Why do we do the things we do? What drives our behavior? Psychologists have suggested different ways of thinking about motivation （动机）, including looking at whether motivation arises from outside （extrinsic） or inside （intrinsic） a person.
Researchers have found that each type has a different effect on a person's behavior and efforts to achieve goals. To better understand the influence of intrinsic and extrinsic motivation on human behavior, it would help to learn how each type works.
Extrinsic motivation is when you are motivated to perform a behavior or take part in an activity because you want to get a reward （奖赏）or avoid punishment. You will take action not because you enjoy it, but because you expect to get something in return or avoid something unpleasant.
Intrinsic motivation is when you decide to do something because you find it satisfying. You are performing an activity for what it is not because you are after some external （外部的）reward. The behavior itself is its own reward.
Studies have shown that offering too many external rewards for an already internally rewarding behavior can reduce intrinsic motivation—which is known as the over justification （奖励过当）effect. For example, in a 2008 study, children who were rewarded for playing with a toy they had already expressed interest in playing with became less interested in the toy after being externally rewarded.
This is not to suggest that extrinsic motivation is a bad thing—it can be beneficial in some situations. For example, extrinsic motivation can be especially helpful when a person needs to complete a task that they find unpleasant.
Most people would accept that intrinsic motivation is best, but it is not always possible in every situation. Sometimes a person simply has no internal wish to join in an activity.
Both extrinsic and intrinsic motivation play a key role in learning. Experts have argued that education's traditional stress on external rewards （such as grades, report cards, and gold stars） undermines any intrinsic motivation that students might already have. However, others have suggested that extrinsic motivators can help students feel more knowledgeable in the classroom, which in turn builds up their intrinsic motivation.
As professor David Myers put it, a person5s interest often survives when a reward is used neither to bribe （贿赂）nor to control but to show a job well done, as in a "most improved player" award. Put simply, rewards, rightly given, can increase enjoyment and motivate high performance.
Understanding how each type of motivation works and when it is likely to be useful can help people perform tasks and improve their learning.
