The Aggression Systems
Evolution of Aggression - Introduction Page 10

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


In order to trace the transformation of offense, it is best to start from the relatively simple structure of offense in the rat. The following abbreviated description of the model of offense (see diagram on following page) is taken from a more detailed documentation in the paper on muroid rodents and modified according to findings of the paper on competitive and territorial fighting.

Each component (box) in the figure corresponds to a particular set of brain cells and each line corresponds to a neural pathway that connects them. In a later section of the book on brain mechanisms, the particular anatomical location of these cell sets and pathways will be proposed.

The components shown on the left react to stimuli that determine why and when the animal is motivated to display offense behaviors. In rodents, as shown, the stimuli are mostly olfactory (or vomeronasal which is related to olfactory), and they indicate the familiarity of the opponent and its reproductive status. In general, rodents attack strangers, with males attacking strange males and females attacking strange females.

A separate, complementary mechanism is responsible for the behavior of offense that occurs when hungry animals fight over a small scrap of food (competitive fighting).

The components shown on the right react to stimuli that determine how the animal will respond in offense. The animal has a small repertoire of behavioral acts and postures, controlled by motor patterning mechanisms as shown. These include approach locomotion (or chasing), bite-and-kick attack, piloerection (hair standing on end), and particular threat postures called upright posture or sideways posture. Whether or not a particular motor pattern or combination of them is released depends upon the immediate stimulus situation as analyzed from visual and tactile sensory systems.

The operation of the entire offense motivational system is controlled by a single homogeneous set of brain cells according to the model. This set of cells is called the offense motivational mechanism, as shown in the figure. It receives inputs from the various sensory analyzers of motivating stimuli(via two synthesizers) and sends outputs to the various motor patterning mechanisms.

(Continued on next page)

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