Design decisions are often based on who our users are, their mental models, their goals, their motivations and their problems. Learning about the psychological principle that governs human behavior and the way they act, anticipate, achieve their goals are tantamount to a smooth user experience that helps improve better adoptions of new products, lifts engagement and improves retention of products.

These are fundamental metrics that drive a digital product’s success. Most often the most self-aware of the users are also unaware of the guiding forces that shape and affect the way they interact with products. 

So, without further ado, let’s jump right into some of the most prominent psychological principles that we come across daily, but hardly remain aware of the guiding force within them. 

Zeigarnik Effect 

Ever notice a song continuously playing on your mind involuntarily? Some call it earworms. But do you know it is governed by the Zeigarnik effect, a psychological effect named after a renowned psychologist Bluma Zeigarnik?

The Zeigarnik effect occurs when a task is incomplete or interrupted before it is completed and is more readily recalled than the finished tasks. Unconsciously, our mind worries about a task that hasn’t finished.

So, there's an element of task stickiness to our brain which compels us to finish the task. Soaps and operas do employ this effect: for example, an episode might be finished but the story is unfinished. Cliffhangers on Netflix leave their viewers eager to learn more and thus creating greater recall and curiosity when they come back to watch it again. 

Zeigarnik Effect in Actions:

  • Designers have used this effect over time in product designing. Video games or gamification apps led by streaks and variable rewards deploy Zeigarnik to the core. The in-app purchases that pop up in the middle of the game drives more purchases as gamers want to finish the game they started or reach to the next level of the game. Gamers are left to view how many more levels are left to be completed.

lans game ui

  • In our daily usage of apps, a progress indicator or a step indicator is a typical example of this effect coming into play. It’s meant to compel users to do certain tasks they wouldn't otherwise do because it provides incentive to free up from the stickiness of unfinished tasks in our brain.

daily ui progress bar

  • Next time when you come across an incomplete profile stating 70% completed, rest assured that Zeigarnik effect is on the play.

profile progress

Related Article: The Psychology Behind Custom Product Purchases

Hick’s Law

Hick Law states that the more choices you give to the user the longer the decision time to make a choice. This is particularly useful when while using a product, we first tend to find the functionalities that might answer our needs and more specifically the functionalities we need the most. If at any point in time we get overwhelmed, confused and frustrated with the choices we have to make to achieve his goal, it’s a natural tendency for us to leave the product quickly. 

Most often products are crammed with functionalities that might be useful for the user but given the time taken to retrieve those functionalities makes it an arduous task for users to take a call quickly. 

Named after a team of British and American psychologists William Edmund Hick and Ray Hyman, Hick’s Law came into existence in 1952. It explores the relationship between the number of stimuli given and a user’s response time to any given stimuli. Simply put, if users are given too many choices, it takes time for them to interpret and decide which adds extra load on the users.

Hick’s law in Actions:

Onboarding steps broken into chunks so as to not overwhelm users respecting the time and effort required to make a choice.

Onboarding Steps: (UI Movement)

ui movement

Drop down items are reduced to make it easy to make a decision between less numbers of items to rate the service vs. 10 items from which to choose.

don't do

Pricing Table Recommendation makes it easy for the users to focus on one set of offerings rather than go through each of the three.

right business plan

Menu Item Ordered 

Menu items are nicely chunked and categories so as to increase discoverability effortlessly and thereby reducing decision time.

header navigation menu

Serial Positioning Effects

This states the tendency of a person to be better able to remember the first item and the last item in a list. The underlying principles behind this effect are the Primacy and the Recency effect. The primacy effect is a cognitive bias that enables users to remember primary information better than the information presented later on. The recency effect on the other hand is a cognitive bias that enables people to remember ideas, thoughts, items that came last or more recently when going through a list.

Coined by Hermann Ebbinghaus, the serial position effects can hugely impact the user experience of a product. 

Serial Positioning Effect in Action

List Item First and Last, i.e Home and Contact info., are the two most important elements in the list, and they have been placed in the first and the last place in the list strategically to increase recall.

Learning Opportunities


Related Article: CX Decoded Podcast: Are Customers Truly Connected to Your Brand?

Jakob’s Law

This law states that users spend most of the time on popular sites they use on a day to day basis. That way the user wants the new site to pretty much work the same way as they are accustomed. 

Coined by Dr. Jakob Nielsen, who is founding partner of Nielsen Group along with Don Norman, this law can be applied to almost every product unless it’s very disruptive. 

This can play a critical part in knowing users' existing mental models and experiences during product or UX research and deploying the same mental modals and experiences in the new product. By leveraging existing mental models, the experience derived from using familiar products can be transferred to the existing product without creating new mental models. This saves a lot of time in building functionalities that are akin to users rather than spending time and effort building new mental models and making your users familiar with it. As a result the product might face low user adoption.

Jakob law in Action 

Same experience with a long Search button and Navigation menu on top mimicking Amazon’s experience which is popular among users across the world.

alibaba amazon

Von Rostor Effect

It’s a simple effect that states the odd one from the rest of the similar looking items is going to be remembered the most. Though it sounds common sense but in the product's UX field its existence is mostly felt. 

Von Rostor Effect in Action

CTA button have highest contrast amid all the other composition in the screen to draw attention and increase chances of user taking the action.

plants marketplace

Pricing Table Recommendation highlighted using contrast and color treatment to make it standout from rest of the four cards. 

right business plan pricing

Aesthetic Usability Test

This test goes by the looks and the beauty of the product. It states that the more attractive and pleasing interfaces are going to be perceived as more usable. It’s a bias that makes us feel something that looks better will work better even if that’s not exactly the case.

People are ready to endure minor usability issues if the interface is visually appealing. 

However, in some usability testing, it has been observed that it can mask UI problems and thus prevents any issues with the UI. 

Beautiful app interface with nice imagery, composition, structure, typography, spacing to lure users to use the app. 

game application ui design

While there are tons of psychological principles at work, I have tried to combine the most basic ones that we come across every day. Stay tuned for more coverage on this topic in future articles.