A meta-analytic review of experiments examining the effects of extrinsic rewards on intrinsic motivation.
Level 1 - systematic review of randomized trials
Meta-analysis of 128 experimental studies
PubMed 10589297 · doi:10.1037/0033-2909.125.6.627
What was done
A meta-analysis of 128 experimental studies evaluated the impact of extrinsic rewards on intrinsic motivation, assessing free-choice behavior and self-reported interest across reward contingencies (engagement-, completion-, and performance-contingent) and types (tangible, expected, verbal/positive feedback) in children and college students.
What was found
Extrinsic rewards significantly undermined free-choice intrinsic motivation for engagement-contingent (d = -0.40), completion-contingent (d = -0.36), and performance-contingent rewards (d = -0.28), as well as across all rewards, tangible rewards, and expected rewards. Self-reported interest was significantly undermined by engagement-contingent (d = -0.15) and completion-contingent rewards (d = -0.17), as well as all tangible and expected rewards. Conversely, positive feedback enhanced free-choice behavior (d = 0.33) and self-reported interest (d = 0.31). Tangible rewards tended to be more detrimental for children than college students, and verbal rewards were less enhancing for children.
Why it matters
This landmark synthesis demonstrates that tangible, expected rewards consistently diminish free-choice intrinsic motivation and interest, whereas informational verbal feedback enhances them.
Limits
The abstract does not report total participant counts, confidence intervals, or heterogeneity statistics. It does not provide data on long-term behavioral persistence beyond the experimental free-choice measure.