Fitts's law

The time to hit a target depends on its size and distance.

Fitts (1954), The information capacity of the human motor system in controlling the amplitude of movement.

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What is Fitts's law?

Fitts's law is a behavioural design principle (principle family): the time to hit a target depends on its size and distance. Big, close buttons get tapped; small, distant links get missed. Nudgeswipe rates the evidence as strong. Source: Fitts (1954), The information capacity of the human motor system in controlling the amplitude of movement.

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The research

Big, close buttons get tapped; small, distant links get missed.

● Strong evidence

This is a principle, not a bias. It relies on Friction (principle).

Source: doi.org/10.1037/h0055392

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Key takeaways

Honest nudge
Make primary and destructive actions appropriately sized and placed.
Dark-pattern line
Making "decline" or "unsubscribe" tiny and far from the thumb while "accept" is huge.

Use it

Apply this with your agent

The prompt carries this bias, its evidence rating and the honest-vs-dark line.

You are helping me apply a behavioural bias ethically in my product.

Bias: Fitts's law (Principle, strong evidence): The time to hit a target depends on its size and distance.
How it works: Big, close buttons get tapped; small, distant links get missed.
Source: Fitts (1954), The information capacity of the human motor system in controlling the amplitude of movement. https://doi.org/10.1037/h0055392
Honest use: Make primary and destructive actions appropriately sized and placed.
Dark-pattern line: Making "decline" or "unsubscribe" tiny and far from the thumb while "accept" is huge.
Page: https://nudgeswipe.com/biases/fitts-law/ (JSON: https://nudgeswipe.com/api/biases/fitts-law.json)

Rules: say a brand "uses" a tactic, never that it "worked"; outcomes are not public unless the company published them; no invented uplift estimates; flag mixed evidence. Honest nudge = true, visible, easy to reverse, and in the user's interest. Dark pattern = hides costs, fakes scarcity or popularity, shames, or makes leaving harder than joining. Quote company-published results as "X reports", with the source link, and don’t generalise them. Don’t cite retracted or failed-to-replicate studies as support (e.g. Ariely & Wertenbroch 2002). Don’t state study figures unless they’re on this page or in a source you can link. If an idea crosses the line, link the matching deceptive.design pattern.

Tasks:
1. Ask me for my product, the flow and the goal.
2. Audit where fitts's law already shapes that flow, for better or worse.
3. Propose 2-3 ethical experiments: hypothesis, variant, primary metric, guardrail metric.
4. Flag dark-pattern risks.

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Frequently asked questions

What is Fitts's law?

Fitts's law is a behavioural design principle: the time to hit a target depends on its size and distance.

How does Fitts's law work?

Big, close buttons get tapped; small, distant links get missed.

How strong is the evidence for Fitts's law?

Nudgeswipe rates it strong evidence. Original source: Fitts (1954), The information capacity of the human motor system in controlling the amplitude of movement.

How can you use Fitts's law honestly?

Make primary and destructive actions appropriately sized and placed.

When does Fitts's law become a dark pattern?

Making "decline" or "unsubscribe" tiny and far from the thumb while "accept" is huge.

In the wild

No teardown yet

We haven't captured a real product or email using fitts's law yet. Seen one? Use the prompt above to audit your own flow, or browse all teardowns.

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