The inclusion effect and category-based induction: Theory and application to brand categories

This article investigates inferences between elements in brand categories using an argument strength research paradigm. In 3 laboratory studies of brand categories, we found that consumers often generalize possession of an attribute from a specific category (e.g., Sony televisions) to a more general category (e.g., all Sony products) more readily than they generalize the attribute from the specific category (e.g., Sony televisions) to another specific category (e.g., Sony bicycles) - a counternorrnative phenomenon called the inclusion effect. Consistent with the category induction model of Osherson, Smith, Wilkie, Lopez, and Shafir (1990), the similarity between the premise and conclusion categories (e.g., televisions and bicycles) was a strong predictor of argument strength judgments. We also found that the inclusion effect was attenuated when the specific conclusion category increased in its typicality to the general category (e.g., Sony cameras vs. Sony bicycles). Presenting the general conclusion argument immediately followed by the specific conclusion argument (as opposed to presenting each argument alone) seemed to accentuate the inclusion effect, despite our expectation that increased salience of the judgmental inconsistencies (that lead to the countemormative reasoning) would reduce the effect. Although several rival explanations of the inclusion effect (including a conversational norms explanation) were ruled out, a conclusion plausibility explanation also appeared to account for some of the results.