What do we, in fact, know about social development and the role of peers in socialization? Interaction with age-mates during the preschool years received considerable attention from child de velopment researchers from the late 19205through the 1940s The first "child watchers" were struck by the frustrations children would endure in order to maintain contact with age-mates, suffering fights and indignities that inevitably accompany the social interactions of immature beings. Expressions such as "play is the work of the child" reflected not only the value of play in the child's development, but the effort it involved and the distress it entailed. It was apparent that children found the satisfaction of play with companions worth its cost to their peace of mind and comfort.