The major objective of this research is to better understand the early development of perceptual categorization. The proposed work is designed to examine the emergence of infants' ability to access internal categorical representations. Representation refers simply to stored information that can influence later behavior. Categorization refers to the treatment of discriminable objects as equivalent in some way. Even very young infants appear able to visually categorize diverse sets of discriminable patterns or objects. Much less is known, however, about how infants internally represent and utilize such information. The present set of studies is designed to probe the ontogeny of category of representations in infancy. The methodological strategy to be used in the first study consists of exposing infants to entirely novel configurations of objects for fixed amounts of time and later analyzing infants' examination and manipulation of those objects once they have become familiar. Infants will be exposed to these novel categories of objects at home over a 2-month period. Later, in a laboratory procedure, 5-month-old infants will be tested both with the familiar objects and similar test objects. A second study will utilize eye-tracking technology to examine the nature of infants' eye movements as they visually encode the individual members of complex categories such as animals and vehicles. Finally, a third study is being conducted to examine the relation between individual differences in infants' category learning and subsequent variability in language learning later on in childhood.