For more than two decades graduate students have come to the University of Minnesota to work on an ongoing longitudinal study of 180 children and their families begun in 1974. The children have been followed year by year from birth to early adulthood. Of course, the special knowledge developed by any particular group of students has tended to center around the ages of the child subjects during the time those students worked on the project. Thus, some students became knowledgeable, and in time even leading experts, on infant emotional development, temperament, and attachment relationships. Others became experts on the emotional functioning of the preschool child and/or the structure and functioning of the preschool peer group and/or parent–child relationships during the preschool period. Later students mastered the intricacies of friendships and peer group functioning, school adjustment and school-related problems, or the development of the sense of self in middle childhood. More recent students have probed identity formation, adolescent family relationships, the challenges of intimacy in adolescence, and child and adolescent psychopathology.

I have come to lament this situation. This is not because development is less interesting with age. Each period of development has been fascinating, and I doubt that the students thought wistfully about how much more interesting an earlier period might have been.