Gutenberg
Laws of UX: A Guide to the Principles of User Experience Design
As individuals, our perception and processing of the world are shaped by an inherent cognitive framework. The field of psychology serves as a valuable tool to unravel this blueprint, providing insights into the workings of our minds. Designers can leverage this understanding to create intuitive and human-centred products and experiences.
By incorporating fundamental principles from psychology into their design approach, designers can craft products that align with users' natural tendencies and behaviours, rather than imposing a design on them. This user-centric design approach allows for the creation of products that seamlessly adapt to individuals, enhancing usability and user satisfaction. By employing psychology as a compass, designers can develop designs that resonate with users at a deeper cognitive and emotional level, resulting in products that are better tailored to their needs and preferences.
By leveraging the insights from psychology, designers can create products and experiences that cater to the cognitive and emotional aspects of human behaviour. This approach ensures that the design is aligned with users' inherent cognitive framework, making the product more intuitive, enjoyable and user-friendly. Ultimately, incorporating psychology into the design process empowers designers to build human-centred products that adapt to users, enhancing the overall usability and user satisfaction of the product or experience.
“Laws of UX” by Jon Yablonski highlights the importance of understanding psychology in UX design. It explores how key principles in psychology can be applied to create intuitive and human-centred digital interfaces. Topics covered include aesthetics, psychology principles, UX heuristics, predictive models, ethical considerations and a framework for application. This guide is a valuable resource for designers looking to enhance their understanding of how psychology impacts user behaviour and improve their design approach accordingly. Here we review the 10 laws of UX covered in the book.
Jakob’s Law
Users' familiarity with other websites means they prefer your site to have similar functionality. Expectations built around one familiar product can transfer to other similar products. Leveraging existing mental models allows for superior user experiences, where users can focus on their tasks rather than learning new models. When making changes, minimising discord by allowing users to continue using a familiar version for a limited time is crucial.
Jakob's Law, named after Jakob Nielsen, a User Advocate and principal of the Nielsen Norman Group co-founded with Dr. Donald Norman (former VP of Research at Apple Computer), is associated with the 'discount usability engineering' movement. This movement focuses on fast and cost-effective improvements of user interfaces and has resulted in the invention of several usability methods, including heuristic evaluation, by Dr. Nielsen.
Fitts’s Law
The time it takes to acquire a target depends on its distance and size. Touch targets in user interfaces should be large enough for accurate selection, with adequate spacing between them and strategically placed in accessible areas to ensure ease of use.
In 1954, psychologist Paul Fitts conducted a study on the human motor system and formulated Fitts' law, which states that the time required to move to a target depends on its distance and is inversely related to its size. This law explains the trade-off between speed and accuracy, where fast movements and small targets result in higher error rates. Fitts' law has been widely applied in design, influencing the size of interactive buttons, especially on finger-operated mobile devices, where larger buttons are preferred to minimise errors and improve usability. Additionally, Fitts' law emphasises the importance of minimising the distance between the user's task/attention area and task-related buttons to enhance efficiency in user interactions.
Hick’s Law
The time required for decision-making is influenced by the number and complexity of choices. To reduce decision time in situations where response times are critical, it's important to minimise choices. Breaking complex tasks into smaller steps can also help decrease cognitive load on users. To avoid overwhelming users, recommended options should be highlighted. Progressive onboarding can be used to minimise cognitive load for new users. However, it's important to strike a balance and avoid oversimplifying to the point of abstraction, as it may compromise the overall user experience.
Hick's Law, also known as the Hick-Hyman Law, was formulated by psychologists William Edmund Hick and Ray Hyman. Their research in 1952 aimed to understand how the number of stimuli impacted an individual's reaction time to a stimulus. The findings showed that when users are presented with more stimuli to choose from, it takes longer for them to make a decision on which one to interact with. This is because users need to interpret and decide among multiple choices, which can result in additional cognitive workload that users may find undesirable.
Miller’s Law
The capacity of the average person's working memory is limited to around seven (plus or minus two) items. However, it's important not to use this "magical number seven" as a justification for unnecessary design limitations. Instead, content should be organised into smaller, manageable chunks to aid users in processing, understanding and memorising information easily. It's worth noting that short-term memory capacity can vary among individuals, depending on factors such as prior knowledge and situational context.
George Miller proposed in 1956 that the span of immediate memory and absolute judgement is limited to around seven pieces of information. He defined the bit as the main unit of information, representing the amount of data required to choose between two equally likely alternatives. For instance, 4 bits of information would be needed to decide among 16 binary alternatives through four successive binary decisions. The channel capacity, or the point at which confusion leads to incorrect judgement, is determined by the quantity of bits that can be reliably transmitted through a channel within a given time frame.
Postel’s Law
Adopt a liberal approach when accepting user input, while being conservative in what you send in return. Show empathy, flexibility and tolerance towards the diverse actions and inputs that users may provide. Anticipate a wide range of input types, access methods and capabilities, while ensuring a reliable and accessible interface. Design with the ability to anticipate and plan for various scenarios, making the design more resilient. Accept variable input from users and adapt it to meet the requirements of your system or interface.
Postel's Law, also known as the Robustness Principle, was coined by Jon Postel, a notable early contributor to the development of the internet. The Law serves as a design guideline for software, particularly in the context of Transmission Control Protocol and networks and advocates for a conservative approach in what you do, but a liberal approach in what you accept from others. This means that while programs that send messages should conform strictly to specifications, programs that receive messages should be flexible and accept non-conformant input as long as the intended meaning is clear.
Peak–End Rule
The way people evaluate an experience is largely influenced by how they felt at its peak and at its end, rather than the overall sum or average of every moment within the experience. Therefore, it is crucial to carefully consider the most intense points and the final moments (the 'end') of the user journey in your design. Identifying the moments when your product is most helpful, valuable, or entertaining and designing to delight the end user can greatly impact their perception of the experience.
A groundbreaking study conducted in 1993 by Kahneman, Fredrickson, Charles Schreiber and Donald Redelmeier titled "When More Pain Is Preferred to Less: Adding a Better End" provided evidence for the peak-end rule. Participants were exposed to two versions of an unpleasant experience. In the first trial, they submerged a hand in 14°C water for 60 seconds. In the second trial, they submerged the other hand in 14°C water for 60 seconds, but then kept it submerged for an additional 30 seconds, during which the temperature was raised to 15°C. Afterward, participants were given the option to repeat one of the trials. Contrary to the law of temporal monotonicity, which suggests that longer exposure to discomfort would be less preferred, participants were more willing to repeat the second trial with the prolonged exposure to uncomfortable temperatures. Kahneman concluded that participants chose the longer trial based on their memory of it, as they liked it better or disliked it less, highlighting the significance of the peak and end moments in shaping overall experience perception.
Aesthetic–Usability Effect
The perception of aesthetics in design can significantly impact usability. Users often associate aesthetically pleasing design with higher usability. When a design is visually appealing, it triggers a positive response in the brain, leading users to believe that the design is more effective compared to equally usable designs that may be less visually appealing. In fact, users tend to be more forgiving of minor usability issues when the design is aesthetically pleasing. This can sometimes mask underlying usability problems, preventing them from being identified during usability testing, highlighting the influence of aesthetics on user perception of usability.
In 1995, researchers Masaaki Kurosu and Kaori Kashimura from the Hitachi Design Center conducted a study on the aesthetic-usability effect within the field of human-computer interaction. They tested 26 different variations of an ATM user interface (UI) and asked 252 participants to rate each design for both ease of use and aesthetic appeal. The study revealed a stronger correlation between participants' ratings of aesthetic appeal and perceived ease of use, compared to the correlation between aesthetic appeal and actual ease of use. Kurosu and Kashimura concluded that users are significantly influenced by the aesthetics of an interface, even when evaluating the underlying functionality of the system.
Von Restorff Effect
In situations where multiple similar objects are present, the one that stands out from the rest is more likely to be remembered. To enhance usability, it's important to make important information or key actions visually distinctive. However, it's crucial to exercise restraint in placing emphasis on visual elements to prevent competition among them and to avoid salient items from being mistaken as ads. Additionally, it's essential to ensure that important information is not solely reliant on colour, as this may exclude users with colour vision deficiency or low vision. Careful consideration should also be given to users with motion sensitivity when using motion to communicate contrast.
The theory, known as the von Restorff effect, was introduced by Hedwig von Restorff, a German psychiatrist and paediatrician, in her 1933 study. She observed that when participants were presented with a list of items that were categorically similar, but one item was distinctive and isolated from the rest, the memory for that particular item was significantly improved.
Tesler’s Law
In any system, there is an inherent level of complexity that cannot be eliminated. All processes possess a fundamental complexity that cannot be completely designed away and it must be assumed either by the system or the user. To enhance user experience, it is important to address as much of this complexity as possible during the design and development phases, with the aim of reducing the burden on users. However, caution should be exercised to avoid oversimplifying interfaces to the extent that essential functionality is abstracted or lost in the process.
While employed at Xerox PARC in the 1980s, Larry Tesler recognized that the way users interact with an application is just as crucial as the application itself. In Dan Saffer's book, Designing for Interaction, an interview with Larry Tesler discusses the law of conservation of complexity. Tesler argues that, in most cases, engineers should invest an additional week in reducing the complexity of an application, rather than burdening millions of users with an extra minute of usage due to the added complexity. However, Bruce Tognazzini suggests that people tend to resist reductions in the complexity of their lives. Consequently, when an application is simplified, users may attempt more complex tasks.
Doherty Threshold
Productivity greatly improves when a computer and its users interact at a pace of less than 400ms, ensuring that neither party has to wait on the other. To keep users engaged and boost productivity, provide system feedback within this timeframe. Utilise techniques such as perceived performance to enhance response time and minimise the perception of waiting. Visual elements such as animation or progress bars can be employed to engage users while loading or processing occurs in the background. Interestingly, intentionally adding a delay to a process can increase its perceived value and foster trust, even if the process itself is actually shorter in duration.
In 1982, a research paper by Walter J. Doherty and Ahrvind J. Thadani established the requirement for computer response time to be 400 ms, as opposed to the previous standard of 2,000 ms (2 seconds). If a human's command could be executed and returned with an answer within 400 ms, it was considered to exceed the Doherty threshold.