The Design of Everyday Things

In other words, make sure that (1) the user can figure out what to do, and (2) the user can tell what is going on.

If people keep buying poorly designed products, manufacturers and designers will think they are doing the right thing and continue as usual.

Complexity of appearance seems to be determined by the number of controls, whereas difficulty of use is jointly determined by the difficulty of finding the relevant controls (which increases with the number of controls) and difficulty of executing the functions (which may decrease with the number of controls).

The computer has vast potential, more than enough to overcome all its problems. Because it has unlimited power, because it can accept almost any kind of control, and because it can create almost any kind of picture or sound, it has the potential to bridge the gulfs, to make life easier.

Much good design evolves: the design is tested, problem areas are discovered and modified, and then it is continually retested and remodified until time, energy, and resources run out.

real, natural sound is as essential as visual information because sound tells us about things we can’t see, and it does so while our eyes are occupied elsewhere.

When things are visible, they tend to be easier than when they are not. In addition, there must be a close, natural relationship between the control and its function: a natural mapping.

In general, I welcome any technological advance that reduces my need for mental work but still gives me the control and enjoyment of the task. That wayl can exert my mental efforts on the core of the task, the thing to be remembered, the purpose of the arithmetic or the music. I want to use my mental powers for the important things, not fritter them away on the mechanics.

The differences between slips and mistakes are readily apparent in the analysis of the seven stages of action. Form an appropriate goal but mess up in the performance, and you’ve made a slip. Slips are almost always small things: a misplaced action, the wrong thing moved, a desired action undone. Moreover, they are relatively easy to discover by simple observation and monitoring. Form the wrong goal, and you’ve made a mistake. Mistakes can be major events, and they are difficult or even impossible to detect—after all, the action performed is appropriate for the goal.

Because you know that the infor-mation is available in the environment, the information you internally code in memory need be precise enough only to sustain the quality of behavior you desire. This is one reason people can function well in their environment and still be unable to describe what they do.

Many systems are vastly improved by the act of making visible what was invisible before.

The principles that guide a quality, human-centered design are not relevant just to a more pleasurable life—they can save lives.

All the folklore of design has been lost with the brash new engineers who can’t wait to add yet the latest electronic gimmickry to the telephone, whether needed or not.

Design should make use of the natural properties of people and of the world: it should exploit natural relationships and natural constraints. As much as possible, it should operate without instructions or labels. Any necessary instruction or training should be needed only once; with each explanation the person should be able to say, “Of course,” or “Yes, I see.” A simple explanation will suffice if there is reason to the design, if everything has its place and its function, and if the outcomes of actions are visible. If the explanation leads the person to think or say, “How am I going to remember that?” the design has failed.

As each new technology emerges, the companies forget the lessons of the past and let engineers build their fanciful creations, driven by marketing insistence on a proliferation of features. As a result, confusion and distractions increase.

All this brings up an important lesson in design. Once a satisfactory product has been achieved, further change may be counterproductive, especially if the product is successful. You have to know when to stop.

You have to be very careful with sound, however. It easily becomes cute rather than useful. It can annoy and distract as easily as it can aid.

But designers of computer systems seem particularly oblivious to the needs of users, particularly susceptible to all the pitfalls of design. The professional design community is seldom called in to help with computer products. Instead, design is left in the hands of engineers and programmers, people who usually have no experience, and no expertise in designing for people.

Declarative knowledge is easy to write down and to teach. Knowledge how—what psychologists call procedural knowledge—is

mental models, the models people have of themselves, others, the environment, and the things with which they interact. People form mental models through experience, training, and instruction.

We found that to make something easy to use, match the number of controls to the number of functions and organize the panels according to function. To make something look like it is easy, minimize the number of controls. How can these conflicting requirements be met simultaneously? Hide the controls not being used at the moment. By using a panel on which only the relevant controls are visible, you minimize the appearance of complexity. By having a separate control for each function, you minimize complexity of use. It is possible to eat your cake and have it, too.

The example of shoelaces may seem trivial, but it isn’t; like many everyday activities, it is difficult for a large segment of the population and its difficulties can be overcome through the restructuring provided by a simple technology.

Modern designers are subject to many forces that do not allow for the slow, careful crafting of an object over decades and generations.

This short lesson on conceptual models points out that good design is also an act of communication between the designer and the user, except that all the communication has to come about by the appearance of the device itself. The device must explain itself.

We have now encountered the fundamental principles of designing for people: (1) provide a good conceptual model and (2) make things visible.

I call the use of natural signals natural design and elaborate on the approach throughout this book.

Procedural knowledge is largely subconscious.

Procedural knowledge is difficult or impossible to write down and difficult to teach. It is best taught by demonstration and best learned through practice.

Everyday tasks are not difficult because of their inherent complexity. They are difficult only because they require learning arbitrary relationships and arbitrary mappings, and because they sometimes require precision in their execution. The difficulties can be avoided through design that makes obvious what operations are necessary. Good design exploits constraints so that the user feels as if there is only one possible thing to do—the right thing, of course. The designer has to understand and exploit natural constraints of all kinds.

Rule of thumb: when instructions have to be pasted on something (push here, insert this way turn off before doing this), it is badly designed.

The next time you can’t immediately figure out the shower control in a motel or work an unfamiliar television set or stove, remember that the problem is in the design. And the next time you pick up an unfamiliar object and use it smoothly and effortlessly on the first try, stop and examine it: the ease of use did not come about by accident. Someone designed the object carefully and well.

And enjoy yourself. Walk around the world examining the details of design. Take pride in the little things that help; think kindly of the person who so thoughtfully put them in. Realize that even details matter, that the designer may have had to fight to include something helpful. Give mental prizes to those who practice good design: send flowers. Jeer those who don’t: send weeds.

The Design of Everyday Things by Don Norman