Many recent discussions of categories and concepts contrast the perceptual and conceptual bases for categories. These discussions pick up a persistent theme in developmental theory. This theme posits a trend from perception to conception and it has been played throughout the works of Piaget (1929), Vygotsky (1934/1962) and Werner (1948). It is echoed by Flavell (1970), Wohlwill (1962), and Bruner and Olver (1963) and more recently by Gentner (1989) and Keil (1989). The idea is that children shift from perceptually-bound representations of objects that are global and holistic to ones that are principled and articulated along abstract dimensions. So, for example, Flavell (1970) wrote that conceptual development grows from "equivalences based on the more concrete and immediately given perceptual, situational, and functional attributes of objects to equivalences of a more abstract, verbaI-conceptual sort." Since development is directional, this theme implies that conception is in some way "better than" perception.