Design of Everyday Things [3]
Now consider the automobile. The conceptual model is quite different. Yes, the heater and air conditioner also have only two settings, full power or off, but in many autos, the desired temperature is achieved by mixing cold and hot air. In this case, faster results come by turning off the mixing (by setting the temperature control to an extreme) until the desired temperature is reached, then adjusting the mixture to maintain the desired temperature.
The explanations of the home and automobiles are examples of simple conceptual models. They are highly oversimplified but quite adequate for understanding how they work. They make it easy for us to use very different behavior when in the home or in the auto. A good conceptual model can make the difference between successful and erroneous operation of the many devices in our lives.
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. Even the location and operation of the controls require a conceptual model—an obvious and natural relationship between their location and the operation they control so you always know which control does what (in the book, I call this a “natural mapping”). When the designers fail to provide a conceptual model, we will be forced to make up our own, and the ones we make up are apt to be wrong. Conceptual models are critical to good design.
• Feedback. In design, it is important to show the effect of an action. Without feedback, one is always wondering whether anything has happened. Maybe the button wasn’t pushed hard enough; maybe the machine has stopped working; maybe it is doing the wrong thing. Without feedback, we turn equipment off at improper times or restart unnecessarily, losing all our recent work. Or we repeat the command and end up having the operation done twice, often to our detriment. Feedback is critical.
• Constraints. The surest way to make something easy to use, with few errors, is to make it impossible to do otherwise—to constrain the choices. Want to prevent people from inserting batteries or memory cards into their cameras the wrong way, thus possibly harming the electronics? Design them so that they fit only one way, or make it so they work perfectly regardless of how they were inserted.Failure to design with constraints is one reason for all those warnings and attempts to give instructions: all those tiny diagrams on the camera, in obscure locations, often in the same color as the case and unreadable. I look for instructions posted on doors, cameras, and other equipment. 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.
• Affordances. A good designer makes sure that appropriate actions are perceptible and inappropriate ones invisible. DOET introduced the concept of “perceived affordances” to the design community, and to my pleasure, the concept has become immensely popular.
3. The power of observation: If I have been successful, DOET will change the way you see the world. You will never look at a door or light switch the same way again. You will become an acute observer of people, of objects, and of the way they interact. In fact, if there is one single most important part of the book it is this: learn to watch, learn to observe. Observe yourself. Observe others. As the famous baseball player Yogi Berra said, “You can observe a lot by watching.” Problem is, you have to know how to watch. Before DOET, had you seen a hapless user, whether an unknown person or even yourself, you would have been apt to blame the person. Now you will find yourself critiquing the design. Better yet, you will find yourself explaining how to fix the problem.
Design Today
Since The Design of Everyday Things was first