Laws of UX
Occam's Razor
OVERVIEW Among competing hypotheses that predict equally well, the one with the fewest assumptions should be selected. KEY TAKEAWAYS Analyze each element and remove as many as possible, without compromising the overall function. ORIGINS Occam's razor (also Ockham's razor; Latin: lex parsimoniae "law of parsimony") is a problem-solving principle that, when presented with competing hypothetical answers to a problem, one should select the one that makes the fewest assumptions. The idea is attributed to William of Ockham (c. 1287-1347), who was an English Franciscan friar, scholastic philosopher, and theologian.
Parkinson's Law
OVERVIEW Any task will inflate until all of the available time is spent. ORIGINS Articulated by Cyril Northcote Parkinson as part of the first sentence of a humorous essay published in The Economist in 1955 and since republished online, it was reprinted with other essays in the book Parkinson's Law: The Pursuit of Progress (London, John Murray, 1958). He derived the dictum from his extensive experience in the British Civil Service.
Postel's Law
OVERVIEW Be liberal in what you accept, and conservative in what you send. KEY TAKEAWAYS Be empathetic, flexible, and tolerant to any number of actions the user could possibly take. This means accepting variable input from users, translating input to meet the requirements, defining boundaries for input, and providing clear feedback to the user. ORIGINS Postel's Law (also known as the Robustness Principle) was formulated by Jon Postel, an early pioneer of the Internet. The Law is a design guideline for software, specifically in regards to TCP and networks.
Law of Common Region
OVERVIEW Elements tend to be perceived into groups if they are sharing an area with a clearly defined boundary. KEY TAKEAWAYS Adding a border around an element or group of elements is an easy way to create common region. Common region can be created by defining a background behind an element or group of elements. ORIGINS The principles of grouping (or Gestalt laws of grouping) are a set of principles in psychology, first proposed by Gestalt psychologists to account for the observation that humans naturally perceive objects as organized patterns and objects, a principle known as Prägnanz. Gestalt psychologists argued that these principles exist because the mind has an innate disposition to perceive patterns in the stimulus based on certain rules. These principles are organized into five categories: Proximity, Similarity, Continuity, Closure, and Connectedness.
Law of Uniform Connectedness
OVERVIEW Elements that are visually connected are perceived as more related than elements with no connection. KEY TAKEAWAYS Group functions of a similar nature so they are visually connected via colors, lines, frames, or other shapes. ORIGINS The principles of grouping (or Gestalt laws of grouping) are a set of principles in psychology, first proposed by Gestalt psychologists to account for the observation that humans naturally perceive objects as organized patterns and objects, a principle known as Prägnanz. Gestalt psychologists argued that these principles exist because the mind has an innate disposition to perceive patterns in the stimulus based on certain rules. These principles are organized into five categories: Proximity, Similarity, Continuity, Closure, and Connectedness.
Law of Proximity
OVERVIEW Objects that are near, or proximate to each other, tend to be grouped together. KEY TAKEAWAYS Proximity helps to establish a relationship with nearby objects. Proximity helps users understand and organize information faster and more efficiently. ORIGINS The principles of grouping (or Gestalt laws of grouping) are a set of principles in psychology, first proposed by Gestalt psychologists to account for the observation that humans naturally perceive objects as organized patterns and objects, a principle known as Prägnanz. Gestalt psychologists argued that these principles exist because the mind has an innate disposition to perceive patterns in the stimulus based on certain rules. These principles are organized into five categories: Proximity, Similarity, Continuity, Closure, and Connectedness.
Peak-End Rule
OVERVIEW People judge an experience largely based on how they felt at its peak and at its end, rather than the total sum or average of every moment of the experience. KEY TAKEAWAYS Pay close attention to the most intense points and the final moments (the "end") of the user journey. Identify the moments when your product is most helpful, valuable, or entertaining and design to make those moments even better. Remember that people recall negative experiences more vividly than positive ones. ORIGINS A 1993 study titled "When More Pain Is Preferred to Less: Adding a Better End" by Kahneman, Fredrickson, Charles Schreiber, and Donald Redelmeier provided groundbreaking evidence for the peak-end rule. Participants were subjected to two different versions of a single unpleasant experience. The first trial had subjects submerge a hand in 14°C water for 60 seconds. The second trial had subjects submerge the other hand in 14°C water for 60 seconds, but then keep their hand submerged for an additional 30 seconds, during which the temperature was raised to 15 °C. Subjects were then offered the option of which trial to repeat. Against the law of temporal monotonicity, subjects were more willing to repeat the second trial, despite a prolonged exposure to uncomfortable temperatures. Kahneman et al. concluded that "subjects chose the long trial simply because they liked the memory of it better than the alternative (or disliked it less)".
Zeigarnik Effect
OVERVIEW People remember uncompleted or interrupted tasks better than completed tasks. KEY TAKEAWAYS Use progress bars for complex tasks to visually indicate when a task is incomplete, and thus increase the likelihood it will be completed. ORIGINS Bluma Wulfovna Zeigarnik (1900 - 1988) was a Soviet psychologist and psychiatrist, a member of the Berlin School of experimental psychology and Vygotsky Circle. She discovered the Zeigarnik effect and contributed to the establishment of experimental psychopathology as a separate discipline in the Soviet Union in the post-World War II period. In the 1920s she conducted a study on memory, in which she compared memory in relation to incomplete and complete tasks. She had found that incomplete tasks are easier to remember than successful ones. This is now known as the Zeigarnik effect. She later began working at the Institute of Higher Nervous Activity which is where she would meet her next big influence Vygowski, and become a part of his circle of scientists. It was also there that Zeigarnik founded the Department of Psychology. During that time, Zeigarnik received the Lewin Memorial Award in 1983 for her psychological research.
Law of Prägnanz
OVERVIEW People will perceive and interpret ambiguous or complex images as the simplest form possible, because it is the interpretation that requires the least cognitive effort of us. KEY TAKEAWAYS The human eye likes to find simplicity and order in complex shapes because it prevents us from becoming overwhelmed with information. Research confirms that people are better able to visually process and remember simple figures than complex figures. ORIGINS In 1910, psychologist Max Wertheimer had an insight when he observed a series of lights flashing on and off at a railroad crossing. It was similar to how the lights encircling a movie theater marquee flash on and off. To the observer, it appears as if a single light moves around the marquee, traveling from bulb to bulb, when in reality it's a series of bulbs turning on and off and the lights don't move it all. This observation led to a set of descriptive principles about how we visually perceive objects. These principles sit at the heart of nearly everything we do graphically as designers.
Doherty Threshold
OVERVIEW Productivity soars when a computer and its users interact at a pace (<400ms) that ensures that neither has to wait on the other. KEY TAKEAWAYS Provide system feedback within 400ms in order to keep users' attention and increase productivity. Use perceived performance to increase response time and reduce the perception of waiting. ORIGINS In 1982 Walter J. Doherty and Ahrvind J. Thadani published, in the IBM Systems Journal, a research paper that set the requirement for computer response time to be 400 milliseconds, not 2,000 (2 seconds) which had been the previous standard. When a human being's command was executed and returned an answer In under 400 milliseconds, it was deemed to exceed the Doherty threshold, and use of such applications were deemed to be "addicting" to users.
Tesler's Law
OVERVIEW Tesler's Law, also known as The Law of Conservation of Complexity, states that for any system there is a certain amount of complexity which cannot be reduced. ORIGINS While working for Xerox PARC in the mid-1980s, Larry Tesler realized that the way users interact with applications was just as important as the application itself. The book Designing for Interaction by Dan Saffer, includes an interview with Larry Tesler that describes the law of conservation of complexity. The interview is popular among user experience and interaction designers. Larry Tesler argues that, in most cases, an engineer should spend an extra week reducing the complexity of an application versus making millions of users spend an extra minute using the program because of the extra complexity However, Bruce Tognazzini proposes that people resist reductions to the amount of complexity in their lives. Thus, when an application is simplified, users begin attempting more complex tasks.
Pareto Principle
OVERVIEW The Pareto principle states that, for many events, roughly 80% of the effects come from 20% of the causes. KEY TAKEAWAYS Focus the majority of effort on the areas that will bring the largest benefits to the most users. ORIGINS Its origins stem back to Vilfredo Pareto, an economist who noticed 80% of Italy's land was owned by 20% of the population. Though it might seem vague, the 80/20 way of thinking can provide insightful and endlessly applicable analysis of lopsided systems, including user experience strategy.
Von Restorff Effect
OVERVIEW The Von Restorff effect, also known as The Isolation Effect, predicts that when multiple similar objects are present, the one that differs from the rest is most likely to be remembered. KEY TAKEAWAYS Make important information or key actions visually distinctive. ORIGINS The theory was coined by German psychiatrist and pediatrician Hedwig von Restorff (1906-1962), who, in her 1933 study, found that when participants were presented with a list of categorically similar items with one distinctive, isolated item on the list, memory for the item was improved.
Miller's Law
OVERVIEW The average person can only keep 7 (plus or minus 2) items in their working memory. KEY TAKEAWAYS Chunking is an effective method of presenting groups of content in a manageable way. Organize content in groups of 5-9 items at a time. ORIGINS In 1956, George Miller asserted that the span of immediate memory and absolute judgment were both limited to around 7 pieces of information. The main unit of information is the bit, the amount of data necessary to make a choice between two equally likely alternatives. Likewise, 4 bits of information is a decision between 16 binary alternatives (4 successive binary decisions). The point where confusion creates an incorrect judgment is the channel capacity. In other words, the quantity of bits which can be transmitted reliably through a channel, within a certain amount of time.
Law of Similarity
OVERVIEW The human eye tends to perceive similar elements in a design as a complete picture, shape, or group, even if those elements are separated. KEY TAKEAWAYS Ensure that links and navigation systems are visually differentiated from normal text elements, and are consistently styled. ORIGINS The principles of grouping (or Gestalt laws of grouping) are a set of principles in psychology, first proposed by Gestalt psychologists to account for the observation that humans naturally perceive objects as organized patterns and objects, a principle known as Prägnanz. Gestalt psychologists argued that these principles exist because the mind has an innate disposition to perceive patterns in the stimulus based on certain rules. These principles are organized into five categories: Proximity, Similarity, Continuity, Closure, and Connectedness.
Hick's Law
OVERVIEW The time it takes to make a decision increases with the number and complexity of choices. KEY TAKEAWAYS Simplify choices for the user by breaking down complex tasks into smaller steps. Avoid overwhelming users by highlighting recommended options. Use progressive onboarding to minimize cognitive load for new users. ORIGINS Hick's Law (or the Hick-Hyman Law) is named after a British and an American psychologist team of William Edmund Hick and Ray Hyman. In 1952, this pair set out to examine the relationship between the number of stimuli present and an individual's reaction time to any given stimulus. As you would expect, the more stimuli to choose from, the longer it takes the user to make a decision on which one to interact with. Users bombarded with choices have to take time to interpret and decide, giving them work they don't want.
Fitts's Law
OVERVIEW 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 both discern what it is and to accurately select them. Touch targets should have ample spacing between each other. Touch targets should be placed in areas of an interface that allows them to be easily acquired. ORIGINS In 1954, psychologist Paul Fitts, examining the human motor system, showed that the time required to move to a target depends on the distance to it, yet relates inversely to its size. By his law, fast movements and small targets result in greater error rates, due to the speed-accuracy trade-off. Although multiple variants of Fitts' law exist, all encompass this idea. Fitts' law is widely applied in user experience (UX) and user interface (UI) design. For example, this law influenced the convention of making interactive buttons large (especially on finger-operated mobile devices)—smaller buttons are more difficult (and time-consuming) to click. Likewise, the distance between a user's task/attention area and the task-related button should be kept as short as possible.
Serial Position Effect
OVERVIEW Users have a propensity to best remember the first and last items in a series. KEY TAKEAWAYS Placing the least important items in the middle of lists can be helpful because these items tend to be stored less frequently in long-term and working memory. Positioning key actions on the far left and right within elements such as navigation can increase memorization. ORIGINS The serial position effect, a term coined by Herman Ebbinghaus, describes how the position of an item in a sequence affects recall accuracy. The two concepts involved, the primacy effect and the recency effect, explains how items presented at the beginning of a sequence and the end of a sequence are recalled with greater accuracy than items in the middle of a list. Manipulation of the serial position effect to create better user experiences is reflected in many popular designs by successful companies like Apple, Electronic Arts, and Nike.
Aesthetic Usability Effect
OVERVIEW Users often perceive aesthetically pleasing design as design that's more usable. KEY TAKEAWAYS Aesthetically pleasing design can make users more tolerant of minor usability issues. Aesthetically pleasing design creates a positive response in people's brains and leads them to believe the design actually works better. Aesthetically pleasing design can mask usability problems and prevent issues from being discovered during usability testing. ORIGINS The aesthetic-usability effect was first studied in the field of human-computer interaction in 1995. Researchers Masaaki Kurosu and Kaori Kashimura from the Hitachi Design Center tested 26 variations of an ATM UI, asking the 252 study participants to rate each design on ease of use, as well as aesthetic appeal. They found a stronger correlation between the participants' ratings of aesthetic appeal and perceived ease of use than the correlation between their ratings of aesthetic appeal and actual ease of use. Kurosu and Kashimura concluded that users are strongly influenced by the aesthetics of any given interface, even when they try to evaluate the underlying functionality of the system.
Jakob's Law
OVERVIEW Users spend most of their time on other sites. This means that users 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 user can focus on their task rather than learning new models. Minimize discordance by empowering users to continue using a familiar version for a limited time. ORIGINS Jakob's Law was coined by Jakob Nielsen, a User Advocate and principal of the Nielsen Norman Group which he co-founded with Dr. Donald A. Norman (former VP of research at Apple Computer). Dr. Nielsen established the 'discount usability engineering' movement for fast and cheap improvements of user interfaces and has invented several usability methods, including heuristic evaluation.
