Our goal in writing this book was to fill a perceived gap in the early experi­ ence literature. Most existing volumes on early experience and development can be dichotomized on a basic versus an applied dimension. Volumes falling on the basic side are designed for researchers and theoreticians in the biomed­ ical and behavioral sciences. Most existing basic volumes are either primarily based on infrahuman data or are based on single major human studies. In going over these volumes, we are not convinced of the generality of infrahu­ man data to the human level; in addition, we were concerned about the replicability of findings from single studies, however well designed these studies were. As a result, the relevance of data from these volumes to applied human problems is quite limited. In contrast, volumes falling on the applied side are designed primarily for those involved in intervention work with infants and young children. These applied books generally tend to be vague and nonempirical compilations of the views of experts and the collective "wisdom of the ages. " Rarely in applied volumes do we find conclusions based on solid, consistent, empirical findings.