Two studies explored the hypothesis that young children perceive integrally some stimuli that older children perceive separably. In both experiments, kindergarten, second- and fifth-grade children were required to classify sets of stimuli that varied in size and brightness. (SB)

The hypothesis that overall-similarity relations structure both adults' and children's classifications of heterogeneous objects (objects that differ in a variety of ways) was supported in two experiments. When objects varied simultaneously on many dimensions, adults and children constructed classifications that maximized within-category similarity…

Responds to four commentaries on the article by Jones and Smith in this issue. Suggests that the comments derive from the possibility that stable concepts might not exist and from the difficulty of imagining what cognition could be without represented concepts. Discusses traditional approaches to stability and variability, and considers what…

Reviews current research on children's concepts and categories that reflects a growing consensus that nonperceptual knowledge is central to concepts and determines category membership, whereas perceptual knowledge is peripheral in concepts and only a rough guide to category membership. Argues that there is no compelling basis in theory or in data…

Argues that the operating characteristics of perceiving and remembering provide a foundation for progress on detailing the processes through which knowledge is realized in real-time tasks and in detailing the processes of developmental change. Includes three examples to illustrate how forming developmental hypotheses in terms of perceiving and…