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, hut 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 he 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
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 tile 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 eves 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
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 l2th 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 that
prepares the kitten for more serious situations later in life.
7) The passage asserts that animal social hierarchies are
generally stable because:
a) the behavior responses of the group are known by all its
b) the defensive threat posture quickly stops most conflicts.
c) inferior animals usually defer to their physical superior.
d) the need for mutual protection from other species
inhibits conspecific aggression.
8) According to the author, what is the most significant
physiological change undergone by a cat assuming the
defensive threat position?
a) An increase in cardiovascular activity
b) A sudden narrowing of the eyes
c) A contraction of the abdominal muscles
d) The author does not say which change is most significant
9) Based on the information in the passage about agonistic
behavior, it is reasonable to conclude that:
I. the purpose of agonistic behavior is to help ensure the
survival of the species.
II. agonistic behavior is both innate and learned.
III. conspecific aggression is more frequent than i aggression.
a) I only
b) II only
c) I and II only
d) I,II and III only
10) Which of the following would be most in accord with the
information presented in the passage?
a) The aggressive behavior of sharks is closely inked to
their need to remain in constant motion.
b) fine inability of newborn mice to exhibit the attack
response proves that aggressive behavior must be learned.
c) Most animal species that do riot exhibit aggressive
behavior are prevented from doing so by environmental factors.
d) Members of a certain species of hawk use the same method
to prey on both squirrels and gophers.
11) The author suggests that the question of whether
agonistic behavior is genetically programmed or learned:
a) still generates considerable controversy among animal
b) was first investigated through experiments on mice.
c) is outdated since most scientists now believe the genetic
element to be most important.
d) has been the subject of extensive clinical study.
12) Which of the following topics related to agonistic
behavior is NOT explicitly addressed in the passage?
a) The physiological changes that accompany attack behavior
b) The evolutionary purpose of aggression
c) Conspecific aggression that occurs in dominance hierarchies
d) The relationship between play and aggression
13) The author of this passage is primarily concerned with:
a) analyzing the differences between attack behavior and
defensive threat behavior.
b) introducing a subject currently debated among animal
c) providing a general overview of aggressive behavior in
d) illustrating various manifestations of agonistic behavior