The Design of Everyday Things

by Donald A. Norman

When we interact with a product, we need to figure out how to work it. This means discovering what it does, how it works, and what operations are possible: discoverability. 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. It is the conceptual model that provides true understanding. So I now turn to these fundamental principles, starting with affordances, signifiers, mappings, and feedback, then moving to conceptual models. Constraints are covered in Chapters 3 and 4.

Not only did my explanation fail to satisfy the design community, but I myself was unhappy. Eventually I gave up: designers needed a word to describe what they were doing, so they chose affordance. What alternative did they have? I decided to provide a better answer: signifiers. Affordances determine what actions are possible. Signifiers communicate where the action should take place. We need both.

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

All actions need to be confirmed, but in a manner that is unobtrusive.

Designing well is not easy. The manufacturer wants something that can be produced economically. The store wants something that will be attractive to its customers. The purchaser has several demands. In the store, the purchaser focuses on price and appearance, and perhaps on prestige value. At home, the same person will pay more attention to functionality and usability. The repair service cares about maintainability:

There we have it. Seven stages of action:

This is called a root cause analysis: asking “Why?” until the ultimate, fundamental cause of the activity is reached.

Rather than engage in extensive planning and analysis, we go about the day’s activities and do things as opportunities arise.

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

The earlier questions were memory for factual information, what is called declarative memory.

The last question could have been answered factually, but is usually most easily answered by recalling the activities performed to open the door. This is called procedural memory.

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

we use logic and reason after the fact, to justify our decisions to ourselves (to our conscious minds) and to others.

Visceral responses are fast and completely subconscious. They are sensitive only to the current state of things.

Most scientists do not call these emotions: they are precursors to emotion.

Feedback—knowledge of results—is how expectations are resolved and is critical to learning and the development of skilled behavior.

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. Advertisers hope that the strong reflective value associated with a well-known, highly prestigious brand might overwhelm our judgment, despite a frustrating experience in using the product. Vacations are often remembered with fondness, despite the evidence from diaries of repeated discomfort and anguish.

An easy task, far below our skill level, makes it so easy to meet expectations that there is no challenge. Very little or no processing effort is required, which leads to apathy or boredom. A difficult task, far above our skill, leads to so many failed expectations that it causes frustration, anxiety, and helplessness. 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.

FIGURE 2.4. Levels of Processing and the Stages of the Action Cycle. Visceral

We base our models on whatever knowledge we have, real or imaginary, naive or sophisticated.

If you think that the room or oven will cool or heat faster if the thermostat is turned all the way to the maximum setting, you are wrong—you hold an erroneous folk theory of the heating and cooling system. One commonly held folk theory of the working of a thermostat is that it is like a valve: the thermostat controls how much heat (or cold) comes out of the device. Hence, to heat or cool something most quickly, set the thermostat so that the device is on maximum. The theory is reasonable, and there exist devices that operate like this, but neither the heating or cooling equipment for a home nor the heating element of a traditional oven is one of them.

If some unexpected event happens in my home just after I have taken some action, I am apt to conclude that it was caused by that action, even if there really was no relationship between the two. Similarly, if I do something expecting a result and nothing happens, I am apt to interpret this lack of informative feedback as an indication that I didn’t do the action correctly: the most likely thing to do, therefore, is to repeat the action, only with more force.

Some studies show it is wise to underpredict—that is, to say an operation will take longer than it actually will. When the system computes the amount of time, it can compute the range of possible times. In that case it ought to display the range, or if only a single value is desirable, show the slowest, longest value. That way, the expectations are liable to be exceeded, leading to a happy result.

Everyone sometimes acts in a way that seems strange, bizarre, or simply wrong and inappropriate. When we do this, we tend to attribute our behavior to the environment. When we see others do it, we tend to attribute it to their personalities.

We need to remove the word failure from our vocabulary, replacing it instead with learning experience. To fail is to learn: we learn more from our failures than from our successes. 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.

to the designers who are reading this, let me give some advice:

The information that helps answer questions of execution (doing) is feedforward. The information that aids in understanding what has happened is feedback.

The insights from the seven stages of action lead us to seven fundamental principles of design:

knowledge of and knowledge how. Knowledge of—what psychologists call declarative knowledge—includes the knowledge of facts and rules.

People may know many things: that doesn’t mean they are true.

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

Look around you at the variety of ways people arrange their rooms and desks. Many styles of organization are possible, but invariably the physical layout and visibility of the items convey information about relative importance.

Suppose I keep all my notes in a small red notebook. If this is my only notebook, I can describe it simply as “my notebook.” If I buy several more notebooks, the earlier description will no longer work.

Consider the constraints of rhyming. If you wish to rhyme one word with another, there are usually a lot of alternatives. But if you must have a word with a particular meaning to rhyme with another, the joint constraints of meaning and rhyme can cause a dramatic reduction in the number of possible candidates, sometimes reducing a large set to a single choice.

Psychologists distinguish between two major classes of memory: short-term or working memory, and long-term memory.

The full table and the mnemonics for learning the pairings are readily found on the Internet by searching for “number-consonant mnemonic.”

I suspect that STM holds something akin to a pointer to an already encoded item in long-term memory, which means the memory capacity is the number of pointers it can keep. This would account for the fact that the length or complexity of the item has little impact—simply the number of items.

Driving is primarily visual, so the use of auditory and haptic modalities minimizes interference with the visual task.

“Memories in our brain are changing all of the time. Sometimes you improve memory storage by rehearsing all the details, so maybe later you remember better—or maybe worse if you’ve embellished too much.”

The way by which people retrieve the needed knowledge is still unknown, but probably involves some form of pattern-matching mechanism coupled with a confirmatory process that checks for consistency with the required knowledge.

The most effective way of helping people remember is to make it unnecessary.

true

Well-learned skills bypass the need for conscious oversight and control: conscious control is only required for initial learning and for dealing with unexpected situations.

Civilization advances by extending the number of important operations which we can perform without thinking about them.

Science deals in truth, practice deals with approximations. Practitioners don’t need truth: they need results relatively quickly that, although inaccurate, are “good enough” for the purpose to which they will be applied.

There are many strategies for reminding. One is simply to keep the knowledge in your head, trusting yourself to recall it at the critical time. If the event is important enough, you will have no problem remembering it. It would be quite strange to have to set a calendar alert to remind yourself, “Getting married at 3 PM.”

As we move away from many physical aids, such as printed books and magazines, paper notes, and calendars, much of what we use today as knowledge in the world will become invisible. Yes, it will all be available on display screens, but unless the screens always show this material, we will have added to the burden of memory in the head. We may not have to remember all the details of the information stored away for us, but we will have to remember that it is there, that it needs to be redisplayed at the appropriate time for use or for reminding.

“transactive memory.”

“cybermind,”

• Best mapping: Controls are mounted directly on the item to be controlled.

• Second-best mapping: Controls are as close as possible to the object to be controlled. • Third-best mapping: Controls are arranged in the same spatial configuration as the objects to be controlled.