Book excerpt: Originally published in 1966 the author challenges the accepted theories of group conflict of the time, such as frustration and maladjustment. For him conflict and its accompanying aggressiveness are features of interaction between groups and he supports this theory with a detailed experimental study of controlled groups. At the time of publication, Dr Otto Klineberg, Director of the International Centre for Intergroup Relations at the Sorbonne wrote: ‘Social scientists everywhere owe a great debt of gratitude to Professor Sherif. The distinguished series of publications for which he and his co-workers are responsible have an honoured place in our libraries. In particular, his contributions to the field of intergroup relations are outstanding; his concept of "superordinate goals", based on a combination of theoretical insight and brilliant experimentation, has become a household word for those concerned with this significant problem. In his new volume, Group Conflict and Co-operation, he carries his analysis much further, not only describing the results of several original investigations, but also building a theoretical appraisal of an extensive research literature. The author has made still another significant contribution toward a better understanding of one of the most complex and disturbing phenomena of our time.’