The Design of Everyday Things: Revised and Expanded Edition

✏️ Highlights

The book could be read quickly as a basic, general introduction.

principles of human psychology will remain the same,

The first edition had a focus upon affordances, but although affordances make sense for interaction with physical objects, they are confusing when dealing with virtual ones.

affordances have created much confusion in the world of design.

Affordances define what actions are possible.

Signifiers specify how people discover those possibilities: signifiers are signs, perceptible signals of what can be done.

Signifiers are of far more importance to designers than are affordances. Hence, the extended treatment.

to 2038, I had to be careful to choose examples that would not

Chapter 1: The Psychopathology of Everyday Things

Chapter 2: The Psychology of Everyday Actions

In this chapter I show the interplay between these two, show that different emotions arise at the different stages, and show which stages are primarily located at each of the three levels of processing (visceral, for the elementary levels of motor action performance and perception; behavioral, for the levels of action specification and initial interpretation of the outcome; and reflective,

Chapter 3: Knowledge in the Head and in the World

The section examines the way different cultures view time—the discussion might surprise you.

most important addition to this chapter is a section on culture,

Chapter. 4: Knowing What to Do: Constraints, Discoverability, and Feedback

how change can be extremely disconcerting, even to professionals, even if the change is for the better.

The chapter concludes with a quick discussion of the difficulties posed by automation (from my book The Design of Future Things)

Chapter 5: Human Error? No, Bad Design

In particular, I now divide slips into two main categories—action-based and memory lapses; and mistakes into three categories—rule-based, knowledge-based, and memory lapses. (These distinctions are now common, but I introduce a slightly different way to treat memory lapses.)

Chapter 6: Design Thinking

I discuss two views of human-centered design: the British Design Council’s double-diamond model and the traditional HCD iteration of observation, ideation, prototyping, and testing.

“What I Just Told You? It Doesn’t Really Work That Way.” Here is where I introduce Norman’s Law: The day the product team is announced, it is behind schedule and over its budget.

challenges of design within a company, where schedules, budgets, and the competing requirements of the different divisions all provide severe constraints upon what can be accomplished.

Chapter 7: Design in the World of Business

Everyone wants radical innovation, but the truth is, most radical innovations fail, and even when they do succeed, it can take multiple decades before they are accepted.

The techniques of human-centered design are appropriate to incremental innovation: they cannot lead to radical innovations.

the moral obligations of design, and the rise of small, do-it-yourself makers that are starting to revolutionize the way ideas are conceived and introduced into the marketplace: “the rise of the small,” I call it.

The Psychology of Everyday Things was appropriate for the twentieth century: The Design of Everyday Things is for the twenty-first. Don Norman Silicon Valley, California

I were placed in the cockpit of a modern jet airliner, my inability to perform well would neither surprise nor bother me. But why should I have trouble with doors and light switches, water faucets and stoves?

“Doors?” I can hear the reader saying. “You have trouble opening doors?” Yes. I push doors that are meant to be pulled, pull doors that should be pushed, and walk into doors that neither pull nor push, but slide.

My problems with doors have become so well known that confusing doors are often called “Norman doors.” Imagine becoming famous for doors that don’t work right.

When there is understanding it can lead to a feeling of control, of mastery, and of satisfaction or even pride—all strong positive emotions.

We live in a world filled with objects, many natural, the rest artificial. Every day we encounter thousands of objects, many of them new to us.

Why is it that when we encounter many unusual natural objects, we know how to interact with them? Why is this true with many of the artificial, human-made objects we encounter? The answer lies with a few basic principles. Some of the most important of these principles come from a consideration of affordances. The term affordance refers to the relationship between a physical object and a person (or for that matter, any interacting agent, whether animal or human, or even machines and robots).

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. Most chairs can also be carried by a single person (they afford lifting), but some can only be lifted by a strong person or by a team of people.

Glass affords transparency. At the same time, its physical structure blocks the passage of most physical objects. As a result, glass affords seeing through and support, but not the passage of air or most physical objects (atomic particles can pass through glass). The blockage of passage can be considered an anti-affordance—the prevention of interaction.

To be effective, affordances and anti-affordances have to be discoverable—perceivable. This poses a difficulty with glass. The reason we like glass is its relative invisibility, but this aspect, so useful in the normal window, also hides its anti-affordance property of blocking passage. As a result, birds often try to fly through windows. And every year, numerous people injure themselves when they walk (or run) through closed glass doors or large picture windows.

signaling its presence is required: I call this property a signifier (discussed in the next section).

The notion of affordance and the insights it provides originated with J. J. Gibson, an eminent psychologist who provided many advances to our understanding of human perception.

We disagreed about almost everything. I was an engineer who became a cognitive psychologist, trying to understand how the mind works. He started off as a Gestalt psychologist, but then developed an approach that is today named after him: Gibsonian psychology, an ecological approach to perception.

He argued that the world contained the clues and that people simply picked them up through “direct perception.” I argued that nothing could be direct: the brain had to process the information arriving at the sense organs to put together a coherent interpretation. “Nonsense,” he loudly proclaimed; “it requires no interpretation: it is directly perceived.”

Gibson believed that the combined information picked up by all of our sensory apparatus—sight, sound, smell, touch, balance, kinesthetic, acceleration, body position— determines our perceptions without the need for internal processing or cognition.

the physical objects conveyed important information about how people could interact with them, a property he named “affordance.”

Affordances exist even if they are not visible. For designers, their visibility is critical: visible affordances provide strong clues to the operations of things. A flat plate mounted on a door affords pushing.

Knobs afford turning, pushing, and pulling. Slots are for inserting things into. Balls are for throwing or bouncing. Perceived affordances help people figure out what actions are possible without the need for labels or instructions.

the term became used in ways that had nothing to do with the original.

mention of the term everywhere. Alas,

Many people find affordances difficult to understand because they are relationships, not properties.

They soon discovered that when working with the graphical designs for electronic displays, they needed a way to designate which parts could be touched, slid upward, downward, or sideways, or tapped upon. The actions could be done with a mouse, stylus, or fingers. Some systems responded to body motions, gestures, and spoken words, with no touching of any physical device. How could designers describe what they were doing?

There was no word that fit, so they took the closest existing word—affordance. Soon designers were saying such things as, “I put an affordance there,” to describe why they displayed a circle on a screen to indicate where the person should touch, whether by mouse or by finger.

“that is not an affordance. That is a way of communicating where the touch should be. You are communicating where to do the touching: the affordance of touching exists on the entire screen: you are trying to signify where the touch should take place. That’s not the same thing as saying what action is possible.”

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

1.4.The Sink That Would Not Drain: Where Signifiers Fail. I washed my hands in my hotel sink in London, but then, as shown in Photo A, was left with the question of how to empty the sink of the dirty water. I searched all over for a control: none.

This wall, at the Industrial Design department of KAIST, in Korea, provides an anti-affordance, preventing people from falling down the stair shaft. Its top is flat, an accidental by-product of the design. But flat surfaces afford support, and as soon as one person discovers it can be used to dispose of empty drink containers, the discarded container becomes a signifier,

This wall, at the Industrial Design department of KAIST, in Korea, provides an anti-affordance, preventing people from falling down the stair shaft. Its top is flat, an accidental by-product of the design. But flat surfaces afford support, and as soon as one person discovers it can be used to dispose of empty drink containers, the discarded container becomes a signifier, telling others that it is permissible to discard their items there.

•Affordances are the possible interactions between people and the environment.

Whenever you see hand-lettered signs pasted on doors, switches, or products, trying to explain how to work them, what to do and what not to do, you are also looking at poor design.

A designer approaches his mentor. He is working on a system that recommends restaurants to people, based upon their preferences and those of their friends. But in his tests, he discovered that people never used all of the features. “Why not?” he asks his mentor. (With apologies to Socrates.)

DESIGNER MENTOR I’m frustrated; people aren’t using our application properly. Can you tell me about it?

military tanks that have tracks instead of wheels use separate controls for the speed and direction of each track: to turn right, the left track is increased in speed, while the right track is slowed or even reversed. This is also how a wheelchair is steered.

Natural mapping, by which I mean taking advantage of spatial analogies, leads to immediate understanding. For example, to move an object up, move the control up. To make it easy to determine which control works which light in a large room or auditorium,

Other natural mappings follow from the principles of perception and allow for the natural grouping or patterning of controls and feedback.

In Chapter 3, I discuss how different cultures view time, which has important implications for some kinds of mappings.

Ever drive to a traffic intersection and wait an inordinate amount of time for the signals to change, wondering all the time whether the detection circuits noticed your vehicle (a common problem with bicycles)? What is missing in all these cases is feedback: some way of letting you know that the system is working on your request.

Given the importance of feedback, it is amazing how many products ignore it.

Poor feedback can be worse than no feedback at all, because it is distracting, uninformative, and in many cases irritating and anxiety-provoking.

Too much feedback can be even more annoying than too little. My dishwasher likes to beep at three a.m. to tell me that the wash is done, defeating my goal of having it work in the middle of the night so as not to disturb anyone (and to use less expensive electricity).

Machines that give too much feedback are like backseat drivers. Not only is it distracting to be subjected to continual flashing lights, text announcements, spoken voices, or beeps and boops, but it can be dangerous.

Poor design of feedback can be the result of decisions aimed at reducing costs, even if they make life more difficult for people.

focus upon cost reduction forces the design to use a single light or sound to convey multiple types of information.

Feedback is essential, but it has to be done correctly. Appropriately.

Hospital operating rooms, emergency wards. Nuclear power control plants. Airplane cockpits. All can become confusing, irritating, and life-endangering places because of excessive feedback, excessive alarms, and incompatible message coding.

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

Mental models, as the name implies, are the conceptual models in people’s minds that represent their understanding of how things work.

Consider a pair of scissors: you can see that the number of possible actions is limited. The holes are clearly there to put something into, and the only logical things that will fit are fingers. The holes are both affordances—they allow the fingers to be inserted—and signifiers—they indicate where the fingers are to go.

the buttons have multiple ways of being used. Two of the buttons do different things when pushed quickly or when kept depressed for several seconds.

Conceptual models are valuable in providing understanding, in predicting how things will behave, and in figuring out what to do when things do not go as planned.

A good conceptual model allows us to predict the effects of our actions. Without a good model, we operate by rote, blindly; we do operations as we were told to do them;

When things go wrong, however, or when we come upon a novel situation, then we need a deeper understanding, a good model.

used to own an ordinary, two-compartment refrigerator—nothing very fancy about it. The problem was that I couldn’t set the temperature properly.

Or perhaps our devices won’t have displays, but will quietly whisper the results into our ears,

The devices will be able to do many useful things, but I fear they will also frustrate: so many things to control, so little space for controls or signifiers. The obvious solution is to use exotic gestures or spoken commands, but how will we learn, and then remember, them?

A few decades ago, watches were simple. All you had to do was set the time and keep the watch wound. The standard control was the stem: a knob at the side of the watch. Turning the knob would wind the spring that provided power to the watch movement.

Watches in olden times were expensive instruments, manufactured by hand. They were sold in jewelry stores. Over time, with the introduction of digital technology, the cost of watches decreased rapidly, while their accuracy and reliability increased.

The hard part is to convince people to understand the viewpoints of the others, to abandon their disciplinary viewpoint and to think of the design from the viewpoints of the person who buys the product and those who use it, often different people. The viewpoint of the business is also important,

Interestingly, many people do experience difficulties, but explain them away by blaming themselves.

Most innovation is done as an incremental enhancement of existing products.

“People don’t want to buy a quarter-inch drill.

“People don’t want to buy a quarter-inch drill. They want a quarter-inch hole!”

Why not develop methods that don’t require holes? Or perhaps books that don’t require bookshelves. (Yes, I know: electronic books, e-books.)

Most people can determine the house, but have difficulty answering the question because they can readily imagine the doorknob on both sides of the door. The way to solve this problem is to imagine doing some activity, such as walking up to the front door while carrying heavy packages with both hands: how do you open the door?

Cognition and emotion cannot be separated. Cognitive thoughts lead to emotions: emotions drive cognitive thoughts.

Emotion is highly underrated. In fact, the emotional system is a powerful information processing system that works in tandem with cognition.

Cognition provides understanding: emotion provides value judgments. A human without a working emotional system has difficulty making choices.

Cognition attempts to make sense of the world: emotion assigns value.

Because much human behavior is subconscious—that is, it occurs without conscious awareness—we often don’t know what we are about to do, say, or think until after we have done it. It’s as if we had two minds: the subconscious and the conscious, which don’t always talk to each other.

In calm, nonthreatening situations, the emotional system triggers the release of hormones that relax the muscles and bias the brain toward exploration and creativity. Now the brain is more apt to notice changes in the environment, to be distracted by events, and to piece together events and knowledge that might have seemed unrelated earlier.

A positive emotional state is ideal for creative thought, but it is not very well suited for getting things done.

A positive emotional state is ideal for creative thought, but it is not very well suited for getting things done. Too much, and we call the person scatterbrained, flitting from one topic to another, unable to finish one thought before another comes to mind. A brain in a negative emotional state provides focus: precisely what is needed to maintain attention on a task and finish it. Too much, however, and we get tunnel vision, where people are unable to look

A positive emotional state is ideal for creative thought, but it is not very well suited for getting things done. Too much, and we call the person scatterbrained, flitting from one topic to another, unable to finish one thought before another comes to mind. A brain in a negative emotional state provides focus: precisely what is needed to maintain attention on a task and finish it. Too much, however, and we get tunnel vision, where people are unable to look beyond their narrow point of view.

This has nothing to do with how usable, effective, or understandable the product is. It is all about attraction or repulsion. Great designers use their aesthetic sensibilities to drive these visceral responses. Engineers and other logical people tend to dismiss the visceral response as irrelevant. Engineers are proud of the inherent quality of their work and dismayed when inferior products sell better “just because they look better.”

Reflection is cognitive, deep, and slow. It often occurs after the events have happened.

DESIGN MUST TAKE PLACE AT ALL LEVELS: VISCERAL, BEHAVIORAL, AND REFLECTIVE

THE BEHAVIORAL LEVEL The behavioral level is the home of learned skills, triggered by situations

FIGURE 2.3.Three Levels of Processing: Visceral, Behavioral, and Reflective. Visceral and behavioral levels are subconscious and the home of basic emotions. The reflective level is where conscious thought and decision-making reside, as well as the highest level of emotions.

To the designer, reflection is perhaps the most important of the levels of processing. Reflection is conscious, and the emotions produced at this level are the most protracted: those that assign agency and cause, such as guilt and blame or praise and pride. Reflective responses are part of our memory of events.

Reflective memories are often more important than reality. If we have a strongly positive visceral response but disappointing usability problems at the behavioral level, when we reflect back upon the product, the reflective level might very well weigh the positive response strongly enough to overlook the severe behavioral difficulties (hence the phrase, “Attractive things work better”). Similarly, too much frustration, especially toward the ending stage of use, and our reflections about the experience might overlook the positive visceral qualities.

Vacations are often remembered with fondness, despite the evidence from diaries of repeated discomfort and anguish.

One nasty experience with a service provider can spoil all future experiences. One superb experience can make up for past deficiencies. The behavioral level, which is the home of interaction, is also the home of all expectation-based emotions, of hope and joy, frustration and anger. Understanding arises at a combination of the behavioral and reflective levels. Enjoyment requires all three. Designing at all three levels is so important that I devote an entire book to the topic, Emotional Design. In psychology, there has been a long debate about which happens first: emotion or cognition. Do we run and flee because some

Most products do not cause fear, running, or fleeing, but badly designed devices can induce frustration and anger, a feeling of helplessness and despair, and possibly even hate.

Well-designed devices can induce pride and enjoyment, a feeling of being in control and pleasure—possibly even love and attachment.

Amusement parks are experts at balancing the conflicting responses of the emotional stages, providing rides and fun houses that trigger fear responses from the visceral and behavioral levels, while all the time providing reassurance at the reflective level that the park would never subject anyone to real danger.

expectations. When the results of our actions

One important emotional state is the one that accompanies complete immersion into an activity, a state that the social scientist Mihaly Csikszentmihalyi has labeled “flow.”

When in the flow state, people lose track of time and the outside environment. They are at one with the task they are performing.

The flow state occurs when the challenge of the activity just slightly exceeds our skill level, so full attention is continually required. Flow requires that the activity be neither too easy nor too difficult relative to our level of skill. The constant tension coupled with continual progress and success can be an engaging, immersive experience sometimes lasting for hours.

In the absence of external information, people can let their imagination run free as long as the conceptual models they develop account for the facts as they perceive them.

As a result, people use their thermostats inappropriately, causing themselves unnecessary effort, and often resulting in large temperature swings, thus wasting energy, which is both a needless expense and bad for the environment.

The tendency to repeat an action when the first attempt fails can be disastrous. This has led to numerous deaths when people tried to escape a burning building by attempting to push open exit doors that opened inward, doors that should have been pulled. As a result, in many countries, the law requires doors in public places to open outward, and moreover to be operated by so-called panic bars, so that they automatically open when people, in a panic to escape a fire, push their bodies against them. This is a great application of appropriate affordances: see the door in Figure 2.5.

The presence of a filling hourglass or rotating clock hands is a reassuring sign that work is in progress. When the delay can be predicted, some systems provide time estimates as well as progress bars to indicate how far along the task has gone.

Suppose I try to use an everyday thing, but I can’t. Who is at fault: me or the thing? We are apt to blame ourselves, especially if others are able to use it. Suppose the fault really lies in the device, so that lots of people have the same problems.

LEARNED HELPLESSNESS The phenomenon called learned helplessness might help explain the self-blame. It refers to the situation in which people experience repeated failure at a task. As a result, they decide that the task cannot be done, at least not by them: they are helpless. They stop trying. If this feeling covers a group of tasks, the result can be severe difficulties coping with life. In the extreme case, such learned helplessness leads to depression and to a belief that the individuals cannot cope with everyday life at all.

Sometimes all it takes to get such a feeling of helplessness are a few experiences that accidentally turn out bad. The phenomenon has been most frequently studied as a precursor to the clinical problem of depression, but I have seen it happen after a few bad experiences with everyday objects.

We could call this phenomenon taught helplessness. When people have trouble using technology, especially when they perceive (usually incorrectly) that nobody else is having the same problems, they tend to blame themselves. Worse, the more they have trouble, the more helpless they may feel, believing that they must be technically or mechanically inept. This is just the opposite of the more normal situation where people blame their own difficulties on the environment. This false blame is especially ironic because the culprit here is usually the poor design of the technology, so blaming the environment (the technology) would be completely appropriate.

Consider the normal mathematics curriculum, which continues relentlessly on its way, each new lesson assuming full knowledge and understanding of all that has passed before.

once you fall behind it is hard to catch up. The result: mathematics phobia—not because the material is difficult, but because it is taught so that difficulty in one stage hinders further progress.

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.

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.

We need to remove the word failure from our vocabulary, replacing it instead with learning experience.

With success, sure, we are pleased, but we often have no idea why we succeeded. With failure, it is often possible to figure out why, to ensure that it will never happen again.

One design firm, IDEO, has it as a creed: “Fail often, fail fast,” they say, for they know that each failure teaches them a lot about what to do right.

failures are an essential part of exploration and creativity. If designers and researchers

failures are an essential part of exploration and creativity. If designers and researchers do not sometimes fail, it is a sign that they are not trying hard enough—they are not thinking the great creative thoughts that will provide breakthroughs in how we do things. It is possible to avoid failure, to always be safe. But that is also the route to a dull, uninteresting life.

•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.

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.

how come nobody ever said anything about it? After all, they were encouraged to report all problems with the system. The reason was simple: when the system stopped working or did something strange, they dutifully reported it as a problem. But when they made the Return versus Enter error, they blamed themselves. After all, they had been told what to do. They had simply erred.

Eliminate the term human error. Instead, talk about communication and interaction: what we call an error is usually bad communication or interaction.

Today, we insist that people perform abnormally, to adapt themselves to the peculiar demands of machines, which includes always giving precise, accurate information. Humans are particularly bad at this, yet when they fail to meet the arbitrary, inhuman requirements

Today, we insist that people perform abnormally, to adapt themselves to the peculiar demands of machines, which includes always giving precise, accurate information. Humans are particularly bad at this, yet when they fail to meet the arbitrary, inhuman requirements of machines, we call it human error. No, it is design error. Designers should strive to minimize the chance of inappropriate actions in the first place by using affordances, signifiers, good mapping, and constraints to guide the actions.

People are subjected to continual interruptions. As a result, we are often bouncing back and forth between tasks, having to recover our place, what we were doing, and what we were thinking when we return to a previous task.

machines are programmed to be very fussy about the form of input they require, where the fussiness is not a requirement of the machine but due to the lack of consideration for people in the design of the software. In other words: inappropriate programming. Consider these examples. Many of us spend hours filling out forms on computers—forms that require names, dates, addresses, telephone numbers, monetary sums, and other information in a fixed, rigid format. Worse, often we are not even told the correct format until we get it wrong. Why not figure out the variety of ways a person might fill out a form and accommodate all of them? Some companies have done excellent jobs at this, so let us celebrate their actions. Consider Microsoft’s calendar program. Here, it is possible to specify dates any way you like: “November 23, 2015,” “23 Nov. 15,” or “11.23.15.” It even accepts phrases such as “a week from Thursday,” “tomorrow,” “a week from tomorrow,” or “yesterday.” Same with time. You can enter the time any way you want: “3:45 PM,” “15.35,” “an hour,” “two and one-half hours.” Same with telephone numbers: Want to start with a + sign (to indicate the code for international dialing)? No problem. Like to separate the number fields with spaces, dashes, parentheses, slashes, periods? No problem. As long as the program can decipher the date, time, or telephone number into a legal format, it is accepted. I hope the team that worked on this got bonuses and promotions. Although I single out Microsoft for being the pioneer in accepting a wide variety of formats, it is now becoming standard practice. By the time you read this, I would hope that every program would permit any intelligible format for names, dates, phone numbers, street addresses, and so on, transforming whatever is entered into whatever form the internal programming needs. But I predict that even in the twenty-second century, there will still be forms that require precise accurate (but arbitrary) formats for no reason

seven-stage model of the action cycle can be a valuable design tool, for it provides a basic checklist of questions to ask. In general, each stage of action

seven-stage model of the action cycle can be a valuable design tool, for it provides a basic checklist of questions to ask.

1.What do I want to accomplish? 2.What are the alternative action sequences? 3.What action can I do now? 4.How do I do it? 5.What happened? 6.What does it mean? 7.Is this okay? Have I accomplished my goal? FIGURE 2.7.The Seven Stages of Action as Design Aids. Each of the seven stages indicates a place where the person using the system has a question. The seven

1.Discoverability. It is possible to determine what actions are possible and the current state of the device. 2.Feedback. There is full and continuous information about the results of actions and the current state of the product or service. After an action has been executed, it is easy to determine the new state. 3.Conceptual model. The design projects all the information needed to create a good conceptual model of the system, leading to understanding and a feeling of control. The conceptual model enhances both discoverability and evaluation of results. 4.Affordances. The proper affordances exist to make the desired actions possible. 5.Signifiers. Effective use of signifiers ensures discoverability and that the feedback is well communicated and intelligible. 6.Mappings. The relationship between controls and their actions follows the principles of good mapping, enhanced as much as possible through spatial layout and temporal contiguity. 7.Constraints. Providing physical, logical, semantic, and cultural constraints guides actions and eases interpretation.

Ask yourself how the difficulty came about. Realize that many different groups of people might have been involved, each of which might have had intelligent, sensible reasons for their actions. For example, a troublesome bathroom shower was designed by people who were unable to know how it would be installed, then the shower controls might have been selected by a building contractor to fit the home plans provided by yet another person. Finally, a plumber, who may not have had contact with any of the other people, did the installation. Where did the problems arise? It could have been at any one (or several) of these stages. The result may appear to be poor design, but it may actually arise from poor communication.

One of my self-imposed rules is, “Don’t criticize unless you can do better.” Try to understand how the faulty design might have occurred: try to determine how it could have been done otherwise. Thinking about the causes and possible fixes to bad design should make you better appreciate good design.

next time you come across a well-designed object, one that you can use smoothly and effortlessly on the first try, stop and examine it.

Precise Behavior from Imprecise Knowledge Precise behavior can emerge from imprecise knowledge for four reasons:

1.Knowledge is both in the head and in the world.

2.Great precision is not required. Precision, accuracy, and completeness of knowledge are seldom required. Perfect behavior results if the combined knowledge in the head and in the world is sufficient to distinguish

2.Great precision is not required. Precision, accuracy, and completeness of knowledge are seldom required. Perfect behavior results if the combined knowledge in the head and in the world is sufficient to distinguish an appropriate choice from all others.

so much knowledge is available in the environment, it is surprising how little we need to learn. This is one reason people can function well in their environment and still be unable to describe what they do.

two kinds of knowledge: knowledge of and knowledge how. Knowledge of—what psychologists call declarative knowledge—includes the knowledge of facts and rules. “Stop at red traffic lights.” “New York City is north of Rome.” “China has twice as many people as India.” “To get the key out of the ignition of a Saab car, the gearshift must be in reverse.” Declarative knowledge is easy to write and to teach.

Knowledge how—what psychologists call procedural knowledge—is the knowledge that enables a person to be a skilled musician, to return a serve in tennis, or to move the tongue properly when saying the phrase “frightening witches.” Procedural knowledge is difficult or impossible to write down and difficult to teach.

it is much easier to memorize poetry than to create poems.

I am thinking of three words: one means “a mythical being,” the second is “the name of a building material,” and the third is “a unit of time.” What words do I have in mind?

The book could be read quickly as a basic, general introduction.

principles of human psychology will remain the same,

The first edition had a focus upon affordances, but although affordances make sense for interaction with physical objects, they are confusing when dealing with virtual ones.

affordances have created much confusion in the world of design.

Affordances define what actions are possible.

Signifiers specify how people discover those possibilities: signifiers are signs, perceptible signals of what can be done.

Signifiers are of far more importance to designers than are affordances. Hence, the extended treatment.

to 2038, I had to be careful to choose examples that would not

Chapter 1: The Psychopathology of Everyday Things

Chapter 2: The Psychology of Everyday Actions

In this chapter I show the interplay between these two, show that different emotions arise at the different stages, and show which stages are primarily located at each of the three levels of processing (visceral, for the elementary levels of motor action performance and perception; behavioral, for the levels of action specification and initial interpretation of the outcome; and reflective,

Chapter 3: Knowledge in the Head and in the World

The section examines the way different cultures view time—the discussion might surprise you.

most important addition to this chapter is a section on culture,

Chapter. 4: Knowing What to Do: Constraints, Discoverability, and Feedback

how change can be extremely disconcerting, even to professionals, even if the change is for the better.

The chapter concludes with a quick discussion of the difficulties posed by automation (from my book The Design of Future Things)

Chapter 5: Human Error? No, Bad Design

In particular, I now divide slips into two main categories—action-based and memory lapses; and mistakes into three categories—rule-based, knowledge-based, and memory lapses. (These distinctions are now common, but I introduce a slightly different way to treat memory lapses.)

Chapter 6: Design Thinking

I discuss two views of human-centered design: the British Design Council’s double-diamond model and the traditional HCD iteration of observation, ideation, prototyping, and testing.

“What I Just Told You? It Doesn’t Really Work That Way.” Here is where I introduce Norman’s Law: The day the product team is announced, it is behind schedule and over its budget.

challenges of design within a company, where schedules, budgets, and the competing requirements of the different divisions all provide severe constraints upon what can be accomplished.

Chapter 7: Design in the World of Business

Everyone wants radical innovation, but the truth is, most radical innovations fail, and even when they do succeed, it can take multiple decades before they are accepted.

The techniques of human-centered design are appropriate to incremental innovation: they cannot lead to radical innovations.

the moral obligations of design, and the rise of small, do-it-yourself makers that are starting to revolutionize the way ideas are conceived and introduced into the marketplace: “the rise of the small,” I call it.

The Psychology of Everyday Things was appropriate for the twentieth century: The Design of Everyday Things is for the twenty-first. Don Norman Silicon Valley, California

I were placed in the cockpit of a modern jet airliner, my inability to perform well would neither surprise nor bother me. But why should I have trouble with doors and light switches, water faucets and stoves?

“Doors?” I can hear the reader saying. “You have trouble opening doors?” Yes. I push doors that are meant to be pulled, pull doors that should be pushed, and walk into doors that neither pull nor push, but slide.

My problems with doors have become so well known that confusing doors are often called “Norman doors.” Imagine becoming famous for doors that don’t work right.

Two of the most important characteristics of good design are discoverability and understanding. Discoverability: Is it possible to even figure out what actions are possible and where and how to perform them? Understanding: What does it all mean? How is the product supposed to be used?

The doors in the story illustrate what happens when discoverability fails. Whether the device is a door or a stove, a mobile phone or a nuclear power plant, the relevant components must be visible, and they must communicate the correct message: What actions are possible? Where and how should they be done? With doors that push, the designer must provide signals that naturally indicate where to push. These need not destroy the aesthetics. Put a vertical plate on the side to be pushed. Or make the supporting pillars visible.

Many products defy understanding simply because they have too many functions and controls. I don’t think that simple home appliances—stoves, washing machines, audio and television sets—should look like Hollywood’s idea of a spaceship control room.

In England I visited a home with a fancy new Italian washer-dryer combination, with super-duper multisymbol controls, all to do everything anyone could imagine doing

husband (an engineering psychologist) said he refused to go near it. The wife (a physician) said she had simply memorized one setting and tried to ignore the rest.

The major areas of design relevant to this book are industrial design, interaction design, and experience design.

None of the fields is well defined, but the focus of the efforts does vary, with industrial designers emphasizing form and material, interactive designers emphasizing understandability and usability, and experience designers emphasizing the emotional impact. Thus:

Interaction design: The focus is upon how people interact with technology. The goal is to enhance people’s understanding of what can be done, what is happening, and what has just occurred. Interaction design draws upon principles of psychology, design, art, and emotion to ensure a positive, enjoyable experience. Experience design: The practice of designing products, processes, services, events, and environments with a focus placed on the quality and enjoyment of the total experience.

When people fail to follow these bizarre, secret rules, and the machine does the wrong thing, its operators are blamed for not understanding the machine, for not following its rigid specifications. With everyday objects, the result is frustration. With complex devices and commercial and industrial processes, the resulting difficulties can lead to accidents, injuries, and even deaths.

It is time to reverse the situation: to cast the blame upon the machines and their design. It is the machine and its design that are at fault.

The reasons for the deficiencies in human-machine interaction are numerous. Some come from the limitations of today’s technology. Some come from self-imposed restrictions by the designers, often to hold down cost. But most of the problems come from a complete lack of understanding of the design principles necessary for effective human-machine interaction.

Why this deficiency? Because much of the design is done by engineers who are experts in technology but limited

Why this deficiency? Because much of the design is done by engineers who are experts in technology but limited in their understanding of people.

Engineers are trained to think logically. As a result, they come to believe that all people must think this way, and they design their machines accordingly.

We have to accept human behavior the way it is, not the way we would wish it to be.

As I watched people struggle with technology, it became clear that the difficulties were caused by the technology, not the people.

“human error” was the immediate analysis. But the committee I was on discovered that the plant’s control rooms were so poorly designed that error was inevitable: design was at fault, not the operators. The moral was simple: we were designing things for people, so we needed to understand both technology and people.

design presents a fascinating interplay of technology and psychology, that the designers must understand both.

“You are designing for people the way you would like them to be, not for the way they really are.”

ever-increasing complexity of the automobile dashboard, to the increasing automation in the home with its internal networks, complex music, video, and game systems for entertainment and communication, and the increasing automation in the kitchen, everyday life sometimes seems like a never-ending fight against confusion, continued errors, frustration, and a continual cycle of updating and maintaining our belongings.

the rapid rate of technology change outpaces the advances in design. New technologies, new applications, and new methods of interaction are continually arising and evolving.

things are getting better, but as a result, the challenges are ever present.

Designers need to focus their attention on the cases where things go wrong, not just on when things work as planned.

people themselves are often unaware of their true needs, even unaware of

people themselves are often unaware of their true needs, even unaware of the difficulties they are encountering.

Sleep seems to play an important role in strengthening the memories of each day’s experiences.

“Whatever makes you rehearse during sleep is going to determine what you remember later, and conversely, what you’re going to forget,” said Professor Ken Paller of Northwestern University, one of the authors of a recent study on the topic (Oudiette, Antony, Creery, and Paller, 2013).

Human-centered design is a design philosophy. It means starting with a good understanding of people and the needs that the design is intended to meet.

the HCD principle is to avoid specifying the problem as long as possible but instead to iterate upon repeated approximations.

Doing HCD within the rigid time, budget, and other constraints of industry can be a challenge: Chapter 6 examines these issues.

Experience is critical, for it determines how fondly people remember their interactions. Was the overall experience positive, or was it frustrating and confusing? When our home technology behaves in an uninterpretable fashion we can become confused, frustrated, and even angry—all strong negative emotions.

When there is understanding it can lead to a feeling of control, of mastery, and of satisfaction or even pride—all strong positive emotions.

We live in a world filled with objects, many natural, the rest artificial. Every day we encounter thousands of objects, many of them new to us.

Why is it that when we encounter many unusual natural objects, we know how to interact with them? Why is this true with many of the artificial, human-made objects we encounter? The answer lies with a few basic principles. Some of the most important of these principles come from a consideration of affordances. The term affordance refers to the relationship between a physical object and a person (or for that matter, any interacting agent, whether animal or human, or even machines and robots).

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. Most chairs can also be carried by a single person (they afford lifting), but some can only be lifted by a strong person or by a team of people.

Glass affords transparency. At the same time, its physical structure blocks the passage of most physical objects. As a result, glass affords seeing through and support, but not the passage of air or most physical objects (atomic particles can pass through glass). The blockage of passage can be considered an anti-affordance—the prevention of interaction.

To be effective, affordances and anti-affordances have to be discoverable—perceivable. This poses a difficulty with glass. The reason we like glass is its relative invisibility, but this aspect, so useful in the normal window, also hides its anti-affordance property of blocking passage. As a result, birds often try to fly through windows. And every year, numerous people injure themselves when they walk (or run) through closed glass doors or large picture windows.

signaling its presence is required: I call this property a signifier (discussed in the next section).

The notion of affordance and the insights it provides originated with J. J. Gibson, an eminent psychologist who provided many advances to our understanding of human perception.

We disagreed about almost everything. I was an engineer who became a cognitive psychologist, trying to understand how the mind works. He started off as a Gestalt psychologist, but then developed an approach that is today named after him: Gibsonian psychology, an ecological approach to perception.

He argued that the world contained the clues and that people simply picked them up through “direct perception.” I argued that nothing could be direct: the brain had to process the information arriving at the sense organs to put together a coherent interpretation. “Nonsense,” he loudly proclaimed; “it requires no interpretation: it is directly perceived.”

Gibson believed that the combined information picked up by all of our sensory apparatus—sight, sound, smell, touch, balance, kinesthetic, acceleration, body position— determines our perceptions without the need for internal processing or cognition.

the physical objects conveyed important information about how people could interact with them, a property he named “affordance.”

Affordances exist even if they are not visible. For designers, their visibility is critical: visible affordances provide strong clues to the operations of things. A flat plate mounted on a door affords pushing.

Knobs afford turning, pushing, and pulling. Slots are for inserting things into. Balls are for throwing or bouncing. Perceived affordances help people figure out what actions are possible without the need for labels or instructions.

the term became used in ways that had nothing to do with the original.

mention of the term everywhere. Alas,

Many people find affordances difficult to understand because they are relationships, not properties.

They soon discovered that when working with the graphical designs for electronic displays, they needed a way to designate which parts could be touched, slid upward, downward, or sideways, or tapped upon. The actions could be done with a mouse, stylus, or fingers. Some systems responded to body motions, gestures, and spoken words, with no touching of any physical device. How could designers describe what they were doing?

There was no word that fit, so they took the closest existing word—affordance. Soon designers were saying such things as, “I put an affordance there,” to describe why they displayed a circle on a screen to indicate where the person should touch, whether by mouse or by finger.

“that is not an affordance. That is a way of communicating where the touch should be. You are communicating where to do the touching: the affordance of touching exists on the entire screen: you are trying to signify where the touch should take place. That’s not the same thing as saying what action is possible.”

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

1.4.The Sink That Would Not Drain: Where Signifiers Fail. I washed my hands in my hotel sink in London, but then, as shown in Photo A, was left with the question of how to empty the sink of the dirty water. I searched all over for a control: none.

This wall, at the Industrial Design department of KAIST, in Korea, provides an anti-affordance, preventing people from falling down the stair shaft. Its top is flat, an accidental by-product of the design. But flat surfaces afford support, and as soon as one person discovers it can be used to dispose of empty drink containers, the discarded container becomes a signifier,

This wall, at the Industrial Design department of KAIST, in Korea, provides an anti-affordance, preventing people from falling down the stair shaft. Its top is flat, an accidental by-product of the design. But flat surfaces afford support, and as soon as one person discovers it can be used to dispose of empty drink containers, the discarded container becomes a signifier, telling others that it is permissible to discard their items there.

•Affordances are the possible interactions between people and the environment.

Whenever you see hand-lettered signs pasted on doors, switches, or products, trying to explain how to work them, what to do and what not to do, you are also looking at poor design.

A designer approaches his mentor. He is working on a system that recommends restaurants to people, based upon their preferences and those of their friends. But in his tests, he discovered that people never used all of the features. “Why not?” he asks his mentor. (With apologies to Socrates.)

DESIGNER MENTOR I’m frustrated; people aren’t using our application properly. Can you tell me about it?

military tanks that have tracks instead of wheels use separate controls for the speed and direction of each track: to turn right, the left track is increased in speed, while the right track is slowed or even reversed. This is also how a wheelchair is steered.

Natural mapping, by which I mean taking advantage of spatial analogies, leads to immediate understanding. For example, to move an object up, move the control up. To make it easy to determine which control works which light in a large room or auditorium,

Other natural mappings follow from the principles of perception and allow for the natural grouping or patterning of controls and feedback.

In Chapter 3, I discuss how different cultures view time, which has important implications for some kinds of mappings.

Ever drive to a traffic intersection and wait an inordinate amount of time for the signals to change, wondering all the time whether the detection circuits noticed your vehicle (a common problem with bicycles)? What is missing in all these cases is feedback: some way of letting you know that the system is working on your request.

Given the importance of feedback, it is amazing how many products ignore it.

Poor feedback can be worse than no feedback at all, because it is distracting, uninformative, and in many cases irritating and anxiety-provoking.

Too much feedback can be even more annoying than too little. My dishwasher likes to beep at three a.m. to tell me that the wash is done, defeating my goal of having it work in the middle of the night so as not to disturb anyone (and to use less expensive electricity).

Machines that give too much feedback are like backseat drivers. Not only is it distracting to be subjected to continual flashing lights, text announcements, spoken voices, or beeps and boops, but it can be dangerous.

Poor design of feedback can be the result of decisions aimed at reducing costs, even if they make life more difficult for people.

focus upon cost reduction forces the design to use a single light or sound to convey multiple types of information.

Feedback is essential, but it has to be done correctly. Appropriately.

Hospital operating rooms, emergency wards. Nuclear power control plants. Airplane cockpits. All can become confusing, irritating, and life-endangering places because of excessive feedback, excessive alarms, and incompatible message coding.

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

Mental models, as the name implies, are the conceptual models in people’s minds that represent their understanding of how things work.

Consider a pair of scissors: you can see that the number of possible actions is limited. The holes are clearly there to put something into, and the only logical things that will fit are fingers. The holes are both affordances—they allow the fingers to be inserted—and signifiers—they indicate where the fingers are to go.

the buttons have multiple ways of being used. Two of the buttons do different things when pushed quickly or when kept depressed for several seconds.

Conceptual models are valuable in providing understanding, in predicting how things will behave, and in figuring out what to do when things do not go as planned.

A good conceptual model allows us to predict the effects of our actions. Without a good model, we operate by rote, blindly; we do operations as we were told to do them;

When things go wrong, however, or when we come upon a novel situation, then we need a deeper understanding, a good model.

used to own an ordinary, two-compartment refrigerator—nothing very fancy about it. The problem was that I couldn’t set the temperature properly.

Or perhaps our devices won’t have displays, but will quietly whisper the results into our ears,

The devices will be able to do many useful things, but I fear they will also frustrate: so many things to control, so little space for controls or signifiers. The obvious solution is to use exotic gestures or spoken commands, but how will we learn, and then remember, them?

A few decades ago, watches were simple. All you had to do was set the time and keep the watch wound. The standard control was the stem: a knob at the side of the watch. Turning the knob would wind the spring that provided power to the watch movement.

Watches in olden times were expensive instruments, manufactured by hand. They were sold in jewelry stores. Over time, with the introduction of digital technology, the cost of watches decreased rapidly, while their accuracy and reliability increased.

The hard part is to convince people to understand the viewpoints of the others, to abandon their disciplinary viewpoint and to think of the design from the viewpoints of the person who buys the product and those who use it, often different people. The viewpoint of the business is also important,

Interestingly, many people do experience difficulties, but explain them away by blaming themselves.

Most innovation is done as an incremental enhancement of existing products.

“People don’t want to buy a quarter-inch drill.

“People don’t want to buy a quarter-inch drill. They want a quarter-inch hole!”

Why not develop methods that don’t require holes? Or perhaps books that don’t require bookshelves. (Yes, I know: electronic books, e-books.)

Most people can determine the house, but have difficulty answering the question because they can readily imagine the doorknob on both sides of the door. The way to solve this problem is to imagine doing some activity, such as walking up to the front door while carrying heavy packages with both hands: how do you open the door?

Cognition and emotion cannot be separated. Cognitive thoughts lead to emotions: emotions drive cognitive thoughts.

Emotion is highly underrated. In fact, the emotional system is a powerful information processing system that works in tandem with cognition.

Cognition provides understanding: emotion provides value judgments. A human without a working emotional system has difficulty making choices.

Cognition attempts to make sense of the world: emotion assigns value.

Because much human behavior is subconscious—that is, it occurs without conscious awareness—we often don’t know what we are about to do, say, or think until after we have done it. It’s as if we had two minds: the subconscious and the conscious, which don’t always talk to each other.

In calm, nonthreatening situations, the emotional system triggers the release of hormones that relax the muscles and bias the brain toward exploration and creativity. Now the brain is more apt to notice changes in the environment, to be distracted by events, and to piece together events and knowledge that might have seemed unrelated earlier.

A positive emotional state is ideal for creative thought, but it is not very well suited for getting things done.

A positive emotional state is ideal for creative thought, but it is not very well suited for getting things done. Too much, and we call the person scatterbrained, flitting from one topic to another, unable to finish one thought before another comes to mind. A brain in a negative emotional state provides focus: precisely what is needed to maintain attention on a task and finish it. Too much, however, and we get tunnel vision, where people are unable to look

A positive emotional state is ideal for creative thought, but it is not very well suited for getting things done. Too much, and we call the person scatterbrained, flitting from one topic to another, unable to finish one thought before another comes to mind. A brain in a negative emotional state provides focus: precisely what is needed to maintain attention on a task and finish it. Too much, however, and we get tunnel vision, where people are unable to look beyond their narrow point of view.

This has nothing to do with how usable, effective, or understandable the product is. It is all about attraction or repulsion. Great designers use their aesthetic sensibilities to drive these visceral responses. Engineers and other logical people tend to dismiss the visceral response as irrelevant. Engineers are proud of the inherent quality of their work and dismayed when inferior products sell better “just because they look better.”

Reflection is cognitive, deep, and slow. It often occurs after the events have happened.

DESIGN MUST TAKE PLACE AT ALL LEVELS: VISCERAL, BEHAVIORAL, AND REFLECTIVE

THE BEHAVIORAL LEVEL The behavioral level is the home of learned skills, triggered by situations

FIGURE 2.3.Three Levels of Processing: Visceral, Behavioral, and Reflective. Visceral and behavioral levels are subconscious and the home of basic emotions. The reflective level is where conscious thought and decision-making reside, as well as the highest level of emotions.

To the designer, reflection is perhaps the most important of the levels of processing. Reflection is conscious, and the emotions produced at this level are the most protracted: those that assign agency and cause, such as guilt and blame or praise and pride. Reflective responses are part of our memory of events.

Reflective memories are often more important than reality. If we have a strongly positive visceral response but disappointing usability problems at the behavioral level, when we reflect back upon the product, the reflective level might very well weigh the positive response strongly enough to overlook the severe behavioral difficulties (hence the phrase, “Attractive things work better”). Similarly, too much frustration, especially toward the ending stage of use, and our reflections about the experience might overlook the positive visceral qualities.

Vacations are often remembered with fondness, despite the evidence from diaries of repeated discomfort and anguish.

One nasty experience with a service provider can spoil all future experiences. One superb experience can make up for past deficiencies. The behavioral level, which is the home of interaction, is also the home of all expectation-based emotions, of hope and joy, frustration and anger. Understanding arises at a combination of the behavioral and reflective levels. Enjoyment requires all three. Designing at all three levels is so important that I devote an entire book to the topic, Emotional Design. In psychology, there has been a long debate about which happens first: emotion or cognition. Do we run and flee because some

Most products do not cause fear, running, or fleeing, but badly designed devices can induce frustration and anger, a feeling of helplessness and despair, and possibly even hate.

Well-designed devices can induce pride and enjoyment, a feeling of being in control and pleasure—possibly even love and attachment.

Amusement parks are experts at balancing the conflicting responses of the emotional stages, providing rides and fun houses that trigger fear responses from the visceral and behavioral levels, while all the time providing reassurance at the reflective level that the park would never subject anyone to real danger.

expectations. When the results of our actions

One important emotional state is the one that accompanies complete immersion into an activity, a state that the social scientist Mihaly Csikszentmihalyi has labeled “flow.”

When in the flow state, people lose track of time and the outside environment. They are at one with the task they are performing.

The flow state occurs when the challenge of the activity just slightly exceeds our skill level, so full attention is continually required. Flow requires that the activity be neither too easy nor too difficult relative to our level of skill. The constant tension coupled with continual progress and success can be an engaging, immersive experience sometimes lasting for hours.

In the absence of external information, people can let their imagination run free as long as the conceptual models they develop account for the facts as they perceive them.

As a result, people use their thermostats inappropriately, causing themselves unnecessary effort, and often resulting in large temperature swings, thus wasting energy, which is both a needless expense and bad for the environment.

The tendency to repeat an action when the first attempt fails can be disastrous. This has led to numerous deaths when people tried to escape a burning building by attempting to push open exit doors that opened inward, doors that should have been pulled. As a result, in many countries, the law requires doors in public places to open outward, and moreover to be operated by so-called panic bars, so that they automatically open when people, in a panic to escape a fire, push their bodies against them. This is a great application of appropriate affordances: see the door in Figure 2.5.

The presence of a filling hourglass or rotating clock hands is a reassuring sign that work is in progress. When the delay can be predicted, some systems provide time estimates as well as progress bars to indicate how far along the task has gone.

Suppose I try to use an everyday thing, but I can’t. Who is at fault: me or the thing? We are apt to blame ourselves, especially if others are able to use it. Suppose the fault really lies in the device, so that lots of people have the same problems.

LEARNED HELPLESSNESS The phenomenon called learned helplessness might help explain the self-blame. It refers to the situation in which people experience repeated failure at a task. As a result, they decide that the task cannot be done, at least not by them: they are helpless. They stop trying. If this feeling covers a group of tasks, the result can be severe difficulties coping with life. In the extreme case, such learned helplessness leads to depression and to a belief that the individuals cannot cope with everyday life at all.

Sometimes all it takes to get such a feeling of helplessness are a few experiences that accidentally turn out bad. The phenomenon has been most frequently studied as a precursor to the clinical problem of depression, but I have seen it happen after a few bad experiences with everyday objects.

We could call this phenomenon taught helplessness. When people have trouble using technology, especially when they perceive (usually incorrectly) that nobody else is having the same problems, they tend to blame themselves. Worse, the more they have trouble, the more helpless they may feel, believing that they must be technically or mechanically inept. This is just the opposite of the more normal situation where people blame their own difficulties on the environment. This false blame is especially ironic because the culprit here is usually the poor design of the technology, so blaming the environment (the technology) would be completely appropriate.

Consider the normal mathematics curriculum, which continues relentlessly on its way, each new lesson assuming full knowledge and understanding of all that has passed before.

once you fall behind it is hard to catch up. The result: mathematics phobia—not because the material is difficult, but because it is taught so that difficulty in one stage hinders further progress.

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.

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.

We need to remove the word failure from our vocabulary, replacing it instead with learning experience.

With success, sure, we are pleased, but we often have no idea why we succeeded. With failure, it is often possible to figure out why, to ensure that it will never happen again.

One design firm, IDEO, has it as a creed: “Fail often, fail fast,” they say, for they know that each failure teaches them a lot about what to do right.

failures are an essential part of exploration and creativity. If designers and researchers

failures are an essential part of exploration and creativity. If designers and researchers do not sometimes fail, it is a sign that they are not trying hard enough—they are not thinking the great creative thoughts that will provide breakthroughs in how we do things. It is possible to avoid failure, to always be safe. But that is also the route to a dull, uninteresting life.

•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.

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.

how come nobody ever said anything about it? After all, they were encouraged to report all problems with the system. The reason was simple: when the system stopped working or did something strange, they dutifully reported it as a problem. But when they made the Return versus Enter error, they blamed themselves. After all, they had been told what to do. They had simply erred.

Eliminate the term human error. Instead, talk about communication and interaction: what we call an error is usually bad communication or interaction.

Today, we insist that people perform abnormally, to adapt themselves to the peculiar demands of machines, which includes always giving precise, accurate information. Humans are particularly bad at this, yet when they fail to meet the arbitrary, inhuman requirements

Today, we insist that people perform abnormally, to adapt themselves to the peculiar demands of machines, which includes always giving precise, accurate information. Humans are particularly bad at this, yet when they fail to meet the arbitrary, inhuman requirements of machines, we call it human error. No, it is design error. Designers should strive to minimize the chance of inappropriate actions in the first place by using affordances, signifiers, good mapping, and constraints to guide the actions.

People are subjected to continual interruptions. As a result, we are often bouncing back and forth between tasks, having to recover our place, what we were doing, and what we were thinking when we return to a previous task.

machines are programmed to be very fussy about the form of input they require, where the fussiness is not a requirement of the machine but due to the lack of consideration for people in the design of the software. In other words: inappropriate programming. Consider these examples. Many of us spend hours filling out forms on computers—forms that require names, dates, addresses, telephone numbers, monetary sums, and other information in a fixed, rigid format. Worse, often we are not even told the correct format until we get it wrong. Why not figure out the variety of ways a person might fill out a form and accommodate all of them? Some companies have done excellent jobs at this, so let us celebrate their actions. Consider Microsoft’s calendar program. Here, it is possible to specify dates any way you like: “November 23, 2015,” “23 Nov. 15,” or “11.23.15.” It even accepts phrases such as “a week from Thursday,” “tomorrow,” “a week from tomorrow,” or “yesterday.” Same with time. You can enter the time any way you want: “3:45 PM,” “15.35,” “an hour,” “two and one-half hours.” Same with telephone numbers: Want to start with a + sign (to indicate the code for international dialing)? No problem. Like to separate the number fields with spaces, dashes, parentheses, slashes, periods? No problem. As long as the program can decipher the date, time, or telephone number into a legal format, it is accepted. I hope the team that worked on this got bonuses and promotions. Although I single out Microsoft for being the pioneer in accepting a wide variety of formats, it is now becoming standard practice. By the time you read this, I would hope that every program would permit any intelligible format for names, dates, phone numbers, street addresses, and so on, transforming whatever is entered into whatever form the internal programming needs. But I predict that even in the twenty-second century, there will still be forms that require precise accurate (but arbitrary) formats for no reason

seven-stage model of the action cycle can be a valuable design tool, for it provides a basic checklist of questions to ask. In general, each stage of action

seven-stage model of the action cycle can be a valuable design tool, for it provides a basic checklist of questions to ask.

1.What do I want to accomplish? 2.What are the alternative action sequences? 3.What action can I do now? 4.How do I do it? 5.What happened? 6.What does it mean? 7.Is this okay? Have I accomplished my goal? FIGURE 2.7.The Seven Stages of Action as Design Aids. Each of the seven stages indicates a place where the person using the system has a question. The seven

1.Discoverability. It is possible to determine what actions are possible and the current state of the device. 2.Feedback. There is full and continuous information about the results of actions and the current state of the product or service. After an action has been executed, it is easy to determine the new state. 3.Conceptual model. The design projects all the information needed to create a good conceptual model of the system, leading to understanding and a feeling of control. The conceptual model enhances both discoverability and evaluation of results. 4.Affordances. The proper affordances exist to make the desired actions possible. 5.Signifiers. Effective use of signifiers ensures discoverability and that the feedback is well communicated and intelligible. 6.Mappings. The relationship between controls and their actions follows the principles of good mapping, enhanced as much as possible through spatial layout and temporal contiguity. 7.Constraints. Providing physical, logical, semantic, and cultural constraints guides actions and eases interpretation.

Ask yourself how the difficulty came about. Realize that many different groups of people might have been involved, each of which might have had intelligent, sensible reasons for their actions. For example, a troublesome bathroom shower was designed by people who were unable to know how it would be installed, then the shower controls might have been selected by a building contractor to fit the home plans provided by yet another person. Finally, a plumber, who may not have had contact with any of the other people, did the installation. Where did the problems arise? It could have been at any one (or several) of these stages. The result may appear to be poor design, but it may actually arise from poor communication.

One of my self-imposed rules is, “Don’t criticize unless you can do better.” Try to understand how the faulty design might have occurred: try to determine how it could have been done otherwise. Thinking about the causes and possible fixes to bad design should make you better appreciate good design.

next time you come across a well-designed object, one that you can use smoothly and effortlessly on the first try, stop and examine it.

Precise Behavior from Imprecise Knowledge Precise behavior can emerge from imprecise knowledge for four reasons:

1.Knowledge is both in the head and in the world.

2.Great precision is not required. Precision, accuracy, and completeness of knowledge are seldom required. Perfect behavior results if the combined knowledge in the head and in the world is sufficient to distinguish

2.Great precision is not required. Precision, accuracy, and completeness of knowledge are seldom required. Perfect behavior results if the combined knowledge in the head and in the world is sufficient to distinguish an appropriate choice from all others.

so much knowledge is available in the environment, it is surprising how little we need to learn. This is one reason people can function well in their environment and still be unable to describe what they do.

two kinds of knowledge: knowledge of and knowledge how. Knowledge of—what psychologists call declarative knowledge—includes the knowledge of facts and rules. “Stop at red traffic lights.” “New York City is north of Rome.” “China has twice as many people as India.” “To get the key out of the ignition of a Saab car, the gearshift must be in reverse.” Declarative knowledge is easy to write and to teach.

Knowledge how—what psychologists call procedural knowledge—is the knowledge that enables a person to be a skilled musician, to return a serve in tennis, or to move the tongue properly when saying the phrase “frightening witches.” Procedural knowledge is difficult or impossible to write down and difficult to teach.

it is much easier to memorize poetry than to create poems.

I am thinking of three words: one means “a mythical being,” the second is “the name of a building material,” and the third is “a unit of time.” What words do I have in mind?