Ellen Peters & Myron Rothbart
Nisbett, Zukier, and Lemley (1981) presented evidence for a “dilution effect” in which information non-predictive of a stimulus person's behavior “watered down” or diluted the predictive value of categorical information diagnostic of that behavior.
Two experiments suggest, however, that non-diagnostic information influences prediction by altering the perceived goodness of fit between the stimulus person and the diagnostic category. We conclude that (a) Nisbett et al. found evidence for dilution because their non-diagnostic items decreased the goodness of fit between the stimulus person and the diagnostic category, and (b) depending on the typicality of the non-diagnostic items, it is possible to dilute, enhance, or leave unchanged the predictability between category and behavior. The structure of social categories and the importance of typicality in the stereotyping process is discussed.
Peters, E., & Rothbart, M. (2000). Typicality can create, eliminate, and reverse the dilution effect. Personality and Social Psychology Bulletin, 26, 177-187.
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