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When there are major emergencies, then even important signals have to be prioritized. When every device is signaling a major emergency, nothing is gained by the resulting cacophony. The continual beeps and alarms of equipment can be dangerous. In many emergencies, workers have to spend valuable time turning off all the alarms because the sounds interfere with the concentration required to solve the problem. Hospital operating rooms, emergency wards. Nuclear power control plants. Airplane cockpits. All can become confusing, irritating, and life-endangering places because of excessive feedback,
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CONCEPTUAL MODELS A conceptual model is an explanation, usually highly simplified, of how something works.
In fact, there are no folders inside the computer—those are effective conceptualizations designed to make them easier to use. Sometimes
Mental models, as the name implies, are the conceptual models in people’s minds that represent their understanding of how things work.
The holes are both affordances—they allow the fingers to be inserted—and signifiers—they indicate where the fingers are to go.
The only way to tell how to work the watch is to read the manual, over and over again. With the scissors, moving the handle makes the blades move. The watch provides no visible relationship between the buttons and the possible actions, no discernible relationship between the actions and the end results. I really like the watch: too bad I can’t remember all the functions.
It was extremely difficult to regulate the temperature of my old refrigerator. Why? Because the controls suggest a false conceptual model. Two compartments, two controls, which implies that each control is responsible for the temperature of the compartment that carries its name: this conceptual model is shown in Figure 1.10A. It is wrong. In fact, there is only one thermostat and only one cooling mechanism.
One control adjusts the thermostat setting, the other the relative proportion of cold air sent to each of the two compartments of the refrigerator. This is why the two controls interact: this conceptual model is shown in Figure 1.10B. In addition, there must
a temperature sensor, but there is no way of knowing where it is located. With the conceptual model suggested by the controls, adjusting the temperatures is almost impossible and always frustrating...
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Why did the manufacturer suggest the wrong conceptual model? We will never know. In the twenty-five years since the publication of the first edition of this book, I have had many letters from people thanking me for explaining their confusing refrigerator, b...
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But far less expensive solutions are possible. With today’s inexpensive sensors and motors, it should be possible to have a single cooling unit with a motor-controlled valve controlling the relative proportion of cold air diverted to each compartment. A simple, inexpensive computer chip could regulate the cooling unit and valve position so that the temperatures in the two compartments match their targets. A bit more work for the engineering design team? Yes, but the results would be worth
The System Image
things.” No, she had it backward. It is the mechanical thing that should be apologizing, perhaps saying, “I’m sorry. I am so bad with people.”
But she also had a second problem: she thought the problem lay in her own lack of ability: she blamed herself, falsely.
So I resorted to the most powerful tool employed by experts the world around—I banged on the cabinet. And yes, it opened. In my mind,
decided (without any evidence) that my hit had jarred the mechanism sufficiently to allow the drawer to open.
When people use something, they face two
gulfs: the Gulf of Execution, where they try to figure out how it operates, and the Gulf of Evaluation, where they try to figure out what happened (Figure 2.1). The role of the designer is to help people bridge the two gulfs.
In the case of the filing cabinet, there were visible elements that helped bridge the Gulf of Execution when everything was working perfectly. The drawer handle clearly signified that it should be pulled and the slider on the handle indicated how to release the catch that normally held the drawer in place. But when these operations fail...
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The Gulf of Evaluation reflects the amount of effort that the person must make
to interpret the physical state of the device and to determine how well the expectations and intentions have been met.
they simply give up, deciding that they are incapable of understanding them. Both explanations are wrong.
We bridge the Gulf of Execution through the use of signifiers, constraints, mappings, and a conceptual model.
We bridge the Gulf of Evaluation through the use of feedback and a conceptual model.
There are two parts to an action: executing
the action and then evaluating the results: doing and interpreting.
The seven stages provide a guideline for developing new products or services.
“People don’t want to buy a quarter-inch drill. They want a quarter-inch hole!” Levitt’s example of the drill implying that the goal is really a hole is only partially correct, however. When people go to a store to buy a drill, that is not their real goal. But why would anyone want a quarter-inch hole? Clearly that is an intermediate goal. Perhaps they wanted to hang shelves on the wall. Levitt stopped too soon.
Once you realize that they don’t really want the drill, you realize that perhaps they don’t really want the hole, either: they want to install their bookshelves. Why not develop methods that don’t require holes? Or perhaps books that don’t require bookshelves. (Yes, I know: electronic books, e-books.)
The most basic level of processing is called visceral. This is sometimes referred to as “the lizard brain.” All people have the same basic visceral responses. These are part of the basic protective mechanisms of the human affective system, making quick judgments
about the environment: good or bad, safe or dangerous.
minimizes its ability to learn.
For designers, the most critical aspect of the behavioral level is that every action is associated with an expectation.
DESIGN MUST TAKE PLACE AT ALL LEVELS: VISCERAL, BEHAVIORAL, AND REFLECTIVE
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”).
Vacations are often remembered with fondness, despite the evidence from diaries of repeated discomfort and anguish.
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 event happened tha...
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The three-level analysis shows that both of these ideas can be co...
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emotion comes first. An unexpected loud noise can cause automatic visceral and behavioral responses that make us flee. Then, the reflective system observes itself fleeing and deduces that it is afraid. The actions of running an...
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But sometimes cognition occurs first. Suppose the street where we are walking leads to a dark and narrow section. Our reflective system might conjure numerous imagined threats that await us. At some point, the imagined depiction of potential harm is large enough to trigger the behavioral system, causing us to ...
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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.
Mihaly Csikszentmihalyi has labeled “flow.” Csikszentmihalyi has long studied how people interact with their work and play, and how their lives reflect this intermix of activities. 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 task, moreover, is at just the proper level of difficulty: difficult enough to provide a challenge and require continued attention, but not so difficult that it invokes frustration and anxiety.
If you are in a cold room, in a hurry to get warm, will the room heat more quickly if you turn the thermostat to its maximum setting? Or if you want the oven to reach its working temperature faster, should you turn the temperature dial all the way to maximum, then turn it down once the desired temperature is reached? Or to cool a room most quickly, should you set the air conditioner thermostat
to its lowest temperature setting?
People try to find causes for events. They tend to assign a causal relation whenever two things occur in succession.
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.
This is a great application of appropriate affordances: see the door in Figure 2.5.
