7 psychological laws underlying UI/UX design and how to implement them in your product
The Zeigarnik Effect
Have you ever opened a music player app and unexpectedly found that the last unfinished song is the one that's been playing in your head all day?
This is exactly how the Zeigarnik effect works. It states that the human brain remembers material related to an unfinished task better than a completed one. In the 1920s, researcher Bluma Zeigarnik noticed this while observing waiters: they remembered details of unpaid orders well and paid orders poorly.
The power of incompleteness explains our addiction to TV series. Scriptwriters end each episode with a cliffhanger to create that sense of incompleteness that makes us remember to come back to the screen the next day.
Okay, but how does this work in a digital product? Designers add elements like progress indicators that show a task is incomplete, motivating the user to make a final effort and complete it.
Cognitive Load
Computers have RAM, and the human brain has cognitive load, also called working memory. This term was coined in the 1980s by John Sweller. He noticed that overloading working memory slows down the learning process and reduces the number of completed tasks.
When it comes to UX design, the cognitive load law states: "Don't place too much information on one screen if you want users to pay attention to it."
Working for many years with complex products containing large amounts of data, we compiled a list of the best UX patterns that help reduce cognitive load:
- Wizard pattern
- Two-level menus
- Universal filtering systems
In UX design, the optimal cognitive load is set at 5±2 items. It is also known as
Miller's Law
The magic number seven, plus or minus two, was introduced by George A. Miller in 1956. Decades later, it became a golden rule of UX design. It is not recommended to have more items in menus, checkbox series, etc.
Social Proof
Let's tell you about an interesting experiment conducted back in 2006, when MySpace was the most popular social network. A small music site was created with songs from unknown bands. One group of users could see the download count for each song, while the other group could not. Additionally, those who saw the download counts were divided into eight "worlds," each with its own download counter.
The result? The most popular songs in different groups were different. People listened more to those that were already "popular." This doesn't turn the world upside down: the best songs were still downloaded, and the worst were not. However, for most "average" songs, the download count greatly influenced their ranking.
Users tend to act like others. That's why apps inform you about other users whenever possible. For example, Duolingo shows between exercises how many people are learning the same language as you. Duolingo is a true hacker of human psychology: if you want to learn more such tricks, just open the app (and try not to get addicted).
Scarcity
People value things more when there are fewer of them.
Remember the panic over toilet paper during the first days of the 2020 lockdown. Scarcity can make people act irrationally. But what does this mean in UX? When an app wants to encourage a user to do something, it shows that opportunities are limited. This increases the likelihood that users will take advantage of that opportunity.
Too Good To Go, a food-saving app, always shows how many offers are left at each location.
In this case, the trick aligns with the app's goal: saving food from waste. Unfortunately, some other products use it only to create an unjustified sense of scarcity and boost sales.
Labor Illusion
People value things more when they feel more labor/time has been invested in them (and we aren't talking about the times when you had to go to government offices and wait weeks for a document to be ready).
The most famous example is the booking service Kayak (it's considered the first to use the labor effect in UX design). Now it can be seen in almost any flight booking service.
When you click the "Search" button, you don't get all results immediately. Instead, a "waiting" message appears with something like "we are checking 264 sites for the best deals." Thus, people value the obtained information even more (because even a digital algorithm cares about your trip and does its best!)
This technique is often used both in cases where loading time needs justification (it's not about a slow connection, but about how hard we are working for you!), and in cases where waiting time is artificially increased by a few seconds.
Weber's Law
Users adapt better to small gradual changes
Aversion to change is ingrained in human nature. We like our habits and routines, and most people are not thrilled about changes they didn't ask for. This is a common issue when we talk about redesigning digital products. Users feel irritated and start criticizing it immediately simply because they are not used to it.
That's why smart companies make gradual changes. The "Urban Sports" club started with an incredibly profitable offer: 30 visits to any sports venue in any city for just 5900 rubles.
It was quite obvious that such a model could not be sustainable and profitable for the company and sports clubs. So when at some point the number of visits was reduced to 15, it was expected but still upset some users. A few months later, Urban Sports made another pricing change: now only 10 visits per month were allowed for 6600 rubles. Of course, people were still disappointed, but gradual changes helped reduce user churn compared to abrupt large changes.
Such was the case with Spoonfed. They were in the process of major changes, including a migration to a new platform, and therefore needed a redesign. Such a large project takes a lot of time—up to a year.
The product interface required many changes, so to improve the user experience faster and acclimate users to the new look, our designer prepared an intermediate version of the design. Its implementation didn't take long and included new navigation (left side instead of top panel) and an updated visual style.
Conclusion
Honestly, basic knowledge of psychology will benefit most professionals, not just designers. The laws described in this article are just an arbitrary selection from hundreds of rules people have created to describe our complex and often irrational behavior.