Extrinsic rewards can crowd out intrinsic motivation.
The classic overjustification experiment was Lepper, Greene and Nisbett's in 1973, which found that expected rewards reduced preschoolers' later intrinsic interest in drawing; Amabile developed the related work on intrinsic motivation and creativity. The effect is strongest where the activity was already intrinsically rewarding.
In practice
- A volunteer who has run the village fete for eleven years is offered a small honorarium and resigns within two seasons.
- An open-source maintainer accepts sponsorship, starts thinking of the work as a job, and stops enjoying the parts nobody pays for.