Manipulating Consumers with the Truth: Relative-Difference Claims in Advertising and Inferences of Manipulative Intent

Advertisements often feature numeric claims comparing risks associated with one alternative (e.g., control) to another (treatment). Differences may be expressed in either absolute (Modified Rate - Starting Rate) or relative ([Modified Rate - Starting Rate] / Starting Rate) terms. For example, assume a new heart disease treatment reduces the five-year mortality rate from 7.5% (starting risk) to 4% (modified risk). The absolute difference in this case is 3.5%, whereas the relative difference is 46.6%. Because relative differences appear larger, they positively influence evaluations and are therefore more often used in advertising. Unfortunately, baseline information (starting and modified rates) is often omitted or featured inconspicuously in an advertisement. In three experiments, we find that consumers ignore baseline information and instead rely on the magnitude of the difference in forming judgments (Study 1) unless they are motivated to elaborate on the relative-difference claim (Study 2). When motivated, inferences of manipulative intent (IMIs) are activated, which reduce evaluations. In Study 3, when motivated consumers' ability to interpret a relative difference is enhanced, IMIs are affected by the magnitude of the absolute difference. Our findings suggest that motivated consumers or those with the ability to understand relative-difference claims find their use to be manipulative.