Proceedings of the Annual Meeting of the Cognitive Science Society

In prior research, arguments using both anecdotal andstatistical evidence are more persuasive than arguments usingeither alone (Allen, Bruflat, Fucilla, Kramer, McKellips,Ryan, & Spiegelhoff, 2000; Hornikx, 2005). However, it isless clear how people integrate information when the statisticsand the anecdotes present conflicting information. In threepreregistered experiments, we tested how people integrateconflicting information to judge the efficacy of a medicine ina clinical trial. Participants read either an anecdote fromsomeone in the trial, summary statistics about the trial, orboth types of information. We found that reading an anecdotefrom a member of the trial for whom treatment wasineffective reduced people’s beliefs in a medical treatmenteven when participants received strong evidence that thetreatment was effective. In Experiment 3, we found thatintroducing icon arrays increased the perceived efficacy of thetreatment but did not eliminate the effect of the anecdote.