Review - A meta-analytic review of experiments examining the effects of extrinsic rewards on intrinsic motivation

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(6), 627–668. https:// https://doi.org/10.1037/0033-2909.125.6.627

Abstract:

A meta-analysis of 128 studies examined the effects of extrinsic rewards on intrinsic motivation. As predicted, engagement-contingent, completion-contingent, and performance-contingent rewards significantly undermined free-choice intrinsic motivation (d = -0.40, -0.36, and -0.28, respectively), as did all rewards, all tangible rewards, and all expected rewards. Engagement-contingent and completioncontingent rewards also significantly undermined self-reported interest (d = -0.15, and —0.17), as did all tangible rewards and all expected rewards. Positive feedback enhanced both 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 tended to be less enhancing for children than college students. The authors review 4 previous meta-analyses of this literature and detail how this study’s methods, analyses, and results differed from the previous ones.

Main arguments:

A meta-analytic review first reviewed three previous meta-analysis that confirmed the effects of extrinsic rewards undermining intrinsic motivation, two reporting different conclusions, and find the most consistent finding was that task-contingent tangible rewards were detrimental to intrinsic motivation. 128 studies were aggregated to examine different reward types’ effects on intrinsic motivation, with results for the free-choice behavioral measure and the self-reported interest measure. specifically, as predicted, engagement-contingent rewards, completion-contingent rewards, and performance-contingent rewards significantly undermined free-choice intrinsic motivation, as did all rewards, tangible rewards and all expected rewards.

The meta-analysis provide strong confirmation that positive feedback enhances intrinsic motivation, which is predicted by cognitive evaluation theory (GET, later evolved into Self-Determination Theory, SDT). Substantially different results from informational vs. controlling verbal reward were found as well as predicted.

Key takeaway:

Reward and contingency types:

• verbal (unexpected) reward
• unexpected tangible reward
• expected tangible reward: task-noncontigent, engagement-contingent, completion-contingent, performance-contingent

Common measures for intrinsic motivation:

• Free-choice behavior
• Self-reported interest

CET (Cognitive Evaluation Theory) predicts unexpected, non-controlled reward do not undermine intrinsic motivation, as not perceived as controlling the autonomy.

Task-contingent tangible rewards detrimental to intrinsic motivation

Expected tangible reward contingent on task performance undermine intrinsic motivation

Informational verbal rewards enhance intrinsic motivation

Autonomy, mastery, purpose are the end goals

Notes:

Chapter 8 of Reiss’ book of Myths of Intrinsic Motivation ¹ were devoted to counter argue this meta-analysis:

Publication bias: no undermining research tend not to be published

Ceiling effects: many studies were significantly biased in favor of finding undermining effects because they pre-selected people with high levels of interest and due to ceiling effects could not measure when rewards further increased intrinsic interest.

Tips for motivation literature review:

We began by searching the PsycINFO and ERIC databases and recent editions of the Current Contents database for studies published between 1971 and August 1997. Varying combinations of the following search terms were entered: intrinsic motivation, rewards, reinforcement, free time, and free choice.

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