Pretac~<br > The study of human development is one of the liveliest， most productive<br > areas of psychology. Human capacities for change--both positive and nega-<br > tive-by turns intrigue， dismay， and inspire both the average person and the<br > earnest student of human behavior， In the past two decades， developmental<br > :psychologists have achieved an understanding of these capacities that was<br > once thought to be impossible to reach.<br > Today the field of developmental psychology is in one of the most extensive<br > periods of growth in its history. Not only are greater numbers of people<br > ，entering the :field than in the previous ten years， but also new professional<br > societies and scholarly journals are springing up to encourage and strengthen<br > efforts ，to lackle a wider range of problems and approaches than in the past.<br > We have written this book to give a picture of developmental psychology as Oricnt~tion<br > it is today: an expanding， multifaceted enterprise devoted to understanding<br > both basic principles of psychological development and the circumstances<br > that create new opportunities and demands for children and adolescents in<br > ~he 1990s. To make this picture as faithful as possible， we have given special<br > attention to five characteristics of developmental psychology as a field of<br > study:<br > ~ Topical and chronological approaches， Time study of development includes<br > both an interest in particular topics or domains of human functioning<br > :(e~g.， perception， cognition， and emotions) and an interest in distinc-<br > live developmental features at different limes in the life cycle. Working，<br > :developmental psychologists typically do not think of the field in ei-<br > ther a .fully topical or a consistently chronological perspective. Cur-<br > vently， for example， topical interests overlap and coexist with cbrono-<br > ，logical interests in two periods especially: infancy and adolescence.<br >