
authors: G
authors: Dunn
authors: Department of Psychiatry, University of Oxford, Oxford, UK.
authors: Daniel
authors: D
authors: Freeman
authors: School of Psychology, University of Sussex, Sussex, UK.
authors: David
authors: D
authors: Fowler
authors: King׳s College London, Institute of Psychiatry, Department of Psychology, London, UK.
authors: Elizabeth
authors: E
authors: Kuipers
authors: King׳s College London, Institute of Psychiatry, Department of Psychology, London, UK.
authors: Philippa
authors: P
authors: Garety
mesh_terms: D000328:Adult; D003657:Decision Making; D003702:Delusions / Q000523:psychology*; D004644:Emotions; D005260:Female; D006801:Humans; D007600:Judgment; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D011618:Psychotic Disorders / Q000523:psychology*; D013850:Thinking
keywords: Cognitive therapy; IQ; Psychosis; Reasoning; Schizophrenia