Motivation psychology; social psychology; behavioral science

Deci Effect

Use rewards carefully: pay fairly, but do not turn an already meaningful or enjoyable activity into something people do only for a prize.

Popularity

Usefulness

Aliases

Reward-Undermining Effect / Undermining Effect of Extrinsic Rewards / Overjustification Effect / Extrinsic Rewards and Intrinsic Motivation

Domains

Education, management, parenting, coaching, product design, gamification, creative work

Definition

The Deci Effect refers to the tendency for expected external rewards, especially tangible or controlling rewards, to reduce a person’s later intrinsic motivation for an activity that they already find interesting. In academic literature, it is usually discussed as the undermining effect of extrinsic rewards, overjustification effect, or within cognitive evaluation theory and self-determination theory.

Rewards are not always motivational in the long run. When a reward makes a person feel that they are doing an activity “for the reward” rather than because they choose or enjoy it, intrinsic motivation can decline. Rewards or feedback that support competence and autonomy may avoid this problem or sometimes increase motivation. (Self-Determination Theory)

A person initially finds an activity interesting or satisfying.
An external reward is introduced, especially one that is expected, tangible, or tied to doing the task.
The person may reinterpret their reason for acting: from “I enjoy this” to “I am doing this to get the reward.”
This can reduce perceived autonomy and shift motivation toward external control.
When the reward is removed, voluntary engagement may drop below the original level.
The effect is weaker or may not apply when rewards are unexpected, informational, autonomy-supporting, or used for tasks with little initial intrinsic interest. (Self-Determination Theory)

A child enjoys drawing. Parents begin paying the child for every drawing. At first, the child draws more, but later may draw less when no payment is offered. A better approach is to praise effort and improvement, provide choice, and avoid making the activity feel like paid labor.

Example: Edward L. Deci’s 1971 Soma puzzle experiments. Participants worked on interesting puzzles across multiple sessions. In the reward condition, participants received money during one session but not later. Deci reported that monetary reward tended to decrease later intrinsic motivation, while verbal reinforcement and positive feedback tended to increase it.
Why it fits this rule: The experiment directly tested whether an external reward changes people’s voluntary interest in an activity after the reward is removed.
Verification status: Verified as a published 1971 study in Journal of Personality and Social Psychology. The general reward-undermining effect is supported by later reviews and meta-analysis, but its size and boundaries depend on reward type, task type, and context. (PubMed)

Designing classroom reward systems without damaging curiosity.
Managing creative or knowledge workers without turning every task into a transaction.
Building gamified apps where badges, points, or streaks might crowd out genuine interest.
Parenting and coaching, especially when a child already enjoys the activity.
Encouraging long-term learning, reading, coding, music, art, or problem-solving.

Do not interpret it as “all rewards are bad.”
Do not use it as an excuse to underpay people; fair compensation is separate from preserving intrinsic motivation.
Do not apply it strongly to boring or low-interest tasks where external incentives may be useful.
Do not reduce the effect to “large rewards are bad.” The key issue is often whether the reward feels controlling, expected, and task-contingent.
Do not assume praise is always good; praise can also feel controlling if it pressures performance rather than supporting competence.

Invented by: Not formally invented as a universal “law.” It is associated with Edward L. Deci’s research on external rewards and intrinsic motivation.
Year of invention: No single formal invention year. The key origin is Deci’s 1971 paper, “Effects of Externally Mediated Rewards on Intrinsic Motivation.”
Country / context of origin: United States; experimental motivation research conducted at Carnegie-Mellon University, with Deci affiliated with the University of Rochester.

Deci’s 1971 paper reported two laboratory experiments and one field experiment on how external rewards affect intrinsic motivation. The paper reported that money tended to decrease intrinsic motivation, while verbal reinforcement and positive feedback tended to increase it.
Ryan and Deci’s 2000 review explains the effect through self-determination theory and cognitive evaluation theory: autonomy and competence support intrinsic motivation, while controlling rewards, deadlines, threats, and pressured evaluations can diminish it. (Self-Determination Theory)
Deci, Koestner, and Ryan’s 1999 meta-analysis reviewed 128 studies and found that several forms of expected tangible rewards undermined free-choice intrinsic motivation, while also noting that reward effects vary by type and context. (PubMed)

Use rewards carefully: pay fairly, but do not turn an already meaningful or enjoyable activity into something people do only for a prize.