The Influence of Base Rate and Case Information on Health-Risk Perceptions: A Unified Model of Self-Positivity and Self-Negativity

This research examines how consumers use base rate (e.g., disease prevalence in a population) and case information (e.g., an individual's disease symptoms) to estimate health risks. Drawing on construal level theory, we propose that consumers' reliance on base rate (case information) will be enhanced (weakened) by psychological distance. A corollary of this premise is that self-positivity (i.e., underestimating self-risk vs. other-risk) is likely when the disease base rate is high but the case information suggests low risk. In contrast, self-negativity (i.e., overestimating self-risk vs. other-risk) is likely when the disease base rate is low, but case information implies high risk. Six experiments provide convergent support for this thesis, using different operationalizations of construal level, base rate, and case risk across multiple health domains. Our findings inform the extant literature on health-risk perception and also provide theoretical implications for research on social comparisons, as well as that on the use of base rate versus case information.