The conversational basis for the dilution effect

The impact of diagnostic information on judgments and in decision making is often reduced when additional, nondiagnostic information is presented. This article argues that the diluting impact of nondiagnostic information results in part from rules of everyday communication, which usually grant relevance to presented information. In an experimental test, participants were presented with positive or negative information about a product. Positive diagnostic information resulted in more favorable judgments than negative diagnostic information. This impact of diagnostic information was diluted when nondiagnostic information was added. Most important, the dilution effect was not observed when the applicability of the conversation was experimentally called into question.