title: "Jumping to conclusions" in delusion-prone participants: an experimental economics approach.
abstract: BACKGROUND
  That delusional and delusion-prone individuals "jump to conclusions" on probabilistic reasoning tasks is a key finding in cognitive neuropsychiatry. Here we focused on a less frequently investigated aspect of "jumping to conclusions" (JTC): certainty judgments. We incorporated rigorous procedures from experimental economics to eliminate potential confounds of miscomprehension and motivation and systematically investigated the effect of incentives on task performance.
  
  
  METHODS
  Low- and high-delusion-prone participants (n = 109) completed a series of computerised trials; on each trial, they were shown a black or a white fish, caught from one of the two lakes containing fish of both colours in complementary ratios. In the betting condition, participants were given £4 to distribute over the two lakes as they wished; in the control condition, participants simply provided an estimate of how probable each lake was. Deviations from Bayesian probabilities were investigated.
  
  
  RESULTS
  Whereas high-delusion-prone participants in both the control and betting conditions underestimated the Bayesian probabilities (i.e. were conservative), low-delusion-prone participants in the control condition underestimated but those in the betting condition provided accurate estimates. In the control condition, there was a trend for high-delusion-prone participants to give higher estimates than low-delusion-prone participants, which is consistent with previous reports of "jumping to conclusions" in delusion-prone participants. However, our findings in the betting condition, where high-delusion-prone participants provided lower estimates than low-delusion-prone participants (who were accurate), are inconsistent with the jumping-to-conclusions effect in both a relative and an absolute sense.
  
  
  CONCLUSIONS
  Our findings highlight the key role of task incentives and underscore the importance of comparing the responses of delusion-prone participants to an objective rational standard as well as to the responses of non-delusion-prone participants.
authors: a ARC Centre of Excellence in Cognition and its Disorders, Department of Psychology, Royal Holloway , University of London , Egham , TW20 0EX Surrey , UK.
authors: Leslie
authors: L
authors: van der Leer
authors: Ryan
authors: R
authors: McKay
mesh_terms: D000293:Adolescent; D000328:Adult; D001499:Bayes Theorem; D003657:Decision Making; D003702:Delusions / Q000523:psychology*; D060909:Economics, Behavioral; D005260:Female; D006801:Humans; D007600:Judgment; D008297:Male; D009042:Motivation; D011337:Probability Learning; D012309:Risk-Taking; D013850:Thinking; D055815:Young Adult