Over justification effect:

The overjustification effect is a psychological phenomenon in which giving extrinsic rewards for behavior that was previously intrinsically rewarding can decrease a person's overall enjoyment and motivation for that activity. Essentially, when a person is rewarded for doing something they already enjoyed doing on its own, the intrinsic motivation may decrease as the extrinsic reward becomes the primary motivator.

This effect has been studied in various contexts, such as in schools where students are given rewards for things like reading or completing assignments, or in the workplace where employees receive bonuses for meeting certain goals. In these cases, the overjustification effect can lead to a decrease in the individual's interest and enjoyment in the activity over time.

One way to mitigate the overjustification effect is to provide rewards that are unexpected and not contingent on performance, or to ensure that intrinsic motivations are also nurtured and acknowledged alongside extrinsic rewards. It is important to strike a balance between extrinsic and intrinsic motivation to maintain long-term engagement and satisfaction.