Why do some apps feel intuitive from the first second, while others instantly frustrate us? The answer rarely lies in button colors, but in cognitive psychology.
UX laws aren't arbitrary rules invented by designers. They are scientific observations on how the human brain processes information, makes decisions, and interacts with the world.
"Everyone has their law... except you?! Don't worry, mastering others' laws is already a superpower."
Miller's Law
"The magical number 7, plus or minus 2"
In 1956, George Miller asserted that the average person's working memory can only hold about 7 items (±2) at a time.
💡 UX Application: Chunking
Don't overwhelm the user. Group information into logical "chunks".
- ✓Phone number: 06 61 23 45 67 (5 chunks of 2)
- ✗Phone number: 0661234567 (1 chunk of 10 = difficult)
Hick's Law
"Decision time increases with the number of choices"
The more options you give a user, the longer they will take to choose, and the higher the risk of abandonment (analysis paralysis).
❌ Bad Practice
A mega-menu with 50 links visible at once without hierarchy.
✅ Good Practice
A step-by-step onboarding process limiting choices at each screen.
Fitts's Law
"Size and distance matter"
The time required to rapidly move to a target area is a function of the ratio between the distance to the target and the width of the target. Simply put: make buttons big and close to the thumb!
🚀 Mobile Insight
On mobile, the "Thumb Zone" is critical. Main CTAs must be at the bottom of the screen, easily accessible, and have a minimum height of 44-48px (Apple/Google standard).
Jakob's Law
"Users spend most of their time on other sites"
Jakob Nielsen reminds us that users prefer your site to work the same way as all the other sites they already know.
Don't reinvent the wheel just for fun.
The search bar? A magnifying glass. The cart? A trolley in the top right. The logo? Back to home. Innovation must serve function, not confusion.
Law of Prägnanz
"The brain loves simplicity"
Faced with complex or ambiguous shapes, the human brain seeks to interpret them in the simplest way possible. It "fills in the gaps" to create meaning.
- 🔹 Minimalism: Less visual noise means clearer information.
- 🔹 Icons: A simple icon (3 lines for a menu) is instantly recognized as a whole.
- 🔹 Shapes: Use standard geometric shapes rather than complex abstract ones.
Occam's Razor
"The simplest solution is often the best"
In design, this means eliminating everything that isn't necessary. If an element doesn't help the user accomplish their task, it must go.
Less is More.
Goal Gradient Effect
"The closer you are, the faster you go"
A user's motivation increases as they get closer to their goal.
Practical Applications:
- 🚀 Progress Bars: Visually show advancement (e.g., "Step 3/4").
- 🎁 Loyalty Programs: A pre-stamped card is more effective than an empty one.
- 🛒 Checkout: Visualize remaining steps to encourage completion.
Aesthetic-Usability Effect
"Beautiful works better"
Users perceive aesthetically pleasing designs as being more usable. Good design creates a positive emotional response that makes the user more tolerant of minor usability issues.
Warning: this doesn't save a broken product, but it helps with adoption.
🎁 Bonus: 2 Lesser-Known but Powerful Laws
Zeigarnik Effect
People remember uncompleted or interrupted tasks better than completed tasks.
Usage: "Profile 80% complete" notifications or content teasers.
Doherty Threshold
Productivity soars when computer and user interact at a pace < 400ms.
Usage: Performance optimization (Core Web Vitals), skeletons loading, instant feedback.
Conclusion: Design is a Human Science
Knowing these laws doesn't stifle creativity; on the contrary. It's like knowing music theory for a musician: it gives the framework needed to compose digital symphonies that truly resonate with users.
At VOID, we don't apply these laws blindly; we use them to justify our choices and ensure every pixel has a reason for being.
Ready to Apply These Laws to Your Interface?
Since 2009, VOID has been helping major brands design high-performance interfaces. Banks, insurance companies, e-commerce: we apply these fundamental laws to transform your interfaces into conversion machines.
✓ Complete audit based on psychological laws
✓ Friction point identification
✓ Custom improvement roadmap