Psychologists have long debated the role of early experience in social and cognitive development. However, traditional approaches to studying this issue are not well positioned to address this debate. The authors present simulations that indicate that the associations between early experiences and later outcomes should approach different asymptotic values across time, given alternative assumptions about the developmental significance of early experience. To test the predictions of alternative developmental models, the authors examine data from the National Institute of Child Health and Human Development (NICHD) Study of Early Child Care and Youth Development (SECCYD) on maternal sensitivity in the first 3 years of life and its association with social competence and academic skills through age 15. Across multimethod, multi-informant outcome data, results suggest that there may be enduring effects of early caregiving experiences in both of these domains. (Contains 8 tables, 5 figures and 3 footnotes.)