Neuropsychological and symptom correlates of the jumping to conclusions reasoning bias

Student thesis: Doctoral ThesisDoctor of Philosophy


Background: In cognitive models of psychosis, reasoning and reasoning biases are central to the development and maintenance of delusions. In particular, individuals with psychosis tend to gather less data before making a decision, hence ‘jumping to conclusions’ (JTC), compared to the general population. This data-gathering bias makes individuals more likely to reach an inaccurate decision and may thus act as both a vulnerability factor for the development of delusions, and a maintaining factor. However, while evidence for the presence of the bias is robust, understanding of the associated mechanisms is limited, particularly in the early course of psychosis. Understanding what factors may influence the bias in First Episode Psychosis (FEP) will inform the development of early psychological interventions, which may reduce the distress and disability associated with psychosis.

The thesis: The four studies in this thesis examined the neuropsychological and symptom correlates of the JTC data-gathering bias in FEP employing a case-control design.

Method: 140 clinical participants and 132 non-clinical controls completed two versions of a probabilistic reasoning task, the Beads Task. Clinical participants completed measures of psychotic symptoms, and non-clinical participants completed a measure of subclinical psychotic symptoms. All participants completed a comprehensive neuropsychological assessment. Demographic data were collected for all participants.

Results: The JTC data-gathering bias was significantly more prevalent in the clinical group with FEP than in the non-clinical control group, in both versions of the probabilistic task. A clear, very strong association was found between neuropsychological performances and the presence of the JTC bias across the groups. A weak, but significant association was found between the presence of current delusions and the JTC bias in the clinical group. Contrary to expectations, no associations were found between the JTC bias and subclinical psychotic symptoms in the non-clinical control group.

Conclusions: This study is the first to find a link between neuropsychological functioning and the JTC bias in the largest FEP group and non-clinical control group yet reported. The findings of this study elucidate ambiguities in the literature and help clarify the direction of cognitive intervention in psychosis.

Date of Award2013
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorSuzanne Jolley (Supervisor), Robin Murray (Supervisor) & Daniel Freeman (Supervisor)

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