What is memory, and how is it used? How does memory differ from perception? Treisman (1992; Musen & Treisman, 1990) wrote of perceiving and encoding as highly similar processes. She also suggested that perceiving and re-perceiving are essentially the same process. Certainly perception and memory are highly intertwined. Many researchers, however, view memory as something different from perception, which is often viewed as the process that provides the data to be encoded into memory. The relation between these concepts is currently being debated, with new evidence suggesting that Treisman may be correct, in that forming memories and updating memories may require similar physiological processes (Nader, Schafe, & Le Doux, 2000). The intimate relation between perception and memory is the subject of this chapter. We describe a number of studies showing that, despite the similarities between the two, perceptual and memory processes appear to exert distinct influences on memory performance during development. This examination is useful to the study of memory because studies of the functioning of these systems in an immature state can assist in determining the extent to which it is useful to think of perception and encoding as one process. In a more general sense, this approach can shed light on the relation between perception and memory as a whole. First, however, we must discuss the definition of memory, to clarify the issues that we are addressing.