Physical Knowledge in Infancy: Reflections on Piaget's Theory
Elizabeth S. Spelke
This chapter focuses on two theses that are central to Piaget's theory of the development of physical knowledge ( Piaget, 1954, 1969, 1974). One thesis concerns developmental changes in conceptions of the world. The other thesis concerns the relation of knowledge to perception.
First, Piaget proposed that conceptions of the physical world undergo revolutionary change in infancy and childhood. The most dramatic changes occur in infancy. In Piaget's view, young infants conceive of physical phenomena as emanating from their own actions. By the close of infancy, in contrast, children conceive the physical world as composed of objects, including themselves, whose behavior is governed by physical laws. For Piaget, this change was as radical as the conceptual changes that occur during scientific revolutions. In particular, Piaget and Inhelder ( 1969) likened the child's construction of a world of physical objects to the construction, in 16th- century astronomy, of the heliocentric universe. The conceptual revolution in infancy may be deeper than the Copernican revolution, however, because astronomers throughout history have shared a view of the self in relation to the external world: a view that is not shared, Piaget believed, by infants.
Second, Piaget proposed that children's conceptions are inextricably tied to their perceptions: Perception and thought are two aspects of a single developing capacity. In particular, the child who cannot conceive the world as composed of law-governed objects also cannot apprehend objects in his or her immediate surroundings: The child perceives a world of ephemeral appearances, not of stable and enduring bodies. Here again, a parallel is