Laws of Behaviour

Mental models for product design

030Effect

Overjustification Effect

If users are being incentivised to complete a task, especially with money or 'rewards', they can be less motivated than they otherwise would be.

Why it matters

People are deeply motivated to do certain things because of their intrinsic value (i.e., how it makes them feel), rather than an obvious external benefit (like money).

For example, you may pick up litter that you see in the street, because you want a cleaner neighbourhood. But you may resent being paid to pick up litter.

The overjustification effect, explains how the 'incentive' distorts the original intent , despite objectively being the same task.

A more product-related example would be being financially incentivised to invite your friends to an app .

If you genuinely believe that they'd benefit from the service, sharing it is a well-intended act. Your incentive is to help your friend (and possibly making your experience better).

But if that same app paid you £3 for every referral, your friend's account has a value . You may perceive an invitation as being worth more than £3.

It may also feel disingenuous, despite being the same action.

What to inspect

  • Check whether the experience reflects this: For example, you may pick up litter that you see in the street, because you want a cleaner neighbourhood.
  • Check whether the experience reflects this: But you may resent being paid to pick up litter.
  • Check whether the experience reflects this: The overjustification effect, explains how the 'incentive' distorts the original intent , despite objectively being the same task.

Common anti-patterns

  • Assuming users consciously notice every place where "If users are being incentivised to complete a task, especially with money or 'rewards', they can be less motivated than they otherwise would be" could apply.
  • Dense copy and parallel actions that increase mental effort unrelated to the user’s goal.
  • Ignoring downstream effects on conversion rates when shipping this pattern.

Critique prompts

  • For example, you may pick up litter that you see in the street, because you want a cleaner neighbourhood.
  • But you may resent being paid to pick up litter.
  • The overjustification effect, explains how the 'incentive' distorts the original intent , despite objectively being the same task.
  • Where on this screen would "Overjustification Effect" show up as friction or misunderstanding?
  • What would a first-time user misunderstand here in under five seconds?

Related laws