The Design of Everyday things

By Donald A. Norman

Highlights:

Good design is actually a lot harder to notice than poor design, in part because good designs fit our needs so well that the design is invisible, serving us without drawing attention to itself. Bad design, on the other hand, screams out its inadequacies, making itself very noticeable.

Two of the most important characteristics of good design are discoverability and understanding.

Engineers still tend to believe in logic. They often explain to me in great, logical detail, why their designs are good, powerful, and wonderful.“Why are people having problems?” they wonder.“You are being too logical,” I say.“You are designing for people the way you would like them to be, not for the way they really are. ”

Discoverability results from appropriate application of five fundamental psychological concepts covered in the next few chapters: affordances, signifiers, constraints, mappings, and feedback. But there is a sixth principle, perhaps most important of all: the conceptual model of the system.

An affordance is a relationship between the properties of an object and the capabilities of the agent that determine just how the object could possibly be used. A chair affords (“is for”) support and, therefore, affords sitting.

Affordances determine what actions are possible. Signifiers communicate where the action should take place

Profound ideas are always obvious once they are understood.

Simplified models are valuable only as long as the assumptions that support them hold true.

The designer expects the user’s model to be identical to the design model, but because designers cannot communicate directly with users, the entire burden of communication is on the system image

The same technology that simplifies life by providing more functions in each device also complicates life by making the device harder to learn, harder to use. This is the paradox of technology and the challenge for the designer.

When people use something, they face two gulfs: the Gulf of Execution, where they try to figure out how it operates, and the Gulf of Evaluation, where they try to figure out what happened (Figure 2.1). The role of the designer is to help people bridge the two gulfs.

How do we know what we do not know so rapidly? Yet some things that we do know can take a long time to retrieve. For example, answer this: In the house you lived in three houses ago, as you entered the front door, was the doorknob on the left or right?

Emotion is highly underrated. In fact, the emotional system is a powerful information processing system that works in tandem with cognition. Cognition attempts to make sense of the world: emotion assigns value

Great designers use their aesthetic sensibilities to drive these visceral responses

One nasty experience with a service provider can spoil all future experiences. One superb experience can make up for past deficiencies.

The problem is that once failure starts, it is soon generalized by self-blame to all of mathematics. Similar processes are at work with technology. The vicious cycle starts: if you fail at something, you think it is your fault. Therefore you think you can’t do that task. As a result, next time you have to do the task, you believe you can’t, so you don’t even try. The result is that you can’t, just as you thought. You’re trapped in a self-fulfilling prophecy.

Do not blame people when they fail to use your products properly. • Take people’s difficulties as signifiers of where the product can be improved

Eliminate all error messages from electronic or computer systems.Instead, provide help and guidance. • Make it possible to correct problems directly from help and guidance messages. Allow people to continue with their task: Don’t impede progress — help make it smooth and continuous. Never make people start over. • Assume that what people have done is partially correct, so if it is inappropriate, provide the guidance that allows them to correct the problem and be on their way. • Think positively, for yourself and for the people you interact with

human error usually is a result of poor design: it should be called system error. Humans err continually; it is an intrinsic part of our nature. System design should take this into account. Pinning the blame on the person may be a comfortable way to proceed, but why was the system ever designed so that a single act by a single person could cause calamity

Normally, people do not need precision in their judgments. All that is needed is the combination of knowledge in the world and in the head that makes decisions unambiguous.

CONSTRAINTS SIMPLIFY MEMORY Before widespread literacy, and especially before the advent of sound recording devices, performers traveled from village to village, reciting epic poems thousands of lines long. This tradition still exists in some societies. How do people memorize such voluminous amounts of material? Do some people have huge amounts of knowledge in their heads? Not really. It turns out that external constraints exert control over the permissible choice of words, thus dramatically reducing the memory load. One of the secrets comes from the powerful constraints of poetry
including rhyme, rhythm, meter, assonance, alliteration, and onomatopoeia

The more complex the password requirements, the less secure the system.Why? Because people, unable to remember all these combinations, write them down. And then where do they store this private, valuable knowledge? In their wallet, or taped under the computer keyboard, or wherever it is easy to find, because it is so frequently needed. So a thief only has to steal the wallet or find the list and then all secrets are known. Most people are honest, concerned workers. And it is these individuals that complex security systems impede the most, preventing them from getting their work done. As a result, it is often the most dedicated employee who violates the security rules and weakens the overall system

To maximize efficiency of working memory it is best to present different information over different modalities: sight, sound, touch (haptics), hearing, spatial location, and gestures. Automobiles should use auditory presentation of driving instructions and haptic vibration of the appropriate side of the driver’s seat or steering wheel to warn when drivers leave their lanes, or when there are other vehicles to the left or right, so as not to interfere with the visual processing of driving information. Driving is primarily visual, so the use of auditory and haptic modalities minimizes interference with the visual task.

This is why when you search for a name but continually retrieve the wrong name, you know it is wrong. Because this false retrieval impedes the correct retrieval, you have to turn to some other activity to allow the subconscious memory retrieval process to reset itself.

A huge number of psychological experiments show how easy it is to implant false memories into people’s minds so convincingly that people refuse to admit that the memory is of an event that never happened

The design implications are clear: provide meaningful structures. Perhaps a better way is to make memory unnecessary: put the required information in the world. This is the power of the traditional graphical user interface with its old-fashioned menu structure

It is a profoundly erroneous truism, repeated by all copy-books and by eminent people when they are making speeches, that we should cultivate the habit of thinking of what we are doing. The precise opposite is the case. Civilization advances by extending the number of important operations which we can perform without thinking about them.

There are five memory slots in short-term memory. Each time a new item is added, it occupies a slot, knocking out whatever was there beforehand. Is this model true? No, not a single memory researcher in the entire world believes this to be an accurate model of STM. But it is good enough for applications. Make use of this model, and your designs will be more usable

Science strives for truth. As a result, scientists are always debating, arguing, and disagreeing with one another. The scientific method is one of debate and conflict. Only ideas that have passed through the critical examination of multiple other scientists survive. This continual disagreement often seems strange to the nonscientist, for it appears that scientists don’t know anything.

The air-traffic control system is evolving to help. The instructions from the air-traffic controllers will be sent digitally, so that they can remain displayed on a screen as long as the pilot wishes. The digital transmission also makes it easy for automated equipment to set itself to the correct parameters. Digital transmission of the controller’s commands has some disadvantages, however. Other aircraft will not hear the commands, which reduces pilot awareness of what all the airplanes in the vicinity are going to do. Researchers in air-traffic control and aviation safety are looking into these issues.Yes, it’s a design issue.

Just as in doing an action we can distinguish between knowing what can be done and knowing how to do it, in reminding we must distinguish between the signal — knowing that something is to be remembered, and the message — remembering the information itself

Knowledge in the world acts as its own reminder. It can help us recover structures that we otherwise would forget. Knowledge in the head is efficient: no search and interpretation of the environment is required

TABLE 3.1. Tradeoffs Between Knowledge in the World and in the HeadKnowledge in the World Knowledge in the Head Information is readily and easily Material in working memory is readavailable whenever perceivable. ily available. Otherwise considerable search and effort may be required. Interpretation substitutes for Requires learning, which can be learning. How easy it is to interpret considerable. Learning is made knowledge in the world depends easier if there is meaning or upon the skill of the designer. structure to the material or if there is a good conceptual model. Slowed by the need to find and Can be efficient, especially if so interpret the knowledge.well-learned that it is automated. Ease of use at first encounter is high. Ease of use at first encounter is low. Can be ugly and inelegant, Nothing needs to be visible, which especially if there is a need to gives more freedom to the designer. maintain a lot of knowledge. This This leads to cleaner, more pleascan lead to clutter. Here is where the ing appearance — at the cost of ease skills of the graphics and industrial of use at first encounter, learning, designer play major roles. and remembering. 110 The Design of Everyday Things

Constraints are powerful clues, limiting the set of possible actions. The thoughtful use of constraints in design lets people readily determine the proper course of action, even in a novel situation

When cars become fully automated, communicating among themselves with wireless networks, what will be the meaning of the red lights on the rear of the auto? That the car is braking? But for whom would the signal be intended? The other cars would already know. The red light would become meaningless, so it could either be removed or it could be redefined to indicate some other condition.
pause the video in order to make a comment or answer a question.Activity

The difficulty with activity-based controllers is handling the exceptional cases, the ones not thought about during design.Activity-centered controls are the proper way to go, if the activities are carefully selected to match actual requirements. But even in these cases, manual controls will still be required because there will always be some new, unexpected demand that requires idiosyncratic settings. As my example demonstrates, invoking the manual settings should not cause the current activity to be canceled.

Affordances refer to the potential actions that are possible, but these are easily discoverable only if they are perceivable: perceived affordances. It is the signifier component of the perceived affordance that allows people to determine the possible actions. But how does one go from the perception of an affordance to understanding the potential action? In many cases, through conventions.

Standardization is indeed the fundamental principle of desperation: when no other solution appears possible, simply design everything the same way, so people only have to learn once.

The use of sound to convey knowledge is a powerful and important idea, but still in its infancy

If the system lets you make the error, it is badly designed. And if the system induces you to make the error, then it is really badly designed

People are creative, constructive, exploratory beings. We are particularly good at novelty, at creating new ways of doing things, and at seeing new opportunities.Dull, repetitive, precise requirements fight against these traits. We are alert to changes in the environment, noticing new things, and then thinking about them and their implications. These are virtues, but they get turned into negative features when we are forced to serve machines. Then we are punished for lapses in attention, for deviating from the tightly prescribed routines

It is tempting to save money and space by having a single control serve multiple purposes. Suppose there are ten different functions on a device. Instead of using ten separate knobs or switches — which would take considerable space, add extra cost, and appear intimidatingly complex, why not use just two controls, one to select the function, the other to set the function to the desired condition? Although the resulting design appears quite simple and easy to use, this apparent simplicity masks the underlying complexity of use

Mode errors are especially likely where the equipment does not make the mode visible, so the user is expected to remember what mode has been established, sometimes hours earlier, during which time many intervening events might have occurred. Designers must try to avoid modes, but if they are necessary, the equipment must make it obvious which mode is invoked.

Skill-based behavior occurs when workers are extremely expert at their jobs, so they can do the everyday, routine tasks with little or no thought or conscious attention. The most common form of errors in skill-based behavior is slips.Rule-based behavior occurs when the normal routine is no longer applicable but the new situation is one that is known, so there is already a well-prescribed course of action: a rule. Rules simply might be learned behaviors from previous experiences, but includes formal procedures prescribed in courses and manuals, usually in the form of “if-then” statements, such as, “If the engine will not start, then do [the appropriate action]. ” Errors with rule-based behavior can be either a mistake or a slip. If the wrong rule is selected, this would be a mistake. If the error occurs during the execution of the rule, it is most likely a slip.Knowledge-based procedures occur when unfamiliar events occur, where neither existing skills nor rules apply. In this case, there must be considerable reasoning and problem-solving. Plans might be developed, tested, and then used or modified.Here, conceptual models are essential in guiding development of the plan and interpretation of the situation.

Hindsight is always superior to foresight. When the accident investigation committee reviews the event that contributed to the problem, they know what actually happened, so it is easy for them to pick out which information was relevant, which was not

The design challenge is to present the information about the state of the system (a device, vehicle, plant, or activities being monitored) in a way that is easy to assimilate and interpret, as well as to provide alternative explanations and interpretations. It is useful to question decisions, but impossible to do so if every action — or failure to act — requires close attention. This is a difficult problem with no obvious solution

The difficulties here are in establishing the interaction of the people with the automation: human teams and automated systems have to be thought of as collaborative, cooperative systems.Instead, they are often built by assigning the tasks that machines can do to the machines and leaving the humans to do the rest

How can we overcome these kinds of social problems? Good design alone is not sufficient. We need different training; we need to reward safety and put it above economic pressures

A collaboratively followed checklist is an effective way to counteract these natural human tendencies.

Distinguishing a true anomaly from an apparent one is difficult.

Understand the causes of error and design to minimize those causes. • Do sensibility checks. Does the action pass the “common sense” test? • Make it possible to reverse actions — to “undo” them — or make it harder to do what cannot be reversed. • Make it easier for people to discover the errors that do occur, and make them easier to correct. • Don’t treat the action as an error; rather, try to help the person complete the action properly. Think of the action as an approximation to what is desired.

Make the item being acted upon more prominent. That is, change the appearance of the actual object being acted upon to be more visible: enlarge it, or perhaps change its color. • Make the operation reversible. If the person saves the content, no harm is done except the annoyance of having to reopen the file. If the person elects Don’t Save, the system could secretly save the contents, and the next time the person opened the file, it could ask whether it should restore it to the latest condition.

The Swiss cheese metaphor suggests several ways to reduce accidents: • Add more slices of cheese. • Reduce the number of holes (or make the existing holes smaller). • Alert the human operators when several holes have lined up.

When the automation works, the tasks are usually done as well as or better than by people.Moreover, it saves people from the dull, dreary routine tasks, allowing more useful, productive use of time, reducing fatigue and error. But when the task gets too complex, automation tends to give up.This, of course, is precisely when it is needed the most. The paradox is that automation can take over the dull, dreary tasks, but fail with the complex ones

We expect people to monitor machines, which means keeping alert for long periods, something we are bad at. We require people to do repeated operations with the extreme precision and accuracy required by machines, again something we are not good at. When we divide up the machine and human components of a task in this way, we fail to take advantage of human strengths and capabilities but instead rely upon areas where we are genetically, biologically unsuited

Put the knowledge required to operate the technology in the world. Don’t require that all the knowledge must be in the head. Allow for efficient operation when people have learned all the requirements, when they are experts who can perform without the knowledge in the world, but make it possible for non-experts to use the knowledge in the world. This will also help experts who need to perform a rare, infrequently performed operation or return to the technology after a prolonged absence. • Use the power of natural and artificial constraints: physical, logical, semantic, and cultural. Exploit the power of forcing functions and natural mappings. • Bridge the two gulfs, the Gulf of Execution and the Gulf of Evaluation. Make things visible, both for execution and evaluation. On the execution side, provide feedforward information: make the options readily available. On the evaluation side, provide feedback: make the results of each action apparent. Make it possible to determine the system’s status readily, easily, accurately, and in a form consistent with the person’s goals, plans, and expectations

Engineers and businesspeople are trained to solve problems. Designers are trained to discover the real problems. A brilliant solution to the wrong problem can be worse than no solution at all: solve the correct problem

HCD is a procedure for addressing these requirements, but with an emphasis on two things: solving the right problem, and doing so in a way that meets human needs and capabilities.

This repeated divergence and convergence is important in properly determining the right problem to be solved and then the best way to solve it. It looks chaotic and ill-structured, but it actually follows well-established principles and procedures.

Design wants to know what people really need and how they actually will use the product or service under consideration. Marketing wants to know what people will buy, which includes learning how they make their purchasing decisions

Customer research is a tradeoff: deep insights on real needs from a tiny set of people, versus broad, reliable purchasing data from a wide range and large number of people. We need both. Designers understand what people really need.

How can we pretend to accommodate all of these very different, very disparate people? The answer is to focus on activities, not the individual person. I call this activity-centered design. Let the activity define the product and its structure. Let the conceptual model of the product be built around the conceptual model of the activity

there is a difference between task and activity. I emphasize the need to design for activities: designing for tasks is usually too restrictive. An activity is a high-level structure, perhaps “go shopping. ” A task is a lower-level component of an activity, such as “drive to the market,” “find a shopping basket,” “use a shopping list to guide the purchases,” and so forth.

A major benefit is that if the design requirements are consistent with their activities, people will tolerate complexity and the requirements to learn something new: as long as the complexity andsix: Design Thinking 233

The iterative method, however, is best suited for the early design phases of a product, not for the later stages

Sometimes this is not even possible because critical knowledge about project decisions and methods are in the form we call implicit knowledge; that is, within the heads of the workers. When workers leave, their implicit knowledge goes with them

The day a product development process starts, it is behind schedule and above budget.

Each of the separate disciplines has a different view of the product, each has different but specific requirements to be met. Often the requirements posed by each discipline are contradictory or incompatible with those of the other disciplines. But all of them are correct when viewed from their respective perspective. In most companies, however, the disciplines work separately, design passing its results to engineering and programming, which modify the requirements to fit their needs. They then pass their results to manufacturing, which does further modification, then marketing requests changes. It’s a mess.

Producing a good product requires a lot more than good technical skills: it requires a harmonious, smoothly functioning, cooperative and respectful organization.

Designers need to understand their customers, and in many cases, the customer is the person who purchases the product, not the person who actually uses it.

There must be a multidisciplinary team overseeing the entire design, engineering, and manufacturing process that shares all departmental issues and concerns from day one, so that everyone can design to satisfy them, and when conflicts arise, the group together can determine the most satisfactory solution.Sadly, it is the rare company that is organized this way.

One device simply cannot work for everyone. Even such simple tools as pencils need to be designed differently for different activities and types of people

Of all the devices intended to aid the elderly, perhaps the most shunned is the walker. Most of these devices are ugly. They cry out, “Disability here. ” Why not transform them into products to be proud of?

The best solution to the problem of designing for everyone is flexibility: flexibility in the size of the images on computer screens, in the sizes, heights, and angles of tables and chairs. Allow people to adjust their own seats, tables, and working devices. Allow them to adjust lighting, font size, and contrast.

Complex things are no longer complicated once they are understood.

In her book Different, Harvard professor Youngme Moon argues that it is this attempt to match the competition that causes all products to be the same

Numerous small companies tried to manufacture screens, but the first devices that could handle multiple touches were either very expensive or unreliable.

Inventors often believe their new ideas will revolutionize the world in months, but reality is harsher. Most new inventions fail, and even the few that succeed take decades to do so.

Thinking of the concept of a video connection was relatively easy. Thinking through the details has been very difficult, and then being able to build it and put it into practice

. Moving the R and P from the fourth row to the second makes it possible to type the word typewriter using only keys on the second

Evolutionary change to people is always taking place, but the pace of human evolutionary change is measured in thousands of years. Human cultures change somewhat more rapidly over periods measured in decades or centuries.Microcultures, such as the way by which teenagers differ from adults, can change in a generation. What this means is that although technology is continually introducing new means of doing things, people are resistant to changes in the way they do things282 The Design of Everyday Things

People often ask me to predict “the next great change. ” My answer is to tell them to examine some fundamentals, such as social interaction, communication, sports and play, music and entertainment. The changes will take place within spheres of activity such as these. Are these the only fundamentals? Of course not: add education (and learning), business (and commerce), transportation, self-expression, the arts, and of course, sex. And don’t forget important sustaining activities, such as the need for good health, food and drink, clothing, and housing. Fundamental needs will also stay the same, even if they get satisfied in radically different ways

In Western cultures, design has reflected the capitalistic importance of the marketplace, with an emphasis on exterior features deemed to be attractive to the purchaser. In the consumer economy, taste is not the criterion in the marketing of expensive foods or drinks, usability is not the primary criterion in the marketing of home and office appliances. We are surrounded with objects of desire, not objects of use.

These are two different sets of requirements: design must satisfy both. It doesn’t matter how great the design is if people don’t buy it. And it doesn’t matter how many people buy something if they are going to dislike it when they start using it