The use of categories affects classification

Once an item is classified as a member of a category, knowledge about that category may be used. Most research has focused on classification rather than the use of category knowledge. Seven experiments show that in learning to classify and use categories, the use may affect later classifications. Five of the experiments employed a common classification paradigm in which symptom sets were classified into disease categories. After each classification, subjects used the category to decide what treatment should be given. The symptoms that were important for the treatments were later classified more accurately, generated earlier from the disease, and judged to have occurred more frequently. The last two experiments extended this work to new paradigms in which the category use required simple problem solving. Again, the use affected later classifications. The discussion addresses the implications of these results for classification theories and for the study of categories.