The westerner effect holds that a moderate reward is conducive to consolidating the individual's intrinsic motivation, but too many rewards may reduce the individual's interest in the matter itself and its intrinsic motivation.

Desi found in the experiment that in some cases, when people have both external rewards and internal rewards, they will not only enhance their work motivation, but will reduce their work motivation. At this point, the intensity of motivation will become the difference between the two. People call this law the Desi effect. This result shows that if external material rewards (plus rewards) (that is, internal rewards) are provided for a pleasant activity, the attraction of this activity to participants will be reduced.