title: A pessimistic view of optimistic belief updating.
abstract: Received academic wisdom holds that human judgment is characterized by unrealistic optimism, the tendency to underestimate the likelihood of negative events and overestimate the likelihood of positive events. With recent questions being raised over the degree to which the majority of this research genuinely demonstrates optimism, attention to possible mechanisms generating such a bias becomes ever more important. New studies have now claimed that unrealistic optimism emerges as a result of biased belief updating with distinctive neural correlates in the brain. On a behavioral level, these studies suggest that, for negative events, desirable information is incorporated into personal risk estimates to a greater degree than undesirable information (resulting in a more optimistic outlook). However, using task analyses, simulations, and experiments we demonstrate that this pattern of results is a statistical artifact. In contrast with previous work, we examined participants' use of new information with reference to the normative, Bayesian standard. Simulations reveal the fundamental difficulties that would need to be overcome by any robust test of optimistic updating. No such test presently exists, so that the best one can presently do is perform analyses with a number of techniques, all of which have important weaknesses. Applying these analyses to five experiments shows no evidence of optimistic updating. These results clarify the difficulties involved in studying human 'bias' and cast additional doubt over the status of optimism as a fundamental characteristic of healthy cognition.
authors.affiliation: Department of Psychological Sciences, Birkbeck College, University of London, Malet Street, London WC1E 7HX, United Kingdom; MRC Social, Genetic, & Developmental Psychiatry Centre, De Crespigny Park, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 8AF, United Kingdom.
authors.forename: Punit
authors.initials: P
authors.lastname: Shah
authors.affiliation: Department of Experimental Psychology, University College London, 26 Bedford Way, London WC1H 0AP, United Kingdom. Electronic address: adam.harris@ucl.ac.uk.
authors.forename: Adam J L
authors.initials: AJ
authors.lastname: Harris
authors.affiliation: MRC Social, Genetic, & Developmental Psychiatry Centre, De Crespigny Park, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 8AF, United Kingdom; Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AR, United Kingdom.
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Bird
authors.affiliation: Department of Psychology, University of Surrey, Guildford GU2 7XH, United Kingdom; Department of Psychology, De Crespigny Park, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 8AF, United Kingdom.
authors.forename: Caroline
authors.initials: C
authors.lastname: Catmur
authors.affiliation: Department of Psychological Sciences, Birkbeck College, University of London, Malet Street, London WC1E 7HX, United Kingdom.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Hahn
mesh_terms: D000328:Adult; D001499:Bayes Theorem; D005260:Female; D006801:Humans; D007600:Judgment; D008297:Male; D008960:Models, Psychological; D000067656:Optimism; D000067657:Pessimism; D012306:Risk; D055815:Young Adult
keywords: Bayesian belief updating; Belief updating; Human rationality; Motivated reasoning; Optimism bias; Unrealistic optimism