UX Laws & Principles
Research-backed UX laws, principles, and methods connected to real insights
Accot-Zhai Steering Law
### Human physiology Moving a cursor along a long, straight line is physically difficult for humans due to the physiology of our elbows and wrists. As a result, the longer the motion, the greater the chance of error.
Aesthetic-Usability Effect
Users often perceive aesthetically pleasing design as more usable and are more tolerant of minor usability issues in beautiful interfaces.
Campbell's Law
The more important a metric is in social decision making, the more likely it is to be manipulated. ### Optimisation People tend to optimize their behavior to improve a metric when it's used to determine success or failure, sometimes leading to ridiculous or dangerous results that impact the overall user experience. It's critical that we use data as a tool to assist in decision making instead of allowing metrics alone to determine a decision. ### Limitation Metrics cannot fully and accurately describe the world. Every metric collected reflects a decision about what is considered important. ### Combination The combination of quantitative metrics with qualitative data enables us to better understand the consequences of design decisions. Without this combination, consequences may be missed by relying on passively collected analytics data.
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.
Fitts' Law
The time required to move to a target area is a function of the distance to the target and the size of the target.
Goal-Gradient Effect
The tendency to approach a goal increases with proximity to the goal. People accelerate their behavior as they get closer to achieving a goal.
Hick's Law
The time it takes to make a decision increases with the number and complexity of choices.
Jacob'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.
Law of Closure
People tend to perceive incomplete shapes or forms as complete by filling in the gaps with their mind.
Law of Common Region
Elements located within the same closed region are perceived as grouped together.
Law of Continuity
Elements arranged in a line or curve are perceived as more related than elements not on the line or curve. The eye tends to follow smooth, continuous paths.
Law of Proximity
Objects that are close to one another tend to be grouped together and perceived as a unit.
Law of Prägnanz
People will perceive and interpret ambiguous or complex images in the simplest form possible. Also known as the Law of Simplicity or Law of Good Figure.
Law of Similarity
Elements that share similar visual characteristics (color, shape, size, etc.) are perceived as related and grouped together.
Law of Uniform Connectedness
Elements that are visually connected (through lines, colors, shapes, or other visual links) are perceived as more related than elements that are not connected.
Miller's Law
The average person can only keep 7±2 items in their working memory.
Occam's Razor
Among competing hypotheses, the one with the fewest assumptions should be selected. In design, simpler solutions are usually better than complex ones.
Paradox of the Active User
Active users prefer to spend minimal time learning about a system, even if it means working less efficiently in the long run.
Pareto Principle
For many events, roughly 80% of the effects come from 20% of the causes. Also known as the 80/20 rule.
Parkinson's Law
Work expands to fill the time available for its completion.
Peak-End Rule
People judge an experience largely based on how they felt at its peak (most intense point) and at its end, rather than the total sum or average of every moment of the experience.
Postel's Law
Be conservative in what you send, be liberal in what you accept. Also known as the Robustness Principle.
Serial Position Effect
Users have a propensity to best remember the first and last items in a series.
Simon Effect
People respond faster and more accurately when the location of a stimulus matches the location of the response, even when stimulus location is irrelevant to the task.
Stroop Effect
The delay in reaction time when the name of a color is printed in a color not denoted by the name, demonstrating that automatic reading can interfere with color identification.
Tesler's Law
For any system, there is a certain amount of complexity that cannot be reduced. This complexity must be handled by either the system or the user.
The Principle of Least Effort
People will naturally choose the path of least resistance when completing tasks. Users tend to use the most convenient method available, even if it's not the most efficient.
Von Restorff Effect
Items that stand out from their surroundings are more likely to be remembered than items that blend in. Also known as the Isolation Effect.
Zeigarnik Effect
People remember interrupted or incomplete tasks better than completed tasks.
About UX Laws
UX Laws connect theoretical principles with real research insights. Each law is linked to supporting research findings from usability studies, helping you make evidence-based design decisions.