||IV. Male Animals Are Not Consistently More Aggressive Than Females||Page 5|
The fact that men are not more aggressive than women when individual behavior is carefully analyzed, as cited above, should stimulate a fresh look at the sex differences in animals. Indeed there are indications in the literature that females may be as aggressive as males even in those animal species whose behaviors are usually cited as proving the opposite. For example, a recent paper by two top experimenters in the field (DeBold & Miczek, 1984) begins the discussion as follows:
The present experiments illustrate the complexity of the sexual dimorphism in the aggressive behavior of rats. Females are not, as is commonly stated much less aggressive than males. In fact, they are more aggressive than males toward unfamiliar females. More correctly, male and female rats are sexually dimorphic in terms of the stimuli which elicit aggression and not in terms of males being aggressive and females nonaggressive.
In order to analyze the question in detail, it is necessary to consider the various types of aggressive behavior in animals. Five types will be distinguished here: offense against strange conspecifics; competitive fighting; maternal aggression; defense; and predation. Offense against strange conspecifics and competitive fighting are both under the control of an offense-motivational system, and maternal behavior may well be under its control as well. Defense is controlled by another system, a distinction which is agreed upon by a wide range of investigators (Adams, 1979). Predation is not a social behavior at all, but a behavioral system used to obtain food.
Since we know the brain mechanisms of aggression best from research on the rat, I will begin this discussion with a review of the hormonal factors in the control of rat aggressive behavior (Adams, 1983b).
In the rat there is a special androgen effect which enhances male aggression (offense) against other unfamiliar male rats. I have proposed that the effect is due to a sensory analyzer which is tuned to androgen-dependent pheromones and which facilitates an offense-motivational mechanism. This is responsible for the tendency of certain dominant males to establish and defend territories.
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