The Aggression Systems
Evolution of Aggression - Introduction Page 14

Table of Contents


Preface Pages 1 - 2


Human aggression - introduction Pages 3 - 4 - 5 - 6 - 7 - 8


Evolution of aggression - introduction Pages  9 - 10 - 11 - 12 - 13 - 14


Brain mechanisms of aggression - introduction Pages 15 - 16 - 17 - 18 - 19 - 20


Dynamics of aggression - introduction Pages 21 - 22 - 23


The second stage is based on a process of internalization, so that one can become angry at one's own actions as well as those of another. In humans, this is often called the "superego." Whether this can occur in monkeys is a question that has not received sufficient attention.

The third stage, in humans only, makes it possible for people to get angry not only at individuals, but at institutions as well. It is this stage that makes possible the important human capacity for righteous indignation.

In the last two papers in this section, we return to the detailed analysis of the genetic basis of evolution in rodents. Two questions are addressed: the question of "species-specific behaviors" and the nature genetic variation within one species. As is well known, evolution can only occur on the basis of genetic variation.

Species-specific behaviors, it turns out, are quite limited. This is quite different from the impression usually given in textbooks. Instead, most behaviors are quite similar over many related species, as documented in the paper on muroid rodents. Only four categories of agonistic behavior vary among rodent species, and of these only one (threat behaviors) applies to offense.

There are many subtle differences among species on the degree to which hormonal and learning factors alter the function of motivating stimuli. These factors are described in detail in the last section of this book concerning the dynamics of aggression. The differences among individuals within a species may be greater than those between species.

The great variability in hormonal and learning effects on motivating stimuli is best seen in the differences among highly inbred strains of the same species, as documented in the of paper on genetic analysis. Hormonal effects upon motivating stimuli are the principle source of variation in the offense motivational system according to data from the rat and mouse. On the other hand, learning effects upon motivating stimuli are the principle source of variation in the defense motivational system.

Although we don't have detailed genetic information from primates and humans, it seems likely that they have a pattern of genetic variability similar to that of the rat and mouse. The primate and human transformations of offense also involve learning effects on motivating stimuli in most cases. The changes in other components of the motivational system are minimal by comparison.

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