This effect occurs when a person’s intrinsic interest in a previously unrewarded activity is decreased as a result of engaging in that activity as a means to an extrinsic goal (e.g., financial reward) (Deci et al., 1999).
Deci, E. L., Koestner, R., & Ryan, R. M. (1999). A meta-analytic review of experiments examining the effects of extrinsic rewards on intrinsic motivation. Psychological Bulletin, 125, 627-668.