Laws of Behaviour

Mental models for product design

047Bias

The Planning Fallacy

People are usually overly-optimistic when estimating the time required to complete a task.

Why it matters

Interestingly, this is true even if the participant is aware of this bias. People routinely produce plans that are unrealistically close to best-case scenarios.

In product design, this is problematic when asking users to complete a process (such as a lengthy sign-up), which goes on longer than they had anticipated .

Overconfidence creates churn.

Conversion rates:

• If a process is taking much longer than the user anticipated, they may just give up.

Input quality:

• The user may not give up, but instead rush their answers, or just select default options.

What to inspect

  • Check whether the experience reflects this: If a process is taking much longer than the user anticipated, they may just give up.
  • Check whether the experience reflects this: The user may not give up, but instead rush their answers, or just select default options.
  • Check whether the experience reflects this: In product design, this is problematic when asking users to complete a process (such as a lengthy sign-up), which goes on longer than they had anticipated .

Common anti-patterns

  • Assuming users consciously notice every place where "People are usually overly-optimistic when estimating the time required to complete a task" could apply.
  • Dense copy and parallel actions that increase mental effort unrelated to the user’s goal.
  • Ignoring downstream effects on effort & motivation when shipping this pattern.

Critique prompts

  • If a process is taking much longer than the user anticipated, they may just give up.
  • The user may not give up, but instead rush their answers, or just select default options.
  • In product design, this is problematic when asking users to complete a process (such as a lengthy sign-up), which goes on longer than they had anticipated .
  • Where on this screen would "The Planning Fallacy" show up as friction or misunderstanding?
  • What would a first-time user misunderstand here in under five seconds?

Related laws