15 Psychology Principles Every Designer Should Know

Psychology is a very extensive science, but as you probably already know, it is closely related to design. Good design without knowledge of psychology is rather the exception, not the rule.

Knowledge of psychology and basic principles of perception and behavior are the main allies of a good designer. In this article, we will single out and explain with examples the 15 most important psychological principles that every designer must know.

1. The effect of “aesthetics in usability”

The more aesthetic the design, the sooner it will be considered convenient.
The effect of “aesthetics on usability” was noticed in 1995 by researchers Masaaki Kurosu and Kaori Kashimura of the Hitachi Design Centre. They experimented and showed 26 ATM screen designs to 252 users and asked them to evaluate the convenience and beauty of each. It turned out that the more aesthetic the interface looked, the higher its functionality was rated.
Tumblr is a vivid example - its service is nice, but not very user-friendly. For example, the selection of interests in a profile looks chaotic. The layout is beautiful, but the selection button is dark and located outside a prominent view, and the top menu didn’t seem to load.

2. Doherty’s Threshold

The faster the system responds, the easier it is to keep the user’s attention.
A system is always outside the danger of slowing down, so long as its feedback happens within 0.4 seconds.
Up until 1982, the acceptable user response time was about two seconds. Experts then believed that this was the time frame when the user thinks about the task at hand. Later, two researchers from IBM — Walter Doherty and Arvind Tadani —found out that in two seconds a person is more likely to make a decision and switch their attention to something else.
Moreover, the faster the system responds, the faster the user responds. For example, if the system responds in 0.3 seconds, the person responds in 9 seconds. When the system’s response time drops to 3 seconds, so does user response time — by whole 16 seconds.

3. Fitts’s law

The closer and larger the elements are, the faster they are selected – this law comes thanks to psychologist Paul Fitts. He investigated the human motor system in 1954. He determined that the time to reach a goal depends on the distance and its size. That is, the farther and smaller the target, the higher the chances that hitting it will take time and will be difficult. This law is especially important when designing buttons in an interface. At the very least, buttons should be convenient and responsive, but ideally, they should also be easy to find.

4. Hick’s Law

The fewer the options, the faster the choice. The law was developed by psychologists William Hick and Ray Haimon in 1952. With many options, the right choice becomes a complicated matter. People spend more time time “thinking” and considering all the alternatives. If you cannot reduce the number of options for the user, break the process down into simpler steps.
Hick’s Law is used by many matching services. For example, a lot of the questions appear in turn, with no more than three available answers for each.

5. Jacob’s law

The more the site is similar to others, the sooner the user will like it.
Users spend a lot of time on various websites. Therefore, all competitors are expected to work on similar principles. The principle of similarity was deduced by the American UX specialist Jacob Nielsen. It comes down to this simple rule: do not burden the user with new things whenever you could use familiar patterns or practices.

6. The law of common space

Elements within the common border are perceived as a group.
This law is from Gestalt psychology. Scientists in this field have found that the associative nature of our brain always tends to combine objects into groups. Five principles relate to this process: proximity, similarity, continuity, isolation, and connectedness.
The easiest way to use the principle of grouping in your design is to frame the desired elements and find what features separate them from the rest. So, according to the law of common space, Facebook delimits posts.

7. The law of pregnancies

A complex image is interpreted in the simplest possible form.
In 1910, Gestalt psychologist Max Wertheimer noticed that we perceive a flickering series of lights as a continuously running line. This is because the brain tries not to overflow with unnecessary information and simplifies the complexity. This phenomenon was called pregnancies (German for “good, full form”).
When juxtaposed with design concepts, the law suggests that overly complicated images and interfaces create a puzzle for the user who simplifies it to something that fits their purpose. It is better to create something that needs no interpretation and stays that way for a long time. One good example of simple and reusable components is basic icons that depict common ideas or objects. These icons have the accepted recognition of street signs – everyone knows what they mean and they are hard to misinterpret.

8. The law of proximity

People perceive elements that are close to each other as a group.
This law is a logical continuation of another law: the law of common space. If you don’t want to outline the elements, just place them side by side. Or combine both laws: place all similar elements within the same border, group the subcategories. The principle is good at helping to determine the relationship of objects at a glance.
Any interface is built according to the law of proximity. For example, different backgrounds make it easy to highlight various blocks on a web page.

9. The Law of Similarity

Elements of the same shape are perceived as a group, even if separated.
We continue to move with gestalt. According to the law of similarity, if objects are similar in shape, the brain perceives them as interconnected. This technique works better for highlighting navigation elements than text boxes.
A striking example is Instagram. In the line of actual stories, the icons are in the same style - round and with inscriptions in the same format.

10. The law of connectivity

The more the similarity between elements, the more they are perceived as connected.
The law of connectivity interprets another principle by which elements are combined: visually similar components are perceived as a group. Use this to link similar functions. Give the elements one color, add the same lines, frames, and other shapes.
This principle works great for online stores, movie viewing services, and other resources, where there is a lot of information.

11. Miller’s Law

The user memorizes 7 (+ −2) items at a time.
In 1956, American psychologist George Miller found that the human brain remembers on average 7 (+ -2) objects. Therefore, groups in the interface should have a maximum of 9 elements. having fewer items (for example, five) is a better choice if you want to make sure no one gets lost in the navigation.
Long lists will tire you, even they are part of a useful menu. Break down the categories if necessary. For example, on the home page of Airbnb, the user’s top menu is small, and the search options are part of a separate category below it.

12. Postel’s Law

Be loyal to users and critical of yourself.
Any digital product must meet all user requirements, and the expert web designer‘s task is to foresee and implement them. A person should be able to perform as many actions within the product as he wants.
Think over transitions, arrange hints - do everything for better convenience, even if the process proves difficult and long.
The law was formulated by John Postel - one of the first engineers in the Internet field - primarily for computer networks and protocols. In design, it is easy to follow its law even in the smallest detail. For example, you can return to the home page from any YouTube page through the menu.

13. Occam’s Razor

From the same hypotheses, choose the one with fewer assumptions.
Occam’s Razor is an approach named after the English philosopher William of Ockham. The point is to add only what is needed to the system and exclude all that is unnecessary.
When the design is ready, analyze all the elements and remove the ones that you can do without. For example, assign the functions of several buttons to one drop-down list.
Occam’s razor principle is often used when upgrading and refining interfaces.

14. Pareto principle

20% of actions provide 80% of the result.
The 80/20 Principle was developed by the Italian economist Vilfredo Pareto. He noted that 80% of the land is owned by 20% of the population. This simple ratio formed a whole way of thinking. Several variations of this law work in UX:

  • 80% of users’ attention goes towards 20% of the interface
  • 20% of functions are responsible for 80% of actions

15. The Peak Rule

Users focus on the highlight and the end.
In 1993, a team of memory researchers conducted a series of experiments with immersion in cold water and found that people evaluate experience by what happens at the point of the most vivid experience, and also towards the end of the process.
A great example of implementation of this rule is a nice animation that appears when you finish a task on the Asana Task Scheduler website, providing a smooth visual confirmation denominating a completed action.


As you can see, a design without a real expert involved is doomed to failure. Even behind the simplest-looking design, there are thoughtful steps taken by someone who uses psychological principles to influence users.
Knowledge of psychology comes as a strong ally when we attempt to evaluate the user experience we created using design elements, layouts, and interfaces. It helps us understand the intent and motivation behind every action our clients make while browsing our web platforms. Factors like user response time or shopping journey patterns will become instrumental in improving the way clients perceive and interact with products and services.
We hope that the selected psychological principles and laws will help you deepen your knowledge and skills as a designer. Holding these principles handy when working on a design or interface, you will recognize their value and meaning. The more accurate the user profile, the better and the more convenient the delivery.

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Mariya Videva | UX Strategist  | UI/UX Designer

Mariya is an experienced User Interface (UI) and User Experience (UX) expert, with a strong tendency toward improving Customer Experience (CX). After a successful brainstorming session, she implements the user experiences used by millions of users thereafter.
There is no problem big enough for her not to tackle a solution to sometimes sophisticated user flows. User Experience Strategy sits at the heart of her actions, making her think ahead of time and beyond implementation.