Human Drives
Let us take a quick look at our phYSiological drives, which we relate to daily, to give us a start toward understanding S0me of the complexities of motivation. In hunger we eat both out of need, out of habit, and for some people because of the cues from the external environment mentioned in the opening paragraph of this chapter. In one experiment clocks were changed to present false time cues. It was found that normal weight subjects based their eating only on how they felt internally, but fat subjects ate almost twice as much when they thought it was 6:05 P.M. as they did when they thought it was 5:20 P.M. Other studies show that when the food is uninspiring and the eating situation is uninteresting, the fat subject eats little, but the normal subject seems less affected by such external circumstances that surround the eating routine. There may be some basis for the old adage, "The thin man eats to live, but the fat man lives to eat." Stanley Schachter, who has studied many aspects of eating behavior, believes that fat people are relatively insensitive to internal cues but highly sensitive to environmental food-related cues. This makes it difficult in the long run for people to stay on diets.
The act of drinking in response to thirst illustrates how the "osmoreceptors" in the hypothalamus of the brain functions to turn the water need on and off. These cells regulate thirst in a manner where dehydration produces changes in the tension of the walls of the osmoreceptors. These cells are sensitive to changes in the osmotic pressure of the blood plasma, changes that initiate excitatory nerve activity that results in the thirst drive. Thirst persists until the water level is restored. But as we all experience, drinking water does not reduce the felt need immediately. It takes from five to fifteen minutes for water to be made available to deh} drated Lody tissue.
Sexual excitement is a drive state in the human that shows a "systems arousal." Sex hormones in both male and female help sexual behavior as part of a system; for example, when the appropriate stimuli are not present, sex hormones alone are not likely to stir up the organism. During the early part of intercourse, breathing becomes faster and deeper. As orgasm approaches, muscles become tense, salivation is exaggerated, and the mouth opens. Inhibitions are relieved as the orgasm nears, and there is a tendency to become aware of one's surroundings as the sexual experience reaches climax. Clinical studies show that under some circumstances subjects report a feeling of well-being after coital orgasm; in some others rhere may be feelings of remorse. For some there is a difference in sexual behavior between those in love versus those for whom the act is only biological or professional. This emphasizes the point that sexual satisfaction relates not only to the "physiological" but also to the "psychological." Learning is an aspect of the "systems arousal" and relates to physiological conditions, stimulating opportunities, cultural conditioning, and even the availability of erotic literature. The touch, pressure, and temperature mechanisms serve to reinforce visual
5tirnulation. as they relate to patterns of behavior learned from experience. Habit often determines the way human beings express their sexual motivation and the kinds of outlet they prefer. The
ypothalamus of the brain contains the "sex center" for both experence and behavior which serves in regulating the systems arousal.
Most drive mechanisms relate to active striving, sleep beinog an exception. Here the drive involves passive resting. Learning sleep abits is important and studies show individual differences in sleep patterns. Laboratory studies confirm our experience that a disturbed frame of mind interferes with good sleep, whether it be worry or some form of cre.ative excitement. Studies also show that we can "catch up" on sleep, but we cannot "store it up" in advance.
