High Prevalence Information From Different Sources Affects the Development of False Beliefs CELINE VAN GOLDE 1 , STEFANIE J. SHARMAN 2 * and INGRID CANDEL 1 1 Maastricht University, The Netherlands 2 University of New South Wales, Australia SUMMARY To examine the effects of high and low false prevalence information from different sources on false beliefs, subjects took part in two sessions. In the first session, subjects rated the plausibility of different childhood events, how confident they were that they had experienced those events and their memories of those events. In the second session, 2weeks later, subjects received high prevalence information about one target event and low prevalence information about another. Subjects received the information in a third-person description, a newspaper article, or cohort data about previous students’ experiences, or they received no information. High prevalence newspaper and cohort information increased subjects’ plausibility ratings compared to no information and third-person descriptions. High prevalence newspaper information also increased subjects’ belief ratings. Our findings contribute to the growing literature demonstrating the role of false high prevalence information in the development of false beliefs. Copyright # 2009 John Wiley & Sons, Ltd. People can come to believe that they experienced very implausible events—such as witnessing demonic possessions and being abducted by UFOs—if those events are made more plausible (Mazzoni, Loftus, & Kirsch, 2001; Otgaar, Candel, Merckelbach, & Wade, 2009; Pezdek, Blandon-Gitlin, & Gabbay, 2006; Scoboria, Lynn, Hessen, & Fisico, 2007). For example, Mazzoni et al.’s (2001) subjects rated the plausibility of having witnessed a demonic possession as children and their confidence that they had experienced such an event. In a second phase, subjects received mini-articles describing how commonly children witness demonic possessions, the steps that typically occur during demonic possessions and interviews with adults who had witnessed possessions. After reading the mini-articles, subjects not only rated the demonic possession event as more plausible, they also became more confident that they had actually experienced this event in childhood. Recent research has examined the separate effects of the types of information Mazzoni et al. (2001) included in their mini-articles. For example, Hart and Schooler (2006) investigated whether giving subjects prevalence and procedural information affected the development of their false beliefs. First, subjects received fictitious prevalence information describing the commonness of the target event, experiencing a rectal enema in childhood. Second, subjects received procedural information, given in a third-person account, about APPLIED COGNITIVE PSYCHOLOGY Appl. Cognit. Psychol. 24: 152–163 (2010) Published online 16 February 2009 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/acp.1558 *Correspondence to: Stefanie J. Sharman,School of Psychology, University of New South Wales, Sydney, NSW 2052, Australia. E-mail: s.sharman@unsw.edu.au Copyright # 2009 John Wiley & Sons, Ltd.