The Lepper, Greene and Nisbett experiment: the foundational demonstration

Lepper, Greene and Nisbett’s (1973) study is the definitive empirical demonstration of the overjustification effect. Children who showed genuine intrinsic interest in a drawing activity were divided into three conditions: one group was promised a reward for drawing, one received an unexpected reward after drawing, and one received no reward. When subsequently observed during free play, the children who had been promised and received the expected reward showed significantly reduced interest in the drawing activity — despite their prior genuine interest. The unexpected reward group and the no-reward group maintained their interest.

The critical feature of the design is that the promised reward group’s prior intrinsic motivation was genuine — the drawing was genuinely enjoyed before the reward was introduced. The reduction was not compensation for low initial interest; it was a genuine undermining of prior genuine interest. The mechanism Lepper et al. proposed: the expectation of the reward provided the most salient available explanation for the drawing behaviour, making the internal explanation — “I draw because I enjoy drawing” — less necessary and less available.

The name overjustification captures this precisely: the reward overjustifies the behaviour. It provides a salient external reason for doing something the person already had an internal reason to do. When the external reason becomes the most obvious explanation, the internal one fades as a functional motivator.

The 128-study meta-analysis: the evidence at scale

Deci, Koestner and Ryan’s (1999) meta-analysis of 128 controlled experiments confirmed the foundational finding at scale: tangible, expected, contingent rewards reliably undermine intrinsic motivation for the rewarded activity. The meta-analysis also established the finding’s most important implication for understanding motivation: intrinsic and extrinsic motivation are not additive. Adding external motivation to existing internal motivation does not produce more total motivation; it shifts the motivational orientation from internal to external, with predictable consequences for the quality, creativity, and durability of the resulting behaviour.

The orientation of motivation — whether the behaviour is intrinsically or extrinsically motivated — is more important than the total amount of motivation for predicting behaviour and its consequences. This is the finding that most directly challenges the conventional assumption about incentive design: more incentive does not produce proportionally more or better behaviour. It can produce less, and specifically worse, if it shifts the motivational orientation in the wrong direction.

Cognitive evaluation theory: the locus of causality mechanism

Deci and Ryan’s (2000) cognitive evaluation theory provides the precise mechanism through which rewards undermine intrinsic motivation. When intrinsically motivated, the perceived locus of causality for the behaviour is internal: “I am doing this because I choose to and because I find it meaningful.” The introduction of a salient, expected, contingent external reward shifts the perceived locus of causality from internal to external: “I am doing this because of the reward.” The activity becomes a means to the reward rather than an end in itself.

The shift is not primarily a conscious re-evaluation. It is the automatic attribution process that the salience of the external reward drives. The reward becomes the most available explanation for the behaviour — more immediately salient than the internal motivation that preceded it — and the internal explanation recedes as a consequence.

For the entrepreneur, this mechanism has specific implications for incentive design that are systematically underappreciated in business culture. The performance bonus, the revenue milestone celebration, and the commission structure that are intended to sustain motivation may, if they are expected, contingent, and perceived as controlling, be progressively converting the intrinsically motivated work of building something meaningful into extrinsically contingent performance. The conversion is gradual, invisible from the inside, and ends in the motivational profile that the SDT burnout research documents as the endpoint of sustained controlled motivation: compliance without engagement, performance without care, and eventual exhaustion without replenishment.

The moderating conditions: when rewards are safe and when they are not

The research identifies specific conditions under which external rewards do not undermine intrinsic motivation. Unexpected rewards — given after the task is completed, without prior contingency — do not shift the perceived locus of causality because they are not the most available explanation for the behaviour that produced them. Informational feedback — rewards that communicate competence (“this is excellent work”) rather than control (“you did this because we required it”) — can enhance intrinsic motivation by supporting the perceived competence that is one of its psychological prerequisites.

The contingency is the critical variable: expected, contingent, controlling rewards undermine; unexpected, non-contingent, informational rewards do not. For the entrepreneur designing their incentive environment, the distinction generates specific design principles. Celebrating the quality and process of building — acknowledging specific competence, genuine contribution, and the work’s intrinsic meaning — preserves intrinsic motivation. Structuring acknowledgement primarily around revenue outcomes — where the most salient fact about the work is whether it hit the number — shifts the motivational orientation toward the number as the work’s purpose.

The identified regulation alternative

The SDT continuum that Deci and Ryan’s (2000) research programme established provides the practical alternative to the intrinsic-versus-extrinsic binary for entrepreneurial contexts where external metrics are genuinely unavoidable. Identified regulation is the genuine endorsement of external goals as personally meaningful — not performing motivation toward them, but actually believing in why they matter. The entrepreneur who can genuinely identify with why the revenue goal matters — because revenue funds the mission, because sustainable revenue enables long-term impact, because commercial viability is the mechanism through which the work continues — is operating from identified regulation that maintains motivational quality despite the presence of external metrics.

The distinction from introjected regulation — pursuing the goal to avoid shame or because “I should” — is the presence of genuine endorsement. Identified regulation preserves the autonomy dimension that cognitive evaluation theory identifies as the prerequisite for high-quality motivation. Introjected regulation, while internalised, is still controlled: the motivation remains contingent on the external standard rather than on genuine engagement with the work’s meaning.

Books worth reading on this

Punished by Rewards by Alfie Kohn is the most thorough available popular account of the overjustification effect and its institutional implications — covering the experimental evidence across education, business, and parenting, the specific conditions under which rewards undermine rather than enhance the behaviours they are intended to produce, and the institutional habits that persist despite this evidence because they feel intuitively correct. Kohn’s account of why the belief that more reward produces more motivation is so resistant to the evidence against it, and his specific account of what the evidence supports as an alternative approach to motivation design, makes this the most comprehensive available popular treatment of the Lepper and Deci research programmes for an audience concerned with practical application.

If the dynamics described here are significantly affecting your wellbeing, speaking with a psychologist is the right next step. UK: Samaritans (116 123, free, 24/7). Mind (0300 123 3393). BACP: bacp.co.uk/search/Therapists. Crisis Text Line — text HOME to 741741 (US, UK, Canada, Ireland). International: internationaltherapistdirectory.com.

This article is for educational and informational purposes only. Sources: Lepper, M.R., Greene, D. & Nisbett, R.E. (1973), Undermining Children’s Intrinsic Interest with Extrinsic Reward, Journal of Personality and Social Psychology, 28(1), 129–137. Deci, E.L. (1971), Effects of Externally Mediated Rewards on Intrinsic Motivation, Journal of Personality and Social Psychology, 18(1), 105–115. 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. Deci, E.L. & Ryan, R.M. (2000), The “What” and “Why” of Goal Pursuits, Psychological Inquiry, 11(4), 227–268. Ryan, R.M. & Deci, E.L. (2000), Self-Determination Theory and the Facilitation of Intrinsic Motivation, American Psychologist, 55(1), 68–78. Kohn, A. (1993), Punished by Rewards, Houghton Mifflin. Pink, D. (2009), Drive, Riverhead Books.