Emerging Themes in Cognitive Development presents two volumes of the newest research and theory in cognitive development available at the outset of the 1990s. These ideas are firmly rooted in research from the 1980s and, in some sense, these volumes represent a culmination of that research and of even earlier work. Nevertheless, these volumes are offered as catalysts more than summaries, because each presents the freshest and most recently gathered data of many scientists whose insights have had an important impact on the field. The latest ideas of these researchers will, in some cases, immediately prove to be dominant themes of research and theory. In other cases, of course, it will take longer for the concepts presented to capture the imagination of students and colleagues who are still invested in meritori­ ous research on other themes. In either case, the syntheses and innova­ tions proposed are not likely to escape the careful study of the serious scholar, and it is to such scholars that these volumes are dedicated.