Motivation and emotion help guide our behavior. Motives are specific inner needs or wants that arouse an organism and direct its behavior toward a goal. Emotions are experiences of feelings such as fear, joy, or surprise, which also underlie behavior.

At the turn of the twentieth century, psychologists believed that motivated behavior was caused by instincts, specific, inborn behavior patterns characteristic of a species. Drive-reduction theory viewed motivated behavior as a strategy to ease an unpleasant state of tension or arousal (a drive) and return the body to a state of homeostasis, or balance. Today scientists assert that an organism seeks to maintain an optimum state of arousal. External stimuli called incentives also prompt goal-oriented behavior. Finally, motivation can be intrinsic (coming from within the individual) or extrinsic (for external reward or avoidance of punishment).