Page 334 - Understanding Psychology

Figure 12.3 Some Biological and Social Needs
Food
Water
Oxygen
Sleep
Avoidance of pain
Need to excel
Need for social bonds
Need to nourish and protect others Need to influence or control others Need for orderliness
Need for fun and relaxation
Whereas biological needs are physiological require- ments critical to our survival, we acquire social needs through experience and learning. Which needs do you think we try to satisfy first?
Some behavior is determined by the internal, or physiological, state of the organ- ism. Like other animals, human beings have certain survival needs. Our biological needs are critical to our survival and physical well- being (see Figure 12.3). The nervous system is constructed in such a way that dramatic vari- ations in blood sugar, water, oxygen, salt, or essential vitamins lead to changes in behav- ior designed to return the body to a condi- tion of chemical balance. The first part of this section discusses the role of such physiologi- cal factors in motivating behavior.
All organisms, including humans, have built-in regulating systems that work like ther- mostats to maintain such internal processes as body temperature, the level of sugar in the blood, and the production of hormones. When the level of thyroxine in the blood- stream is low, the pituitary gland secretes a thyroid-stimulating hormone, causing the
Some Biological Needs
Some Social Needs
BIOLOGICAL MOTIVES
Source: Adapted from Introduction to Psychology, Plotnik, 1999.
lateral hypothalamus (LH): the part of the hypothal-
thyroid gland to secrete more thyroxine. When the thyroxine level is high, the pituitary gland stops producing this hormone. Similarly, when your body temperature drops below a certain point, you start to shiver, certain blood vessels constrict, and you put on more clothes. All these activities reduce heat loss and bring body temperature back to the correct level. If your body heat rises above a certain point, you start to sweat, certain blood vessels dilate, and you remove some clothes. These processes cool you.
The tendency of all organisms to correct imbalances and deviations from their normal state is known as homeostasis. Several of the drives that motivate behavior are homeostatic—hunger, for example.
Hunger
What motivates you to seek food? Often you eat because the sight and smell of, say, pizza tempts you into a restaurant. Other times you eat out of habit because you always have lunch at 12:30 or to be sociable because a friend invites you out for a snack. Yet suppose you are working frantically to finish a term paper. You do not have any food, so you ignore the fact that it is dinnertime and you keep working. At some point your body will start to demand food. You may feel an aching sensation in your stomach. What produces this sensation? What makes you feel hungry?
Your body requires food to grow, to repair itself, and to store reserves. To what is it responding? If the portion of the hypothalamus called the lateral hypothalamus (LH) is stimulated with electrodes, a laboratory animal will begin eating, even if it has just finished a large meal.
amus that produces hunger
signals Conversely, if the LH is removed surgically, an animal will stop eating
320 Chapter 12 / Motivation and Emotion