The unintended effects of health information base rates on health risk estimates and behavioral intentions

Abstract

Social marketers and health advertisers often use statistical health information to craft customized messages for specific consumer segments. However, the composition of these segments can vary greatly, inherently resulting in different base rate percentages about the same health issue (e.g. ‘51.9% of all COVID 19-related deaths in the U.S. occurred among Caucasians’ vs. ‘16.6% of all COVID 19-related deaths in the U.S. occurred among Hispanics’) that can potentially lead to different responses from consumers. Therefore, this research examines how individuals process, and respond to, manipulated base rates. Study 1 demonstrates that higher (vs. lower) base rates increase individuals’ healthy behavioural intentions by elevating their risk perceptions. Study 2 uncovers a more complex serial process underlying the impact of base rates on intentions to follow recommended behaviours in health messages. Importantly, we demonstrate a critical effect reversal such that higher base rates have an unintended negative impact on individuals’ compliance intentions when involvement is lower (vs. higher). Overall, our findings show how the use of base rates in health messages can serve as a ‘double-edged sword’.