Overjustification Effect

The overjustification effect refers to the idea that when engaging in an activity, a subject who is aware of an external motivation (reward) for the activity, will be less motivated.

Source:

Rozin, Paul (1988). “Social Learning About Food by Humans. In T. R. Zentall & B. Galef (Eds.), Social learning: Psychological and biological perspectives” (180–182). Hillsdale, NJ:Lawrence Erlbaum Associates.