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

Leslie Van Der Leer, Bjoern Hartig, Maris Goldmanis, Ryan McKay

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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 deci- sions, 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 de- cided in advance of an objective rational optimum, gathering fewer data than would have maximized their expected pay- off. 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’.
Original languageEnglish
Pages (from-to)1253-1262
Number of pages10
JournalPsychological Medicine
Issue number6
Early online date30 Sept 2014
Publication statusPublished - Apr 2015


  • decision-making
  • delusions
  • delusion-proneness
  • jumping to conclusions
  • experimental economics

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