This work is largely based on what has been a mammoth-one person called it a "heroic" -research project. Both fieldwork and data analyses were laborious and time-consuming, and the work could not have come to fruition without the cooperation of many people. Above all, I owe a debt of gratitude to the mothers and fathers who recognized the importance of such an investigation in building a secure knowledge base concerning human development and who kindly allowed us to come into their homes. The children, at 2 V2, did not have such an appreciation, but naturally I am very grateful to them for the star roles they played in the work. I have to thank all my collaborators for their help in various aspects of the research: Walter Zwirner was statistical consultant to the project, and Pat Olsen and Arlene Grineau were the chief research assistants-! owe particular thanks to them. Others who helped generously with data collection or data analysis (including program writing) were Pat Bachor, Valerie Becker, Rob Black, Doreen Darby, Judy Eser, Con Ferris, Susan Horsley, "Jagan," Ann Johnson, Wayne Miller, Sambhu Nath, Deanna Piwowar, Bruce Roe, Ken Ryba, Laurel Saville, Cecilia Schnurr, Terry Taerum, Debbie Twaddle, and John Wrenshall. Sherry Pitcher kindly prepared the index. Dorice Conway and Reginald Sauve collaborated in the analysis of identical-fraternal twin differences (Chapter 4); Nicholas Martin and Lindon Eaves were chiefly responsible for the biometric-genetic analysis of the data (Chapter 9).
For many years students who took courses in social development had no text available for their use. Those of us who instructed them had to rely on assigning journal articles to be read and providing an overview and syn thesis of the area in our lectures. In the last few years, the situation has changed markedly. There are now several very good textbooks that fill the void, reflecting an increasing interest in this area of research and theory. Here is one more. There are many ways to tell a story. Our book, we think, tells it dif ferently enough to have made it worth the writing. As we began to talk, some time ago, about undertaking this project, we found we had a mutual interest in trying to present the study of social development from a histori cal point of view. The field has changed dramatically from its inception, and we have both been in it long enough to have witnessed first-hand a number of these changes. Modifications of theoretical orientations and the de velopment of increasingly sophisticated and rigorous methodology have brought with them the stimulation of controversy and growth, as social developmental psychologists argued about the best ways of going about their business. Certainly the same things have happened in other areas of psychology, but the arguments seem to have been particularly vigorous in our own domain.