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Delusion proneness and ‘jumping to conclusions’: relative and absolute effects

Published online by Cambridge University Press:  30 September 2014

L. van der Leer ,
B. Hartig ,
M. Goldmanis  and
R. McKay
L. van der Leer
Affiliation:
ARC Centre of Excellence in Cognition and its Disorders, Department of Psychology, Royal Holloway, University of London, Egham, Surrey, UK
B. Hartig
Affiliation:
Department of Economics, Royal Holloway, University of London, Egham, Surrey, UK
M. Goldmanis
Affiliation:
Department of Economics, Royal Holloway, University of London, Egham, Surrey, UK
R. McKay*
Affiliation:
ARC Centre of Excellence in Cognition and its Disorders, Department of Psychology, Royal Holloway, University of London, Egham, Surrey, UK
*
* Address for correspondence: Dr R. McKay, Ph.D., ARC Centre of Excellence in Cognition and its Disorders, Department of Psychology, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK. (Email: [email protected])
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Abstract

Background.

That delusional and delusion-prone individuals ‘jump to conclusions’ is one of the most robust and important findings in the literature on delusions. However, although the notion of ‘jumping to conclusions’ (JTC) implies gathering insufficient evidence and reaching premature decisions, previous studies have not investigated whether the evidence gathering of delusion-prone individuals is, in fact, suboptimal. The standard JTC effect is a relative effect but using relative comparisons to substantiate absolute claims is problematic. In this study we investigated whether delusion-prone participants jump to conclusions in both a relative and an absolute sense.

Method.

Healthy participants (n = 112) completed an incentivized probabilistic reasoning task in which correct decisions were rewarded and additional information could be requested for a small price. This combination of rewards and costs generated optimal decision points. Participants also completed measures of delusion proneness, intelligence and risk aversion.

Results.

Replicating the standard relative finding, we found that delusion proneness significantly predicted task decisions, such that the more delusion prone the participants were, the earlier they decided. This finding was robust when accounting for the effects of risk aversion and intelligence. Importantly, high-delusion-prone participants also decided in advance of an objective rational optimum, gathering fewer data than would have maximized their expected payoff. Surprisingly, we found that even low-delusion-prone participants jumped to conclusions in this absolute sense.

Conclusions.

Our findings support and clarify the claim that delusion formation is associated with a tendency to ‘jump to conclusions’. In short, most people jump to conclusions, but more delusion-prone individuals ‘jump further’.

Keywords

Decision makingdelusion pronenessdelusionsexperimental economicsjumping to conclusions
Type
Original Articles
Information
Psychological Medicine , Volume 45 , Issue 6 , April 2015 , pp. 1253 - 1262
Copyright
Copyright © Cambridge University Press 2014 

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