UX Runs on Psychology
Design decisions that feel like gut calls are usually the application - conscious or not - of documented psychological phenomena. The difference between a designer who guesses and one who creates reliably great experiences is an understanding of these laws.
Here are the ten that matter most.
1. Hick's Law The time it takes to make a decision increases with the number of options available. This is why every unnecessary navigation item, every superfluous CTA, every "just in case" feature you add costs the user time and cognitive load - and pushes them toward abandonment.
Application: Ruthlessly eliminate choices that don't serve a user's core task. Menus should be short. CTA buttons should be singular. Each page should have one job.
2. Fitts's Law The time to reach a target is a function of distance to and size of the target. Buttons that are too small or too far from where the user's cursor naturally rests are frustrating in ways users can't name but feel deeply.
Application: Make primary CTAs large and place them where the user's attention already is. Mobile tap targets should be a minimum of 44×44px.
3. Miller's Law Short-term memory can hold approximately 7 (±2) items at a time. Navigation menus with 11 items, forms with 20 fields, onboarding flows with 8 steps - all of these are asking users to hold more than the brain comfortably manages.
Application: Chunk content into groups of 5-7. Break long forms into multi-step flows. Progressive disclosure is your friend.
4. Jakob's Law Users spend most of their time on other websites. They expect yours to work like those. Radical novelty in navigation patterns is almost always a liability, not a differentiator.
Application: Be distinctive in your visual design, not in your UX patterns. Innovation in layout often means confusion in practice.
5. The Aesthetic-Usability Effect Users perceive aesthetically pleasing designs as more usable. This means a beautiful design earns goodwill that can carry users through moments of friction - while an ugly design will be blamed for problems it didn't cause.
Application: Visual quality is a UX investment, not just a brand investment. Don't let "it works" be the bar.
6. The Von Restorff Effect (Isolation Effect) When multiple similar objects are present, the one that differs will be remembered. This is why a single coloured button in a field of grey text stands out - and why using too many coloured elements neutralises all of them.
Application: Reserve visual emphasis for what matters most. Contrast only works when it's scarce.
7. The Zeigarnik Effect People remember uncompleted tasks better than completed ones. Progress bars and completion indicators leverage this - they create a sense of incompleteness that motivates users to finish.
Application: Use progress indicators in onboarding flows, multi-step checkouts, and profile completion. Show users how far they've come.
8. Peak-End Rule People judge an experience primarily by how it felt at its most intense moment and how it ended - not the average. A brilliant checkout experience after a mediocre product discovery will be remembered as good.
Application: Invest in the moments that matter most (final CTA, checkout completion, post-purchase screen) disproportionately to the rest.
9. Doherty Threshold Productivity soars when a computer and user interact at a pace of under 400ms. Users disengage when systems are slow, and they rarely come back.
Application: Perceived performance matters as much as real performance. Use skeleton loaders, optimistic UI updates, and lazy loading to keep things feeling fast even when they aren't.
10. Tesler's Law (Law of Conservation of Complexity) Every application has an inherent complexity that cannot be removed - only transferred. Either the designer absorbs it (making the interface simple) or the user absorbs it (making their experience complicated).
Application: Every time a form field is removed, a default is set, or a process is automated, you're paying a design tax so your user doesn't have to.
