The Overjustification Effect: Why Rewards Can Kill a Child's Love of Drawing, Reading and Learning

At the Stanford University nursery school, researchers unobtrusively observed free play for several days and selected 51 children aged 3–5 who spontaneously enjoyed drawing with markers. They were assigned to three groups:

1. Expected award: the child was promised a fancy "Good Player Award" certificate with a gold seal and ribbon for drawing.
2. Unexpected award: the child drew and received the same certificate without warning.
3. No award.

One to two weeks later, the markers were put back in the classroom, and researchers recorded how much time children spent drawing on their own, with no adults or rewards.

The key is not the reward itself but how children explain their own behavior. Drawing "for a certificate" turns play into work. Cognitive evaluation theory, part of Deci and Ryan's self-determination theory, later explained this: controlling rewards undermine the sense of autonomy. A meta-analysis of 128 studies confirmed the effect, especially in children (Deci et al., 1999). A similar result appeared even in 20-month-olds: after being rewarded for helping, they helped less (Warneken & Tomasello, 2008).

This matters when designing reward systems (stickers, token economies): they help with behavior a child finds uninteresting but can backfire where interest already exists. In parent guidance, explain the difference between controlling and informational rewards.