ABSTRACT
Aggression in male rats is affected by social or situational factors, and this, also, interacts with sex hormones. A male rat housed with a female shows more aggression when confronted by a strange male rat than does a rat housed alone or with another male. In primates, environmental factors are the main influences on aggressive behavior. Whether monkeys are submissive, or dominant and aggressive, depends more on the level of aggression in the environment in which they are reared than on the individual's level of circulating androgens. The inhibitory effect of the cerebral cortex on aggression in humans is shown by the fact that a number of disorders of the cortex are associated with increased aggressiveness. Some female primates show variations in aggressiveness during the menstrual cycle, but the part of the cycle varies. In some it is greatest at the time of ovulation, at others immediately before menstruation.
