Four psychology principles every UX designer should know

You don't need to be a psychologist to conduct user research, but understanding the field can help you make better design decisions.

Though the concept of human-centered design has gone by many names over the years (human factors, usability, human-computer interaction, user experience design), the philosophy and methodology largely took hold during World War II.

Because of military necessity and several other factors, U.S.-based psychologists rigorously studied the limits of the human brain and body to help inform the design of airplane cockpits. The idea was that human psychology could be used to design a cockpit to minimize human error.

Similar work has been done to reduce errors in other high-stakes professions. For example, an understanding of human psychology has been used to help surgeons reduce errors in their work.

Whether you're improving the experience for a pilot, surgeon, or website user, the principles of human psychology can help inform your work. These evidence-based, scientific principles can elevate your UX design practice.

1) Proximity-compatibility principle

The proximity-compatibility principle states that items related to a common task should be grouped together within a display or screen.

This design principle evolves from a basic Gestalt visual principle. The Gestalt philosophy suggests that humans perceive a whole “greater than the sum of its parts,” meaning our brains are heroes at making sense of complex visual input. According to the Gestalt principle of proximity, we perceive grouped objects as more related than objects spaced farther apart.

As a UX designer, go a little deeper and consider how the proximity of items influences not only how a display looks and feels, but also the user’s task flow.

For example, look at how Eventbrite uses white space to group information together in close proximity. The pricing information and ticket link are located together because those items are integral to the same task: buying a ticket. The event date, time, and calendar are placed together because it’s likely that while users are examining event details, they also want to access their personal calendars.

By grouping related, compatible information, you help the user naturally progress through your interface.

2) Continuity principle

The continuity principle suggests that we perceive elements as related or connected when elements are visually arranged on a line or curve. This perception can even override other strong visual grouping features like color.

The continuity principle matters in UX when arranging elements on a page. On Amazon, we perceive the rows of books to be related because they are arranged in a continuous line. The user understands that she is looking at an organized list of items curated by Amazon algorithms.

On the other hand, Pinterest-style blocks have variable heights. The arrangement of non-straight rows conveys a less cohesive arrangement of items. This design feels like more of a scattered corkboard than an orderly filing cabinet, which is perfect for viewing a user-curated assortment of sources and ideas.

Users probably perceive Pinterest lists as less interrelated than Amazon lists, even though they never consciously consider it. The two designs visually communicate different psychological meanings for different purposes.

In your own UX designs, think about using continuous or non-continuous lines to communicate relationships within information.

3) Focal point principle and visual hierarchy

Our visual attention is drawn to items that stand out from the rest of the environment. You can thank our expired cave person needs, like scavenging for food and avoiding predators, for that. You can use the focal point principle to your design advantage by guiding visual attention to the most important page elements.

Designers intuitively understand focal points very well. UX designers should also think about focal points as a way to make an experience easier and make pages super scan-able while avoiding overburdening the user’s brain.

Notice that the Blue Apron homepage contains “Sign Up” and “Sign Up Now” buttons that are orange and rectangular, in contrast to the blue logo, borderless navigation links, and white tag line.

Orange is effective here because the color and shape of the buttons visually contrast with the rest of the navigation. If a user wants to sign up for Blue Apron, he’ll have no trouble figuring out how, which also translates to sales benefits for the company. The two similar-looking orange buttons achieve the same goal, which is important for clarity’s sake.

As a UX Designer, consider how to employ focal points to guide users to accomplish their goals. Besides color and contrast, you can use size, shape, typography, or motion to guide visual attention.

Of course, limit your intended focal points to only the most important items, or users will feel overwhelmed.

And speaking of overwhelmed users, how do you organize large amounts of information to be easily digestible? Use a visual hierarchy. Humans naturally perceive the biggest or most attention-grabbing items to be most important, so you can use visual differentiators to create an organization of information, from highest order to lowest order.

Newspaper editorial designers are really good at creating a visual hierarchy. Historically, pre-Twitter, passers-by on the street needed to quickly scan front pages in a newsstand to decide whether to buy a paper. Readers can rapidly digest much information thanks to headlines or images providing a focal point and subheadings giving a visual hierarchy outlining the important stories.

4) Hick’s Law

This final psychology principle is actually classified as a ‘law’ because there’s a mathematical formula involved. In the 1950s, psychologist William Edmund Hick identified that the time it takes for a person to make a decision is dependent on how many options they are given.

What does this mean to UX professionals? To make things easier on the user, limit the number of options provided. On an app or website, if users face too many options without a clear path, their tendency may be to quit and move on.

If you’ve ever eaten at a Cheesecake Factory restaurant, you recall their massive menu. There are pages and pages of options, spanning several cuisine categories. And that’s not even including the cheesecake.

Luckily, by this point, customers have probably committed to sitting in a restaurant booth. And luckily for the business, the tasty, overindulgent calories keep them coming back for more.

You don't need to toss out all the information and features, but if you organize decisions in a way that makes sense, you can keep users on board. That means prioritizing and opting for simplicity whenever possible. Think clear categories, logical flow, nothing extraneous.

There is a very thorough article on Hick’s Law that was recently published on the Interaction Design Foundation website if you’d like to read more examples.

The psychology plays into UX design, from visual perception to social psychology and behavior. The more you understand how people think and feel, the better you can create positive, helpful, delightful experiences.