Boundedly Rational Searchers Interacting with Medical Misinformation: Characterizing Context-Dependent Decoy Effects on Credibility and Usefulness Evaluation in Sessions

Characterizing users' judgments and interactions with search engine result pages (SERPs) has been a central theme in Interactive Information Retrieval (IIR) evaluation.In contrast to the perfect rationality assumptions underpinning most existing formal models, people are boundedly rational and are subject to the influence of systematic cognitive biases.To enhance the psychological foundation of user models and better understand the in-situ decisions of boundedly rational users, our between-subject crowdsourcing experiment explored Decoy Effect on users' vulnerability to COVID treatment misinformation, which causes enduring impacts on people's personal health management and wellbeing, and examined the extent to which this effect is moderated by contextual factors and user characteristics.Our results, derived from 540 participants and 2,160 valid SERP evaluation records, indicate that: 1) users' interactions with decoy results may increase their vulnerability to medical misinformation in usefulness and credibility judgments; 2) the size of decoy effect is conditioned by users' prior knowledge and the rank position of decoy results.This research empirically reveals the impact of decoy results on users' context-dependent preferences on ranked search results under varying topics and conditions of medical information evaluation.More broadly, it demonstrates the value of representing and modeling users interacting with information as boundedly rational agents and serves as a step forward towards achieving the goal of truly human-centered IIR.