drive

Meaning: In drive-reduction theory (Clark Hull), a physiological need creates a drive, an uncomfortable state of tension that motivates behavior. When the behavior lowers the tension, the drive is reduced, homeostasis is restored, and the behavior is reinforced. Primary drives come from biological needs (hunger, thirst, need for warmth). Secondary drives are learned by association with primary ones, as when money becomes motivating because it buys food. The stronger the unmet need, the stronger the drive.

On the MCAT: Passages describe a motivated behavior and ask which theory explains it. Eating after a long fast, or drinking after exertion, fits drive reduction. Behavior that seeks stimulation without any deficit, such as exploring or thrill seeking, is usually explained by arousal theory (organisms seek an optimal level of arousal, linked to Yerkes-Dodson). Behavior pulled by an external reward, such as a trophy, fits incentive theory. Questions may also contrast drives with instincts or place them within Maslow's hierarchy.

Common confusion: A need is the physiological deficit, and a drive is the psychological push it produces. A drive also pushes from inside, while an incentive pulls from outside. Drive reduction cannot account for behavior that raises tension, which is why the exam presents arousal and incentive theories as alternatives or supplements.