The Effect of the Cross-Classification of Items on Category Knowledge
Most items in the world belong to multiple categories: The same item can be a dog, a carnivore, a pet, and a hunting companion. The studies in this dissertation focus on how learning a later classification affects knowledge related to an earlier classification of an item. Using this framework, five experiments investigate the interaction between prior knowledge, knowledge of the initial classification, and subsequent category learning. The first experiment establishes an interaction between experimentally acquired category knowledge and subsequent category learning. When participants learned two sets of categories, classification accuracy of members of the target category set is affected by the items' relationship to the secondary category set. The second and third experiments provide evidence that cross-classifying items can result in the exclusion of some knowledge incorporated into the initial category knowledge. Initially, the participants used information about both diagnostic and non-diagnostic attributes to determine goodness of exemplar ratings for members of the categories. However, when the later cross-classification showed the non-diagnostic attributes were important for the secondary classification, those attributes were given significantly less weight in subsequent goodness of exemplar ratings. The fourth experiment finds further evidence of the exclusion effect, and also suggests that the cross-classification of items can result in an intrusion effect, information about the items that is important during the later learning becomes more available in the prior knowledge. The fifth experiment illustrates that the effect of the cross-classification of items is mediated by the way in which prior knowledge is activated during the secondary learning. The General Discussion addresses the implications for the results of these experiments in terms of real-world category learning, the organization of category knowledge, and the specific mechanisms involved in the modification of prior knowledge. The major findings are important because much research has shown how prior knowledge is able to affect category learning, but this study shows how category learning can result in the modification of prior knowledge.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign