While other theories of motivation support the belief that the cause of responses is internal, the incentive theory says that in fact the environment brings out behaviors.  The basic concept behind the incentive theory is goals.  When a goal is present, the person attempts to reach that goal.  The goal may be anything from relalxing to feeling stimulated to losing weight.  In order to relax, we may watch t.v.; in order to feel stimulated, we may skydive; in order to lose weight, we might go on an exercise preogram.
     Incentives may be tangible or intangible.  An intangible incentive may involve feeling good about oneself, while a tangible one may involve awards or something to give public recognition.  Intangible incentives are also known as intrinsic rewards, while tangible incentives are also known as extrinsic rewards.  Sometimes, one type of reward is replaced with the other.  This usually happens when an intrinsic reward is replaced with an extrinsic reward.  For instance, consider someone who becomes a doctor.  At first, the person may have become a doctor because he or she enjoys being able to help people (intrinsic); later on, however, the reason for being a doctor may change to money (extrinsic).  Suppose, however, that the hospital must have cutbacks, and they offer the doctor a choice: continue being a doctor and continue helping people but with a substantial pay cut, or become an administrator for somewhat more money than before.  The doctor would likely take the raise even though it would mean he or she wouldn’t be helping people anymore because the external reward of the increased pay would outweigh the internal reward of the satisfaction gained by helping people.  This situation is known as the overjustification effect.  In general, overjustification occurs when the external reward becomes the only reason for continuing a behavior.
     Educational psychologists are debating whether schools should use extrinsic rewards to encourage behavior.  There is evidence which suggests that it’s a bad idea because when the reward disappears, so does the children’s motivation.  The is also evidence, however, which suggests that it’s a good idea because the advantages gained by the extrinsic reward system may continue.