Although few contemporary experts in child development view the first two years of life as a “critical” period during which the path of future development is determined, this stage of development is still regarded by many as being a “sensitive” period, during which trajectories are first established. Because developmental trajectories can be selfsustaining (if not impossible to alter), experiences that shape early development have important ramifications for both science and social policy. In particular, early rearing experiences are thought by many to play an important role in shaping early developmental trajectories, including non-maternal child-care experiences.