homeostasis

Meaning: Homeostasis is the maintenance of a relatively stable internal state, such as body temperature, blood glucose, and fluid balance, around a set point. In psychology it underlies drive reduction theory: a physiological need creates a drive, an unpleasant state of tension, and behavior that reduces the drive restores balance. Biology uses the same word for negative feedback regulation of physiological variables.

On the MCAT: A motivation passage asks which theory fits a behavior. Eating when hungry, drinking when thirsty, or seeking warmth when cold fit drive reduction. Curiosity, exploration, and thrill-seeking raise arousal instead of lowering a drive, so arousal theory (optimal arousal, Yerkes-Dodson) or incentive theory is the better fit. Primary drives are biological; secondary drives, such as the drive for money, are learned through association.

Common confusion: Homeostasis does not mean a fixed value. Variables fluctuate around a set point and are corrected by feedback. The drive is the motivating tension that appears when balance is disturbed, while homeostasis is the state being restored. Drive reduction theory also does not account for every kind of motivation, which is why the exam pairs it with other theories.