 The major objective of this research is to better understand the functional significance of object categorization in early development. The proposed work is designed to examine the emergence of infants ability to access internal categorical representations in service of planning actions on the external environment. Representation, in this capacity, 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, and can form internal representations of such bounded collections. Much less is known, however, about infants ability to actually utilize such representations in the guidance of goal directed action. The present research is designed to characterize the functional and behavioral significance of object representations in infancy, focusing particularly on categorically organized representations. The primary research strategy to be used consists of analyzing infants examination and manipulation of novel objects that vary both in visual i.e., shape and color as well as nonvisual dimensions i.e., weight. In a laboratory procedure, twelve-month old infants will explore novel objects of different weights, and their subsequent handling of modified test objects will be measured with an electronic motion analysis system. Kinematic analyses of infants actions on the test objects will reveal how these actions were prepared in relation to their previous experience with similar objects. 