4.6 Motivation

Drive-reduction theory says a physical need (like lack of water) creates a drive, an aroused state that pushes you to reduce the need (drinking). The goal is homeostasis, the body's tendency to keep a steady internal state. This explains thirst and hunger well, but not why people do things that raise tension, like riding roller coasters.

Arousal theory fills that gap: people are motivated to keep an optimal level of arousal, not zero arousal. If you're bored, you look for stimulation; if you're overwhelmed, you look for calm. The Yerkes-Dodson law says performance is best at a moderate level of arousal and worse when arousal is very low or very high. The best level depends on the task: easy tasks are done best at somewhat higher arousal, while hard tasks are done best at somewhat lower arousal.

Instincts are inborn, fixed patterns of behavior that a certain stimulus sets off, like a spider spinning a web. They explain a lot of animal behavior, but psychologists don't find them useful for explaining human motivation, because learning and thinking shape so much of what people do.

Self-determination theory says people are motivated by intrinsic motivation, doing something because it's interesting or satisfying in itself, and by extrinsic motivation, doing it for outside rewards or to avoid punishment. The theory also proposes that people need to feel autonomy (choice), competence (skill) and relatedness (connection) to stay intrinsically motivated.

Incentive theory focuses on extrinsic motivation: people are pulled toward rewards and away from punishments in the environment, like working extra shifts for overtime pay. A caution: offering rewards for something people already enjoy can sometimes reduce their intrinsic interest, an effect called the overjustification effect.

Kurt Lewin proposed that motivation often comes from resolving conflicts between choices. There are three kinds.

Sensation-seeking theory says people differ in their need for varied, novel and intense experiences. Its four types are thrill and adventure seeking (risky activities like skydiving), experience seeking (new sensations through travel, music or art), disinhibition (letting loose through parties and other uninhibited social activities) and boredom susceptibility (dislike of routine and repetition). People high in sensation seeking are motivated by novelty itself, which drive-reduction theory can't explain.

Hunger shows how body and mind interact. Ghrelin is a hormone released mainly by an empty stomach that signals hunger; levels rise before meals. Leptin is a hormone released by fat cells that signals fullness (satiety) and helps regulate body weight over the long run. The hypothalamus reads these hormone signals and adjusts how hungry you feel. It also controls the pituitary gland, the 'master gland' (1.4), so expect ghrelin, leptin, the hypothalamus and the pituitary to show up together in hunger questions.

External cues matter too. You may get hungry because it's noon, because food is in front of you, or because friends are gathering for pizza, even if your body doesn't need food.

People are also motivated by a need to belong, to form and keep close relationships. Being included raises mood, while being left out or ignored is distressing, which helps explain behaviors like conforming to fit in.