Agonistic behavior, or aggression, is exhibited by most of the more than three million species of animals on this
planet. Animal behaviorists still disagree on a comprehensive definition of the term, but aggressive behavior
can be loosely described as any action that harms an adversary or compels it to retreat. Aggression may serve
many purposes, such as food gathering, establishing territory, and enforcing social hierarchy. In a general
Darwinian sense, however, the purpose of aggressive behavior is to increase the individual animal’s – and thus,
the species’ – chance of survival.
Aggressive behavior may be directed at animals of other species, or it may be conspecific – that is, directed at
members of an animal’s own species. One of the most common examples of conspecific aggression occurs in
the establishment and maintenance of social hierarchies. In a hierarchy, social dominance is usually
established according to physical superiority; the classic example is that of a pecking order among domestic
fowl. The dominance hierarchy may be viewed as a means of social control that reduces the incidence of attack
within a group. Once established, the hierarchy is rarely threatened by disputes because the inferior animal
immediately submits when confronted by a superior.
Two basic types of aggressive behavior are common to most species: attack and defensive threat. Each type
involves a particular pattern of physiological and behavioral responses, which tends not to vary regardless of
the stimulus that provokes it. For example, the pattern of attack behavior in cats involves a series of
movements, such as stalking, biting, seizing with the forepaws and scratching with the hind legs, that changes
very little regardless of the stimulus – that is, regardless of who or what the cat is attacking.
The cat’s defensive threat response offers another set of closely linked physiological and behavioral patterns.
The cardiovascular system begins to pump blood at a faster rate, in preparation for sudden physical activity.
The eyes narrow and the ears flatten against the side of the cat’s head for protection, and other vulnerable
areas of the body such as the stomach and throat are similarly contracted. Growling or hissing noises and erect
fur also signal defensive threat. As with the attack response, this pattern of responses is generated with little
variation regardless of the nature of the stimulus.
Are these aggressive patterns of attack and defensive threat innate, genetically programmed, or are they
learned? The answer seems to be a combination of both. A mouse is helpless at birth, but by its 12th day of life
can assume a defensive threat position by backing up on its hind legs. By the time it is one month old, the
mouse begins to exhibit the attack response. Nonetheless, copious evidence suggests that animals learn and
practice aggressive behavior; one need look no further than the sight of a kitten playing with a ball of string. All
the elements of attack – stalking, pouncing, biting and shaking – are part of the game which prepares the kitten
for more serious situations later in life.
The author suggests that the question of whether agonistic behavior is genetically programmed or learned:
Section: Verbal Reasoning
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