An assembled collection
of design methods cards
for easy reference

Psychological
Principals

As humans, we have an underlying “blueprint” for how we perceive and process the world around us, and the study of psychology helps us decipher this blueprint. Designers can use this knowledge to build more intuitive, human centered products and experiences. Instead of forcing users to adapt to the design of a product or experience, we can use some key principles from psychology as a guide for designing in a way that is adapted to people.

Download the Laws of UX

Jakob’s Law

Users spend most of their time on other sites, and they prefer your site to work the same way as all the other sites they already know.

Fitts's Law

The time to acquire a target is a function of the distance to and size of the target.

Hick's Law

The time it takes to make a decision increases with the number and complexity of choices available.

Miller’s Law

The average person can keep only 7 (± 2) items in their working memory.

Postel’s Law

Be conservative in what you do, be liberal in what you accept from others.

Peak–End Rule

People judge an experience largely based on how they felt at its peak and at its end, rather than on the total sum or average of every moment of the experience.

Aesthetic–Usability Effect

Users often perceive aesthetically pleasing design as design that’s more usable.

Von Restorff Effect

When multiple similar objects are present, the one that differs from the rest is most likely to be remembered.

Tesler’s Law

Tesler’s law, also known as the law of conservation of complexity, states that for any system there is a certain amount of complexity that cannot be reduced.

Doherty Threshold

Productivity soars when a computer and its users interact at a pace(<400 ms) that ensures that neither has to wait on the other.

Methods

Cognitive walkthrough

An evaluation method in which people work through a set of representative tasks and ask questions about the task as they go.

Contextual inquiry

The product team unobtrusively observes participants at work, with their permission, then asks questions.

Dot voting

A simple voting exercise to identify a group’s collective priorities.

Five whys

An iterative process for identifying the root cause of a problem by posing the question “Why?” at least five times to help separate symptoms from causes.

KJ method

A facilitated exercise in which participants list their individual priorities onto cards, collect them as a group, organize them by relationship, and establish group priorities through individual voting.

Peak–End Rule

People judge an experience largely based on how they felt at its peak and at its end, rather than on the total sum or average of every moment of the experience.

Aesthetic–Usability Effect

Users often perceive aesthetically pleasing design as design that’s more usable.

Von Restorff Effect

When multiple similar objects are present, the one that differs from the rest is most likely to be remembered.

Tesler’s Law

Tesler’s law, also known as the law of conservation of complexity, states that for any system there is a certain amount of complexity that cannot be reduced.

Doherty Threshold

Productivity soars when a computer and its users interact at a pace(<400 ms) that ensures that neither has to wait on the other.

Jakob’s Law

Users spend most of their time on other sites, and they prefer your site to work the same way as all the other sites they already know.

Key Takeaways

Users will transfer expectations they have built around one familiar product to another that appears similar.
By leveraging existing mental models, we can create superior user experiences in which the users can focus on their tasks rather than on learning new models.
When making changes, minimize discord by empowering users to continue using a familiar version for a limited time.

Overview

There is something incredibly valuable to be found in familiarity. Familiarity helps the people interacting with a digital product or service know immediately how to use it, from interacting with the navigation to finding the content they need to processing the layout and visual cues on the page in order to understand the choices available to them. The cumulative effect of mental effort saved ensures a lower cognitive load. In other words, the less mental energy users have to spend learning an interface, the more they can dedicate to achieving their objectives. The easier we make it for people to achieve their goals, the more likely they are to do so successfully.

As designers, it is our objective to ensure people successfully achieve their goals when using the interfaces we’ve built by eliminating as much friction as possible. Not all friction is bad—in fact, sometimes it is even necessary. But when there is an opportunity to remove or avoid extraneous friction, or friction that doesn’t provide value or service a purpose, then we should do so. One of the primary ways designers can remove friction is by leveraging common design patterns and conventions in strategic areas such as page structure, workflows, navigation, and placement of expected elements such as search.

When we do this, we ensure people can immediately be productive instead of first having to learn how a website or app works. In this chapter, we’ll take a look at some examples of how this design principle can be achieved—but first, let’s look at its origins.

Origins

Jakob’s law (also known as “Jakob’s law of the internet user experience”) was put forth in 2000 by usability expert Jakob Nielsen, who described the tendency for users to develop an expectation of design conventions based on their cumulative experience from other websites. This observation, which Nielsen describes as a law of human nature, encourages designers to follow common design conventions, enabling users to focus more on the site’s content, message, or product.

In contrast, uncommon conventions can lead to people becoming frustrated, confused, and more likely to abandon their tasks and leave because the interface does not match up with their understanding of how things should work.The cumulative experience that Nielsen refers to is helpful for people when visiting a new website or using a new product because it informs their understanding of how things work and what’s possible.

This underlying factor is perhaps one of the most important in user experience, and it is directly related to a psychological concept known as mental models.

+

Fitts’s Law

The time to acquire a target is a function of the distance to, and size of the target.

Key Takeaways

Touch targets should be large enough for users to accurately select them.
Touch targets should have ample spacing between them.
Touch targets should be placed in areas of an interface that allow them to be easily acquired.

Overview

Usability is a key aspect of good design. It implies ease of use, which means the inter face should be easy for users to understand and navigate. Interaction should be painless and straightforward, requiring minimal effort. The time it takes for users to move to and engage with an interactive object is a critical metric. It’s important that designers size and position interactive objects appropriately to ensure they are easily selectable and meet user

expectations with regard to the selectable region—a challenge compounded by the differing precision of the range of input methods available today: mouse, finger, etc.

To aid in this endeavor we can apply Fitts’s law, which states that the time it takes for a user to engage with an object is relative to its size and the distance to it. In other words, as the size of

an object increases, the time to select it goes down. Additionally, the time to select an object decreases as the distance that a user must move to select it decreases. The opposite is true as well: the smaller and further away an object is, the more time it takes to accurately select it. This rather obvious concept has far-reaching implications.

Origins

The origins of Fitts’s law can be traced back to 1954, when American psychologistPaul Fitts predicted that the time required to rapidly move to a target area is a function of the ratio between the distance to the target and the width of the target(Figure 2-1). Today, it’s regarded as one of the most successful and influential mathematical models of human motion, and it’s widely used in ergonomics and human–computer interaction to model the act of pointing, either physically or virtually.