When A's and B's are C's and D's: The effect of the cross-classification of items on learned concepts

Category learning plays a crucial role in cognition because the acquired concepts are used later for categorization, explanation, communication, problem solving, and inference. However, there is little information about how category learning can affect previously acquired concepts. This issue is especially interesting when one considers items that belong to multiple categories, items that can be cross-classified. The current study investigates a learning situation where one classification set is learned and the knowledge gained is assessed. Then a second, orthogonal classification set is learned for the same items. The experiments show that there is an effect of the cross-classification on judgements made about items in terms of the initial classification set. There seem to be two possible effects of learning a cross-classification for items. The secondary learning causes either an intrusion of attribute information critical for the second classification set, or a specification as to what attributes are critical for the first classification set.