Perceptual development and category generalization.

This work is concerned with developmental changes in the structure of classifications. The central claim is that young children's undifferentiated perceptions of complex stimuli are highly structured by wholistic similarity whereas older children's perceptions are structured by component dimensions. It is shown in 2 experiments that young children systematically and spontaneously generalize a category if it is well organized by overall similarity but not if it is organized by a criterial dimension. Older children, on the other hand, spontaneously apprehend and extend a category by its dimensional structure. The third experiment was designed to test the hypothesis that criterial property categories are preferred in classification tasks requiring the explicit discovery of a general rule. It was found that younger children's attention to the dimensional relations within a category increases under rule-discovery instructions, although they still have difficulty ignoring wholistic similarity relations. The trend from similarity to dimensional classification is discussed in the context of Piagetian classification tasks and family-resemblance accounts of natural categories.