The Power of Psychology in UX Design: Creating User-Centered Interfaces

Karl Reitzig
4 min readMar 14, 2023
Photo by Bret Kavanaugh on Unsplash

As UX designers, our primary aim is to design user-centred systems that make it easy for humans to use. This means it’s essential to understand how people think and behave to ensure our designs take their cognitive and physical constraints into account.

In this blog post, we’ll delve into 7 fundamental psychological principles utilized in UX design.

These principles serve as an objective and empirical basis for shaping and evaluating our designs with concepts that experts before us have studied in a lot of depth. They also enable us to articulate and motivate our recommendations more effectively with our team and stakeholders through a shared vocabulary and academic validity.

Activity Theory

The first principle we’ll explore is activity theory, which serves as the foundational theory for UX design, with many sub-theories like situated action theory and distributed cognition building off its principles. Activity theory explains how we as humans are not separate from the world around us, but that our physical, social, and cultural environments play an active part in shaping our behaviour and thinking.

This means that to understand our users, we should first get a clear understanding of their context and environments. It also means that we need to carefully consider how the user’s environment will affect the system (e.g., the buttons or information architecture) and how the system will influence the environment as well.

See the seminal work on Activity theory by Bonnie Nardi.

Cognitive Load

This principle explains how we have a limited amount of working memory to use at a time. It’s similar to the RAM of a computer or the limited amount of bandwidth that a single Wi-Fi router can provide.

As UX designers, it’s essential to understand what the user’s cognitive load is during a task and avoid overloading it to ensure that they can accomplish a task with limited stress and errors.

Think about a GPS system. It’s usually used in highly stressful environments and in combination with other actions and sources of information like road signs and screaming children, which all take up working memory. To avoid high cognitive loads, we need to ensure that the GPS interface is not mentally demanding and complex, through techniques like distributed cognition.

Distributed Cognition

Building on Activity Theory, we have Distributed Cognition, which articulates how our memory can be distributed between objects in the world around us to reduce our cognitive load by removing the need to store every piece of information in our working memory.

For example, think about a checkout flow for an e-commerce store. A good user interface will have a section in the journey dedicated to showing the user what they have in their cart, along with details like the price, to free their minds to concentrate on other things more easily.

Hick’s Law

Hick’s Law is based on the principle that ‘more is not always better’ and motivates us to pursue simplicity. It describes how the time it takes for people to make a decision significantly increases as we add more choices, leading to analysis paralysis.

For example, when choosing a payment plan for an online subscription, two or three options might be easy to compare. However, if there are too many options, it can negatively affect the user and increase the risk of abandonment.

Aesthetic-usability effect

Ever wondered if it matters what a website, product packaging, or book covers really look like? This psychological phenomenon explains that humans often associate things that look good with quality and thoughtful design.

This means that people will perceive something as more usable and effective than it actually is if it looks good. But note that this is only true to a certain extent and when the usability issues reach a certain point it stops being relevant.

Halo effect

This is another human bias that explains how first impressions matter. If users had a positive experience with their first touch point of a system, they will often carry those positive sentiments through towards the other interactions of the system after that.

This effect creates a solid case for the significance of a well-crafted home page and making sure that any early touch points are carefully planned out.

Direct manipulation

Direct manipulation is a design concept that was introduced with the advent of graphical user interfaces (GUIs). Its main objective is to create a computer system that mimics real-world objects and actions in order to improve the usability and efficiency of a user’s interaction on a screen.

By leveraging a user’s existing mental model of real-world objects like trash cans and folders, users can directly manipulate graphical objects on the screen through actions like clicking and dragging items with minimal effort and steps. This approach can reduce the cognitive load required to complete tasks on a computer system and improve usability by providing immediate feedback.

Some honourable mentions to delve into further include: Social proof, mental models, the physiological effects of stress, and various cognitive biases.

It is important that we study theories and psychological principles like the ones we discussed above, alongside many others, to ensure that our designs are more user-centric by keeping the needs and constraints of the humans using our systems in mind through frameworks based on empirical evidence.

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Karl Reitzig

I’m a South African UX designer sharing my thoughts on digital design and tech.