Current Topics in Radiation Research, Vol. 5

varies in a predictable manner in relation to the hormonal status of their female partners. Also correlating with these observations was M. Krsiak's demonstration that administration of various drugs to one aggressive mouse modified the aggressive behavior of its fighting partner. J. M. R. Delgado (New Haven) demonstrates that offensive and defensive behavior in monkeys and chimpanzees can be either triggered or stopped by remote tele-stimulation of the brain. An important point of his study was that the effect of brain stimulation depends upon the animal's position in the social hierarchy. Ecological and environmental factors determining incidence and mode of expression of aggression are also emphasized in the papers by Barnett (Glasgow) and C. H. Southwick (Baltimore). A good example of these factors is shown in the great difference seen in aggressiveness when a rat is in its home territory and when it is not. Drug-induced changes in aggression are covered in some detail. In humans diphenyl-hydantoin turns up as one of the most successful drugs for reducing aggressive behavior without undesirable side effects. L. A. Gottschalk (Irvine) describes a method for objectively scoring hostility in verbal communications. He finds that chlordiazepoxide produces short term reductions in verbal hostility, while imipramine increases it. In summary it is evident from this book that we still lack knowledge into the basic processes that modify aggressive behavior and that we badly need an application of ethological methods in the study of human aggression.