This work consists of two studies, originally published in the American Journal of Orthopsychiatry. They are presented primarily as an experiment in methodology in which the play activities of children, under controlled conditions, are used to study "principles of motivation in social relationships." The first paper, on the use of play technic as experimental procedure, presents statistical summaries of studies in sibling rivalry. A standardized play situation is used. The child is exposed to a play with dolls in which a brother or sister doll observes a new baby nursing at the mother's breast. The author summarizes the activities observed in response to this hostility-provoking situation and presents the details of the dynamic patterns noted. More particularly he notes distinctive primitive patterns of hostility and definite modifications of these of the nature of atoning for, undoing or denying the effects of the hostile acts.
The second paper is a more