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 design that’s more usable. ### Aesthetics An aesthetically pleasing design creates a positive response in people’s brains and leads them to believe the design actually works better than other, equally usable, (but less visually appealing) designs. ### Tolerance People are more tolerant of minor usability issues when the design of a product or service is aesthetically pleasing. ### Usability problems Visually pleasing design can mask usability problems and prevent issues from being discovered during usability testing.
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. ### System feedback Provide system feedback within 400 ms in order to keep users’ attention and increase productivity. ### Perceived performance Use perceived performance to improve response time and reduce the perception of waiting. ### Animation Animation is one way to visually engage people while loading or processing is happening in the background. ### Progress bars Progress bars make wait times tolerable, regardless of their accuracy. ### Purposeful delay Purposefully adding a delay to a process can actually increase its perceived value and instill a sense of trust, even when the process itself actually takes much less time.
Fitts' Law
The time to acquire a target is a function of the distance to and size of the target. ### Size Touch targets should be large enough for users to accurately select. ### Spacing Touch targets should have ample spacing between them. ### Placement Touch targets should be placed in areas of an interface that allow them to be easily accessed.
Goal-Gradient Effect
The tendency to approach a goal increases with proximity to the goal. ### Proximity is an accelerant The closer users are to completing a task, the faster they work towards reaching it. ### Motivate Providing artificial progress towards a goal will help to ensure users have the motivation to complete that task. ### Progress Provide a clear indication of progress in order to motivate users to complete tasks.
Hick's Law
The time it takes to make a decision increases with the number and complexity of choices. ### Minimize choices Minimize choices when response times are critical to decrease decision time. ### Smaller steps Break complex tasks into smaller steps in order to decrease cognitive load. ### Provide recommendations Avoid overwhelming users by highlighting recommended options. ### Progressive onboarding Use progressive onboarding to minimize cognitive load for new users. ### Simplification Be careful not to simplify to the point of abstraction.
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.
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. ### Expectations Users will transfer expectations they have built around one familiar product to another that appears similar. ### Existing mental models By leveraging existing mental models, we can create superior user experiences in which the users can focus on their tasks, rather than on learning new models. ### Minimize discord When making changes, minimize discord by empowering users to continue using a familiar version for a limited time.
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 tend to be perceived into groups if they are sharing an area with a clearly defined boundary. ### Structure and relationship Common region creates a clear structure and helps users quickly and effectively understand the relationship between elements and sections. ### Borders Adding a border around an element or group of elements is an easy way to create common region. ### Backgrounds Common region can also be created by defining a background behind an element or group of elements.
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 near to, or proximate to each other, tend to be grouped together. ## Relationship Proximity helps to establish a relationship with nearby objects. ## Perception Elements in close proximity are perceived to share similar functionality or traits. ## Organizing information Proximity helps users understand and organize information faster and more efficiently.
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. ### Simplicity and order The human eye likes to find simplicity and order in complex shapes because it prevents us from becoming overwhelmed with information. ### Visual processing Research confirms that people are better able to visually process and remember simple figures than complex figures. ### Unified shape The human eye simplifies complex shapes by transforming them into a single, unified shape.
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.