Does the Dilution Effect Have a Conversational Basis?

The dilution effect refers to the finding that judgments are often unduly influenced by nondiagnostic information, producing regressive judgment. The hypothesis of a conver-sational basis of the dilution effect, advanced in a recent study by Igou and Bless, holds that the effect reflects the operation of the conversational norm of relevance. A critique and reanalysis of their data yields only weak, if any, support for this conversational expla-nation. Furthermore, an experiment (n = 224) does not yield any supportive evidence, and a meta-analysis of available studies likewise supports the conclusion that the dilution effect occurs independently of the operation of conversational norms. However, consis-tent with a social-perceptual explanation, the experiment shows that the dilution effect occurs only for individuals high in personal need for structure. Although conversational norms do not provide the basis for the dilution effect, how they are involved in eliminat-ing this reasoning error is discussed. The Dilution Effect as a Social-Perceptual Phenomenon ceptual account argue that the dilution effect occurs ilarity-matching heuristic when forming judgments re accessible in SPSS format to th ppreciated. Please direct cor-Author’s Note: The data of the experimental study reported in this research a a