Overjustification effect
Paying people for something they already loved can crowd out the love.
What it means
The overjustification effect is the finding that providing a salient extrinsic reward for an activity that was already intrinsically motivating can reduce that intrinsic motivation, so that once the reward is withdrawn engagement often falls below its original level. The leading mechanism is a shift in perceived causality: people come to attribute their behavior to the external reward rather than to their own interest, in line with self-perception theory and self-determination theory's view that controlling incentives undermine autonomy. The effect depends on how the reward is experienced — rewards perceived as controlling are the ones that crowd out interest, whereas unexpected, performance-contingent, or informational rewards that signal competence can leave motivation intact or even enhance it. It is therefore not a blanket warning against all incentives but a caution about a particular kind of reward applied to an already-loved activity. The original demonstrations involved children who lost enthusiasm for drawing after being paid for it. It matters because it shows that motivation can be a fragile, partly endogenous resource that poorly designed pay schemes, grades, and gamification can deplete.
Examples
Children who loved drawing drew less, and with less evident joy, after being paid to draw and then having the payment stop.
A neighbour who has driven people to appointments for years, unpaid, is offered a small hourly fee and starts weighing whether the trip is worth the money. The favour has become a badly paid job.
An amateur baker handed an unexpected ribbon at the village show bakes more than ever. A reward that arrives afterwards and says 'you're good at this' informs rather than controls, so nothing gets crowded out.
First described in Lepper, Greene & Nisbett (1973).