This research will examine the development of conceptual thought in infants and young children and their ability to recall the past. Until recently, we had little information about the way infants conceptualize the world or how long they can recall events that have happened to them. The phenomenon known as infantile amnesia, in which adults recall little or nothing about their early years, suggests that infants may not be able to remember their past for very long. However, recent work in Mandler's laboratory indicates that two-year-olds can recall events that occurred at age one. This research program will use deferred imitation, in which children are asked to imitate events they observed in the past, to measure recall in children too young to talk. There has also been little experimental work on concept formation in infancy. It has traditionally been thought that infants first form concepts about concrete objects, such as dogs, chairs, and cars, and only later develop broader concepts of animals, furniture, and vehicles. However, research from Mandler's laboratory indicates that the broader concepts precede the more specific ones. This research will use several new techniques, involving the way that infants handle and explore objects, to test this hypothesis. The overall goal of the research is to provide a systematic body of knowledge about the preverbal foundations of thinking and remembering, so that we can better understand what young children need to know in order to learn language.