UX Laws

UX Laws is a collection of best practices that designers can consider when building user interfaces.

Cognitive Bias

Peak-End Rule

People judge an experience largely based on how they felt at its peak and at its end, rather than the total sum or average of every moment of the experience.

Cognitive Bias

Serial Position Effect

Users have a propensity to best remember the first and last items in a series.

Cognitive Bias

Von Restorff Effect

The Von Restorff effect, also known as The Isolation Effect, predicts that when multiple similar objects are present, the one that differs from the rest is most likely to be remembered.

Cognitive Bias

Zeigarnik Effect

People remember uncompleted or interrupted tasks better than completed tasks.

Gestal

Law of Common Region

Elements tend to be perceived into groups if they are sharing an area with a clearly defined boundary.

Gestal

Law of Proximity

Objects that are near, or proximate to each other, tend to be grouped together.

Gestal

Law of Prägnanz

People will perceive and interpret ambiguous or complex images as the simplest form possible, because it is the interpretation that requires the least cognitive effort of us.

Gestal

Law of Similarity

The human eye tends to perceive similar elements in a design as a complete picture, shape, or group, even if those elements are separated.

Gestal

Law of Uniform Connectedness

Elements that are visually connected are perceived as more related than elements with no connection.

Principle

Doherty Threshold

Productivity soars when a computer and its users interact at a pace (<400ms) that ensures that neither has to wait on the other.

Principle

Occam’s Razor

Among competing hypotheses that predict equally well, the one with the fewest assumptions should be selected.

Principle

Pareto Principle

The Pareto principle states that, for many events, roughly 80% of the effects come from 20% of the causes.

Principle

Postel’s Law

Be liberal in what you accept, and conservative in what you send.

Principle

Tesler’s Law

Tesler’s Law, also known as The Law of Conservation of Complexity, states that for any system there is a certain amount of complexity which cannot be reduced.

Heuristic

Parkinson’s Law

Any task will inflate until all of the available time is spent.

Heuristic

Miller’s Law

The average person can only keep 7 (plus or minus 2) items in their working memory.

Heuristic

Jakob’s Law

Users spend most of their time on other sites. This means that users prefer your site to work the same way as all the other sites they already know.

Heuristic

Hick's Law

The time it takes to make a decision increases with the number and complexity of choices.

Heuristic

Goal-Gradient Effect

The tendency to approach a goal increases with proximity to the goal.

Heuristic

Aesthetic-Usability Effect

Users often perceive aesthetically pleasing design as design that’s more usable.

Heuristic

Fitts’s Law

The time to acquire a target is a function of the distance to and size of the target.