Developmental psychology.pdf

Principles of Motivation 305
Drive-Reduction Theory
Years ago some psychologists described motivation in terms of drive-reduction theory,
meaning that the behavior of organisms is directed primarily toward dispelling bodily
tension. Some pain or discomfort occurs, as in the lack of water or sleep, and the organism
attempts to alleviate this condition. The reward lies in the satisfaction of some
biological or even psychological need.
Concept of Homeostasis One process that clearly supports this view is homeostasis,
which is the automatic tendency of the body to maintain a proper internal environment,
chiefly in its chemical composition. The maintenance of this delicate balance is one of
the most remarkable features of human physiology. Even a few moments without proper
circulatory, respiratory, and other functions can create a disequilibrium endangering
the entire organism. Hence there must be constant restorative reactions.
Body temperature, for example, is influenced by several reactions, one of which
is perspiration. When the body is too hot, perspiration occurs; the body becomes watercooled,
losing heat through the process of evaporation. When the body is too cold, it
begins to shiver, maintaining or generating heat through muscular movement. In both
instances there are also automatic changes in the size of the capillaries. In vasodilation
the capillaries grow wider, sending more blood to the surface of the body, resulting in
heat loss through radiation. When the body is cold, vasoconstriction occurs, which helps
keep the heat by restricting the flow of blood in peripheral areas.
There are countless other homeostatic processes, many of which are automatic.
An adequate oxygen supply is achieved by complex reflexes that increase respiration
when there is an oxygen deficiency in the blood. The removal of damaged body
cells also occurs automatically, as a result of the action of white blood cells. We do not
understand all of these stabilizing factors, but it is clear that this automatic control of
temperature, oxygen, and certain conditions of nutrition gives the organism greater
freedom to engage in higher-level activities. Human beings can write books, maintain
friendships, and travel to distant parts of the world because their vital organs are maintained
in a relatively constant environment.
Other compensatory activities of homeostasis are not automatic. They require
voluntary motivated behavior on the part of the organism. In thirst and hunger the
organism must react to restore its equilibrium. Optimal amounts of fluid, sugar, salt,
fat, and proteins in the blood are achieved by finding and consuming appropriate
amounts of water and food. Similarly, a satisfactory body temperature is sometimes
achieved by engaging in vigorous activity in cold weather and avoiding strenuous activity
in warm weather. The behavior of any organism is periodically concerned with
reestablishing a balanced physiological condition (Figure 11.15).
Figure 11.15
Compensatory Clothing. The Arab
and the Eskimo live in very different
climates. Their similar dress reflects
an effort to deal with a severe climate
and thereby to maintain a normal
body temperature.