UX laws explained.Ten principles, tested on real pages.
Each law here comes from research into how people see, decide and remember. For every one: what it says, what breaking it looks like on a website, and whether ProCurveUX can measure it or a person has to judge it.
What each law says, and how we check it.
A law is only as useful as the change it leads to. Where an automatic check exists, the card names it exactly as it appears in a ProCurveUX report.
- 01Paul Fitts, 1954
Fitts's law
The time it takes to hit a target depends on how far away it is and how big it is. Small, distant targets are slow and easy to miss.
On a websiteA 16px "×" in the corner of a mobile pop-up. People tap the page behind it, or give up and leave.
How ProCurveUX checks itChecked automatically- Target size below minimum
- Tap targets too small for a thumb
Every control is measured. Under 24×24 CSS pixels fails WCAG 2.2; under 44×44 is flagged as below the recommended size for touch.
- 02William Hick, 1952, and Ray Hyman, 1953
Hick's law
The more options people are shown at once, the longer they take to choose one.
On a websiteA hero with "Start free trial", "Book a demo", "Watch video" and "See pricing", all styled the same. Visitors stall instead of picking.
How ProCurveUX checks itPartly automatic- Competing primary calls to action
- Navigation does not collapse on a phone
Flags buttons of equal weight competing in one area, and phone navigation that shows six or more links at once. Whether a menu has too many items overall is a judgement call.
- 03Jakob Nielsen, 2000
Jakob's law
People spend most of their time on other websites, so they expect yours to work the way those do.
On a websiteA logo that does not link home, or a basket icon on the left. Visitors look where every other shop puts it and find nothing.
How ProCurveUX checks itPartly automatic- Inconsistent interaction pattern for the same task
- Current location not indicated in navigation
Checks that your site is consistent with itself and shows people where they are. Whether it matches conventions on other sites is left for a person to review.
- 04George Miller, 1956
Miller's law
People can hold only a few items in working memory at once. Miller suggested about seven; later research puts it closer to four chunks.
On a websiteA sign-up form with 14 fields in one long column, or a phone number shown as 03001234567 instead of 0300 123 4567.
How ProCurveUX checks itPartly automatic- Content wall without structure
- Form asks for information not required by the task
Flags long runs of text with no headings or breaks, and forms asking for more than the task needs. How well content is chunked beyond that needs a person.
- 05Gestalt psychologists, 1920s
Gestalt law of proximity
Things that sit close together are seen as belonging together.
On a websiteA field label spaced evenly between two inputs. Readers cannot tell which field it names.
How ProCurveUX checks itChecked automatically- Insufficient whitespace around dense content
- Alignment drift
Measures the gaps between groups against the gaps inside them, and flags edges that almost line up but do not.
- 06Hedwig von Restorff, 1933
Von Restorff effect
When several similar things are shown, the one that differs is the one people notice and remember.
On a websiteA primary "Buy now" button drawn with the same outline as "Add to wishlist". Nothing stands out, so nothing gets clicked first.
How ProCurveUX checks itChecked automatically- Button hierarchy not visually separable
- Visual hierarchy inverted
Compares the visual weight of primary and secondary actions, and flags a page where secondary content outweighs the primary.
- 07Larry Tesler, 1980s
Tesler's law
Every task has some complexity that cannot be removed. The only question is whether the product or the person deals with it.
On a websiteA checkout that asks for card type when it could tell from the first digits of the number.
How ProCurveUX checks itNeeds a person- Form asks for information not required by the task
Mostly a judgement call, flagged for manual review. The nearest automatic check catches forms that ask for fields the task does not need.
- 08Walter Doherty and Ahrvind Thadani, IBM, 1982
Doherty threshold
People stay engaged when a system responds in under about 400 milliseconds. Slower than that, attention drifts.
On a websiteA "Submit" button that shows nothing for two seconds. People click again and send the form twice.
How ProCurveUX checks itChecked automatically- Action without feedback
- Server is slow to answer
- First screen takes too long to paint
Clicks are watched for a visible response, and the server and first-paint times are measured in a real browser.
- 09Daniel Kahneman and colleagues, 1993
Peak-end rule
People judge an experience mostly by its most intense moment and by how it ended, not by the average.
On a websiteA smooth checkout that ends with shipping costs appearing on the last step. That surprise is what people remember.
How ProCurveUX checks itNeeds a person- Cost revealed only at the final step
How a whole journey feels is a judgement call, flagged for manual review. One bad ending is caught automatically: costs that first appear on the last step.
- 10Hermann Ebbinghaus, 1885
Serial position effect
People remember the first and last items in a list best, and the middle ones least.
On a websiteA nav that buries "Pricing" fifth of nine links, between items people skim past.
How ProCurveUX checks itNeeds a personNot checked automatically. Whether the most important items sit at the start and end of a list depends on your goals, so it is left for a person to review.
Laws are evidence, not commandments.
Most of these laws come from lab studies of reaction time and memory. They predict tendencies, not what every visitor will do. Use them to explain a problem you can see, not to win an argument about one you can’t.
When a law is marked “Needs a person”, ProCurveUX lists it in the report as a manual review item rather than guessing. For accessibility rules, see the WCAG 2.2 checklist, and for the reasoning behind the audit, read what an automated UX audit can really catch.
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