Basic to the drive concept is the principle of homeostasis, which refers to the body’s tendency to maintain a constant internal environment.
The healthy individual for example, maintains body temperature within a few degrees. Slight deviations from normal temperature set into operation mechanism that restore the normal condition.
Exposure to cold constricts blood vessels on the body’s surface in order to retain the warmth of the blood, and we shiver which produces heat.
In warm weather, peripheral blood vessels dilate to permit heat to escape, and perspiration has a cooling effect. These are automatic mechanisms designed to keep body temperature within normal range.
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Numerous physiological states must be maintained within fairly narrow limits: the concentration of blood sugar, the levels of oxygen and carbon dioxide in the blood, water balance in the cells, to mention but a few.
Various mechanism within the body operate to keep these conditions stable. Presumably, sensors in the body detect changes from the optimal level and activate mechanisms designed to correct the imbalance. The principle is the same as a furnace thermostat, which turns the heat on when the temperature falls below a certain level and off when the temperature rises.
Hunger and thirst can be viewed as homeostatic mechanism because they initiate behaviour designed to restore the balance of certain substances in the blood. Within the framework of homeostasis, a need is any physiological imbalance or departure from the optimal state; its psychological counterpart is drive. When the physiological imbalance restored, drive is reduced and motivated activity ceases.
Many physiological imbalances can be corrected automatically. The pancreas releases sugar stored in the liver to maintain the proper balance of sugar in the blood. But when automatic mechanisms can no longer maintain a balanced state, the organism becomes aroused (drive is activated) and is motivated to restore the balance.
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A person goes in search of food on feeling the symptoms of low blood-sugar level. Figure 4.6 represents schematically the kind of control system that a homeostatic mechanism of this nature would require.
Psychologists have extended the principles of homeostasis to cover more than just tissue needs or physiological balances. In this broader sense any physiological or psychological imbalance will motivate behaviour designed to restore equilibrium.
A hungry, anxious, uncomfortable or fearful person will be motivated to do something to reduce the tension. As we shall see later, there has been criticism of this view that motivation is solely tension arousal and ceases with tension reduction.