Physiological Motives
Hunger
Why do you eat? You eat when you feel hungry because your stomach is contracting or your
blood sugar is low, but you also eat because you love the taste of a particular food, and
because you are with friends or family who are eating. Our eating behavior is influenced by
biological, social, and cultural factors.
Early research indicated that stomach contractions caused hunger. Yet even people and
other animals who have had their stomachs removed still experience hunger. Recent
research has revealed receptor cells in the stomach that detect food in the stomach and send
neural impulses along the vagus nerve to our brain, reducing our level of hunger.Hunger and Hormones
Secretion of the hormone cholecystokinin by the small intestine when food enters seems to
stimulate the hypothalamus to reduce our level of hunger. When the small intestine releases
sugars into the blood, blood sugar concentration increases. When blood sugar levels are
high, the pancreas secretes the hormone insulin. For some people, the sight and smell of
appealing food can stimulate the secretion of insulin. High levels of insulin generally
stimulate hunger. Insulin lowers the blood glucose level by increasing the use of glucose in
the tissues, by promoting storage of glucose as glycogen in the liver and muscles, and by
promoting formation of fat from glucose. When blood sugar levels are low, insulin releaseMotivation and Emotion 149Figure 12.1 Maslow’s hierarchy of needs.Love and belongingness needs
to gain acceptance, affection, and avoid loneliness