title: Delusion proneness and 'jumping to conclusions': relative and absolute effects.
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.
  
  
  METHODS
  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'.
authors.affiliation: ARC Centre of Excellence in Cognition and its Disorders,Department of Psychology,Royal Holloway,University of London,Egham,Surrey,UK.
authors.forename: L
authors.initials: L
authors.lastname: van der Leer
authors.affiliation: Department of Economics,Royal Holloway,University of London,Egham,Surrey,UK.
authors.forename: B
authors.initials: B
authors.lastname: Hartig
authors.affiliation: Department of Economics,Royal Holloway,University of London,Egham,Surrey,UK.
authors.forename: M
authors.initials: M
authors.lastname: Goldmanis
authors.affiliation: ARC Centre of Excellence in Cognition and its Disorders,Department of Psychology,Royal Holloway,University of London,Egham,Surrey,UK.
authors.forename: R
authors.initials: R
authors.lastname: McKay
mesh_terms: D000328:Adult; D003657:Decision Making / Q000502:physiology*; D003702:Delusions / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007600:Judgment / Q000502:physiology*; D008297:Male; D012201:Reward; D055815:Young Adult
keywords: jumping to conclusions