全书摘抄
2015-05-28
Design of Everyday Things (Norman, Don)
- 您在位置 #129-140的标注 | 添加于 2014年10月10日星期五 下午1:26:57
Consider the thermostat. When some people enter a cold house, they turn the thermostat to a very high temperature in order to reach the desired level more quickly. They do this because of their internal mental model of how the furnace works. The model is sensible and coherent, even if not well thought out. It is also wrong. But how would they know? Although this behavior is wrong for the home, it works for most automobiles—turn the heat or air conditioning up all the way, and when the interior is at the correct temperature, adjust the temperature control again. To understand how to use things, we need conceptual models of how they work. Home furnaces, air conditioners, and even most household ovens have only two levels of operation: full power or off. Therefore, they are always heating or cooling to the desired temperature as rapidly as possible. In these cases, setting the thermostat too high does nothing but waste energy when the temperature overshoots the target. 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.
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Design of Everyday Things (Norman, Don)
- 您在位置 #465-466的标注 | 添加于 2014年10月13日星期一 下午2:13:45
Something that happens right after an action appears to be caused by that action.
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Design of Everyday Things (Norman, Don)
- 您在位置 #468-469的标注 | 添加于 2014年10月13日星期一 下午2:15:14
When an action has no apparent result, you may conclude that the action was ineffective. So you repeat it.
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Design of Everyday Things (Norman, Don)
- 您在位置 #485-487的标注 | 添加于 2014年10月13日星期一 下午2:21:36
Irving Biederman, a psychologist who studies visual perception, estimates that there are probably “30,000 readily discriminable objects for the adult.”5
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Design of Everyday Things (Norman, Don)
- 您在位置 #519-522的标注 | 添加于 2014年10月13日星期一 下午2:30:09
For everyday things, conceptual models need not be very complex. After all, scissors, pens, and light switches are pretty simple devices. There is no need to understand the underlying physics or chemistry of each device we own, simply the relationship between the controls and the outcomes. When the model presented to us is inadequate or wrong (or, worse, nonexistent), we can have difficulties.
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Design of Everyday Things (Norman, Don)
- 您在位置 #546-550的标注 | 添加于 2014年10月13日星期一 下午2:37:55
The design model is the designer’s conceptual model. The user’s model is the mental model developed through interaction with the system. The system image results from the physical structure that has been built (including documentation, instructions, and labels). The designer expects the user’s model to be identical to the design model. But the designer doesn’t talk directly with the user—all communication takes place through the system image. If the system image does not make the design model clear and consistent, then the user will end up with the wrong mental model.
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Design of Everyday Things (Norman, Don)
- 您在位置 #623-625的标注 | 添加于 2014年10月13日星期一 下午11:52:30
The “R” button is kind of a vestigial feature. It is very hard to remove features of a newly designed product that had existed in an earlier version. It’s kind of like physical evolution. If a feature is in the genome, and if that feature is not associated with any negativity (i.e., no customers gripe about it), then the feature hangs on for generations.
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Design of Everyday Things (Norman, Don)
- 您在位置 #646-651的标注 | 添加于 2014年10月14日星期二 上午12:02:36
Whenever the number of possible actions exceeds the number of controls, there is apt to be difficulty. The telephone system has twenty-four functions, yet only fifteen controls—none of them labeled for specific action. In contrast, the trip computer for the car performs seventeen functions with fourteen controls. With minor exceptions, there is one control for each function. In fact, the controls with more than one function are indeed harder to remember and use. When the number of controls equals the number of functions, each control can be specialized, each can be labeled. The possible functions are visible, for each corresponds with a control. If the user forgets the functions, the controls serve as reminders.
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Design of Everyday Things (Norman, Don)
- 您在位置 #654-656的标注 | 添加于 2014年10月14日星期二 上午12:03:31
Visibility acts as a good reminder of what can be done and allows the control to specify how the action is to be performed. The good relationship between the placement of the control and what it does makes it easy to find the appropriate control for a task. As a result, there is little to remember.
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Design of Everyday Things (Norman, Don)
- 您在位置 #776-777的标注 | 添加于 2014年10月14日星期二 下午2:29:57
The development of a technology tends to follow a U-shaped curve of complexity: starting high; dropping to a low, comfortable level; then climbing again.
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Design of Everyday Things (Norman, Don)
- 您在位置 #777-779的标注 | 添加于 2014年10月14日星期二 下午2:31:18
New kinds of devices are complex and difficult to use. As technicians become more competent and an industry matures, devices become simpler, more reliable, and more powerful. But then, after the industry has stabilized, newcomers figure out how to add increased power and capability, but always at the expense of added complexity and sometimes decreased reliability.
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Design of Everyday Things (Norman, Don)
- 您在位置 #862-865的标注 | 添加于 2014年10月15日星期三 上午7:29:49
If an error is possible, someone will make it. The designer must assume that all possible errors will occur and design so as to minimize the chance of the error in the first place, or its effects once it gets made. Errors should be easy to detect, they should have minimal consequences, and, if possible, their effects should be reversible.
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Design of Everyday Things (Norman, Don)
- 您在位置 #877-879的标注 | 添加于 2014年10月15日星期三 上午7:36:16
Of course, Newton and his successors assume the absence of friction and air. Aristotle lived in a world where there was always friction and air resistance. Once friction is involved, then objects in motion tend to stop unless you keep pushing. Aristotle’s theory may be bad physics, but it describes reasonably well what we can see in the real world.
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Design of Everyday Things (Norman, Don)
- 您在位置 #950-958的标注 | 添加于 2014年10月18日星期六 下午1:51:29
One major aspect of the assignment of blame is that we frequently have little information on which to make the judgment, and what little we have may be wrong. As a result, blame or credit can be assessed almost independently of reality. Here is where the apparent simplicity of everyday objects causes problems. Suppose I try to use an everyday thing, but I can’t: Where is the fault, in my action or in the thing? We are apt to blame ourselves. If we believe that others are able to use the device and if we believe that it is not very complex, then we conclude that any difficulties must be our own fault. Suppose the fault really lies in the device, so that lots of people have the same problems. Because everyone perceives the fault to be his or her own, nobody wants to admit to having trouble. This creates a conspiracy of silence, maintaining the feelings of guilt and helplessness among users. Interestingly enough, the common tendency to blame ourselves for failures with everyday objects goes against the normal attributions people make. In general, it has been found that people attribute their own problems to the environment, those of other people to their personalities.
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Design of Everyday Things (Norman, Don)
- 您在位置 #972-974的标注 | 添加于 2014年10月18日星期六 下午1:55:49
It seems natural for people to blame their own misfortunes on the environment. It seems equally natural to blame other people’s misfortunes on their personalities. Just the opposite attribution, by the way, is made when things go well.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1057-1065的标注 | 添加于 2014年10月25日星期六 下午1:50:39
To get something done, you have to start with some notion of what is wanted—the goal that is to be achieved. Then, you have to do something to the world, that is, take action to move yourself or manipulate someone or something. Finally, you check to see that your goal was made. So there are four different things to consider: the goal, what is done to the world, the world itself, and the check of the world. The action itself has two major aspects: doing something and checking. Call these execution and evaluation (figure 2.2). Real tasks are not quite so simple. The original goal may be imprecisely specified—perhaps “get something to eat,” “get to work,” “get dressed,” “watch television.” Goals do not state precisely what to do—where and how to move, what to pick up. To lead to actions goals must be transformed into specific statements of what is to be done, statements that I call intentions. A goal is something to be achieved, often vaguely stated. An intention is a specific action taken to get to the goal. Yet even intentions are not specific enough to control actions.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1088-1093的标注 | 添加于 2014年10月25日星期六 下午1:59:31
Seven stages of action: one for goals, three for execution, and three for evaluation. • Forming the goal • Forming the intention • Specifying an action • Executing the action • Perceiving the state of the world • Interpreting the state of the world • Evaluating the outcome
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Design of Everyday Things (Norman, Don)
- 您在位置 #1187-1198的标注 | 添加于 2014年11月9日星期日 上午10:14:30
Precise behavior can emerge from imprecise knowledge for four reasons. 1. Information is in the world. Much of the information a person needs to do a task can reside in the world. Behavior is determined by combining the information in memory (in the head) with that in the world. 2. Great precision is not required. Precision, accuracy, and completeness of knowledge are seldom required. Perfect behavior will result if the knowledge describes the information or behavior sufficiently to distinguish the correct choice from all others. 3. Natural constraints are present. The world restricts the allowed behavior. The physical properties of objects constrain possible operations: the order in which parts can go together and the ways in which an object can be moved, picked up, or otherwise manipulated. Each object has physical features—projections, depressions, screwthreads, appendages—that limit its relationships to other objects, operations that can be performed to it, what can be attached to it, and so on. 4. Cultural constraints are present. In addition to natural, physical constraints, society has evolved numerous artificial conventions that govern acceptable social behavior. These cultural conventions have to be learned, but once learned they apply to a wide variety of circumstances.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1197 的笔记 | 添加于 2014年11月9日星期日 上午10:15:33
interface between human and world
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Design of Everyday Things (Norman, Don)
- 您在位置 #1197 的笔记 | 添加于 2014年11月9日星期日 上午10:17:13
interface between human and world
dance with shackles on
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Design of Everyday Things (Norman, Don)
- 您在位置 #1211-1212的标注 | 添加于 2014年11月9日星期日 上午10:24:21
Whenever information needed to do a task is readily available in the world, the need for us to learn it diminishes.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1231 的笔记 | 添加于 2014年11月9日星期日 上午10:43:28
to compare horizontally and only to find the differences
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Design of Everyday Things (Norman, Don)
- 您在位置 #1230-1231的标注 | 添加于 2014年11月9日星期日 上午10:43:29
in normal life, we have to distinguish between the penny and other U.S. coins, not between several versions of one denomination.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1232-1239的标注 | 添加于 2014年11月9日星期日 上午10:44:52
People function through their use of 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 lights.” “New York City lies on a parallel a bit south of Madrid, San Diego’s longitude is east of Reno.” “To get the key out of the ignition, the car must be in reverse.” Declarative knowledge is easy to write down and to teach. Knowledge how—what psychologists call procedural knowledge—is the knowledge that enables a person to perform music, to stop a car smoothly with a flat tire on an icy road, 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 best taught by demonstration and best learned through practice. Even the best teachers cannot usually describe what they are doing. Procedural knowledge is largely subconscious.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1243-1244的标注 | 添加于 2014年11月9日星期日 上午10:46:41
We place items in specific locations as reminders. In general, people structure the environment to provide a considerable amount of the information required for something to be remembered.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1534-1539的标注 | 添加于 2015年1月1日星期四 上午10:29:31
A good reminding method is to put the burden on the thing itself. Do my neighbors want me to take them to the airport? Fine, but they have to call me up the night before and remind me. Do I want to remember to take a book to the university to give to a colleague? I put the book someplace where I cannot fail to see it when I leave the house. A good spot is against the front door of the house. I can’t leave without tripping over the book. If I am at a friend’s house and I borrow a paper or a book, I remember to take it by putting my car keys on it. Then when I leave, I am reminded. Even if I forget and go out to my car, I can’t drive away without the keys.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1544-1545的标注 | 添加于 2015年1月1日星期四 上午10:29:40
The ideal reminder has to have both components: the signal that something is to be remembered, the message of what it is.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1595-1597的标注 | 添加于 2015年1月1日星期四 上午10:34:58
If a design depends upon labels, it may be faulty. Labels are important and often necessary, but the appropriate use of natural mappings can minimize the need for them. Wherever labels seem necessary, consider another design.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1616-1618的标注 | 添加于 2015年1月1日星期四 上午10:40:03
Knowledge (or information) in the world and in the head are both essential in our daily functioning. But to some extent we can choose to lean more heavily on one or the other. That choice requires a trade off—gaining the advantages of knowledge in the world means losing the advantages of knowledge in the head (figure 3.6).
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Design of Everyday Things (Norman, Don)
- 您在位置 #1579-1579的标注 | 添加于 2015年1月1日星期四 上午10:40:32
We can see that the number of possible sequences has been reduced from twenty-four to one.16
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Design of Everyday Things (Norman, Don)
- 您在位置 #1618 的笔记 | 添加于 2015年1月1日星期四 上午10:46:30
brain and external tools like evernote
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Design of Everyday Things (Norman, Don)
- 您在位置 #1634-1636的标注 | 添加于 2015年1月1日星期四 上午10:48:30
Knowledge in the world is easier to learn, but often more difficult to use. And it relies heavily upon the continued physical presence of the information; change the environment and the information is changed. Performance relies upon the physical presence of the task environment.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1635 的笔记 | 添加于 2015年1月1日星期四 上午10:50:54
ui and user guide, a serie of continuous interactions
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Design of Everyday Things (Norman, Don)
- 您在位置 #1667-1667的标注 | 添加于 2015年1月1日星期四 上午11:09:27
Affordances suggest the range of possibilities, constraints limit the number of alternatives.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1942-1944的标注 | 添加于 2015年2月15日星期日 下午5:46:43
It does not take much examination to discover the reason for the difficulties: there is no visual feedback. As a result, users (1) have trouble remembering their place in the lengthy sequence of required steps; (2) have trouble remembering what next needs to be done; and (3) cannot easily check the information just entered to see if it is what was intended, and then cannot easily change it, if they decide it is wrong.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1989-1990的标注 | 添加于 2015年2月15日星期日 下午6:03:07
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.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1988-1994的标注 | 添加于 2015年2月15日星期日 下午6:05:01
Bill Gaver, who has been studying use of sound in my laboratory, points out that 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. Natural sounds reflect the complex interaction of natural objects: the way one part moves against another; the material of which the parts are made—hollow or solid, metal or wood, soft or hard, rough or smooth. Sounds are generated when materials interact, and the sound tells us whether they are hitting, sliding, breaking, tearing, crumbling, or bouncing. Moreover, sounds differ according to the characteristics of the objects, according to their size, solidity, mass, tension, and material. And they differ with how fast things are going and how far away from us they are.
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Design of Everyday Things (Norman, Don)
- 您在位置 #1999-2003的标注 | 添加于 2015年2月15日星期日 下午6:07:12
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. One of the virtues of sounds is that they can be detected even when attention is applied elsewhere. But this virtue is also a deficit, for sounds are often intrusive. Sounds are difficult to keep private unless the intensity is low or earphones are used. This means both that neighbors may be annoyed and that others can monitor your activities. The use of sound to convey information is a powerful and important idea, but still in its infancy.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2031-2035的标注 | 添加于 2015年2月15日星期日 下午6:20:29
Errors come in several forms. Two fundamental categories are slips and mistakes. Slips result from automatic behavior, when subconscious actions that are intended to satisfy our goals get waylaid en route. Mistakes result from conscious deliberations. The same processes that make us creative and insightful by allowing us to see relationships between apparently unrelated things, that let us leap to correct conclusions on the basis of partial or even faulty evidence, also lead to error.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2038-2042的标注 | 添加于 2015年2月15日星期日 下午6:21:35
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.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2049-2053的标注 | 添加于 2015年2月15日星期日 下午6:27:16
Slips show up most frequently in skilled behavior. We don’t make so many slips in things we are still learning. In part, slips result from a lack of attention. On the whole, people can consciously attend to only one primary thing at a time. But we often do many things at once. We walk while we talk; we drive cars while we talk, sing, listen to the radio, use a telephone, take notes, or read a map. We can do more than one thing at a time only if most of the actions are done automatically, subconsciously, with little or no need for conscious attention.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2060-2061的标注 | 添加于 2015年2月15日星期日 下午6:28:55
We can place slips into one of six categories: capture errors, description errors, data-driven errors, associative activation errors, loss-of-activation errors, and mode errors.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2070-2072的标注 | 添加于 2015年2月15日星期日 下午6:33:29
The capture error appears whenever two different action sequences have their initial stages in common, with one sequence being unfamiliar and the other being well practiced. Seldom, if ever, does the unfamiliar sequence capture the familiar one.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2076-2085的标注 | 添加于 2015年2月15日星期日 下午6:37:01
In the common slip known as the description error, the intended action has much in common with others that are possible. As a result, unless the action sequence is completely and precisely specified, the intended action might fit several possibilities. Suppose that my tired student in the example formed a mental description of his intended action something like “throw the shirt into the opening at the top of the container.” This description would be perfectly unambiguous and sufficient were the laundry basket the only open container in sight; but when the open toilet was visible, its characteristics matched the description and triggered the inappropriate action. This is a description error because the internal description of the intention was not sufficiently precise. Description errors usually result in performing the correct action on the wrong object. Obviously, the more the wrong and right objects have in common, the more likely the errors are to occur. Description errors, like all slips, are more likely when we are distracted, bored, involved in other activities, under extra stress, or otherwise not inclined to pay full attention to the task at hand. Description errors occur most frequently when the wrong and right objects are physically near each other. People have reported a number of description errors to me.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2124-2129的标注 | 添加于 2015年2月15日星期日 下午6:49:30
Mode errors occur when devices have different modes of operation, and the action appropriate for one mode has different meanings in other modes. Mode errors are inevitable any time equipment is designed to have more possible actions than it has controls or displays, so the controls must do double duty. Mode errors are especially likely where the equipment does not make the mode visible, so the user is expected to remember what mode has been established, sometimes for many hours. Mode errors are common with digital watches and computer systems (especially text editors). Several accidents in commercial aviation can be attributed to mode errors, especially in the use of the automatic pilots (which have a large number of complex modes).
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Design of Everyday Things (Norman, Don)
- 您在位置 #2144-2156的标注 | 添加于 2015年2月15日星期日 下午7:11:13
Suppose I were driving my car to the bank. At any given moment, the action being performed could be described at many different levels: • Driving to the bank • Turning into the parking lot • Making a right turn • Rotating the steering wheel clockwise • Moving my left hand upward and to the right and my right hand downward • Increasing the tension on the sternocostal portion of the pectoralis major muscle All these levels are active at the same time. The most global description (the one at the top of the list), is called the high-level specification. The more detailed descriptions, the ones at the bottom of the list, are called the low-level specifications. Any one of them might be in error. It is often possible to detect that the result of an action is not as planned, but then not to know at which level of specification the error has taken place. Problems of level commonly thwart the correction of error. My collection of slips includes several examples in which a person detects a problem but attempts to correct it at the wrong level.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2157-2161的标注 | 添加于 2015年2月15日星期日 下午7:12:16
One frequent example is the nonworking key, reported to me both for cars and homes. Someone goes to his or her car and the key won’t work. The first response is to try again, perhaps holding the key more level or straight. Then the key is reversed, tried upside down. When that fails, the key is examined and perhaps another tried in its stead. Then the door is wiggled, shaken, hit. Finally, the person decides that the lock has broken, and walks around the car to try the other door, at which point it is suddenly clear that this is the wrong car.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2204-2204的标注 | 添加于 2015年2月15日星期日 下午7:21:07
When you build an error-tolerant mechanism, people come to rely upon it, so it had better be reliable.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2227-2239的标注 | 添加于 2015年2月20日星期五 下午10:35:10
Another theory is based on the filing cabinet model, wherein there are lots of cross references and pointers to other records. This theory has a good deal going for it, and it is probably a reasonable characterization of the most prominent approach today. Of course, it is not called a file cabinet theory. It goes by the names of “schema theory,” “frame theory,” or sometimes “semantic networks” and “propositional encoding.” The individual file folders are defined in the formal structure of the schemas or frames, and the connections and associations among the individual records make the structure into a vast and complex network. The essence of the theory consists of three beliefs, all reasonable and supported by considerable evidence: (1) that there is logic and order to the individual structures (this is what the schema or frame is about); (2) that human memory is associative, with each schema pointing and referring to multiple others to which it is related or that help define the components (thus the term “network”); and (3) that much of our power for deductive thought comes from using the information in one schema to deduce the properties of another (thus the term “propositional encoding”). 6 To illustrate the third concept: once I learn that all living animals breathe, I know that any live animal I will ever meet will breathe. I don’t have to learn this separately for all animals. We call this the “default value.” Unless told otherwise, anything I learn for a general concept applies to all of its instances by default. Default values do not have to apply to everything—I can learn exceptions, such as that all birds fly except for penguins and ostriches. But defaults hold true unless an exception shows otherwise. Deduction is a most useful and powerful property of human memory.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2282-2294的标注 | 添加于 2015年3月9日星期一 下午10:37:32
Consider what happens when two similar events are experienced: they merge together to form a kind of average, a “prototypical event.” This prototype governs interpretations and actions related to any other event that seems similar. What happens when something really discrepant occurs? If it is quite different from the prototype, it still manages to maintain its identity when thrown into memory. It stands out by itself. If there were a thousand similar events, we would tend to remember them as one composite prototype. If there were just one discrepant event, we would remember it, too, for by being discrepant it didn’t get smudged up with the rest. But the resulting memory is almost as if there had been only two events: the common one and the discrepant one. The common one is a thousand times more likely, but not to the memory; in memory there are two things, and the discrepant event hardly seems less likely than the everyday one. So it is with human memory. We mush together details of things that are similar, and give undue weight to the discrepant. We relish discrepant and unusual memories. We remember them, talk about them, and bias behavior toward them in wholly inappropriate ways. What has this to do with everyday thought? A lot. Everyday thought seems to be based upon past experiences, upon our ability to retrieve an event from the past and use it to model the present. This event-based reasoning is powerful, yet fundamentally flawed. Because thought is based on what can be recalled, the rare event can predominate.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2327-2337的标注 | 添加于 2015年3月10日星期二 下午1:43:54
SHALLOW STRUCTURES The menu of an ice cream store provides a good example of a shallow structure (figure 5.2). There are many alternative actions, but each is simple; there are few decisions to make after the single top-level choice. The major problem is to decide which action to do. Difficulties arise from competing alternatives, not from any prolonged search, problem solving, or trial and error. In shallow structures, there’s no problem of planning or depth of analysis. NARROW STRUCTURES A cookbook recipe is a good example of a narrow structure (figure 5.3). A narrow structure arises when there are only a small number of alternatives, perhaps one or two. If each possibility leads to only one or two further choices, then the resulting tree structure can be said to be narrow and deep. Just as the ice cream store menu is an example of a shallow structure, the multicourse, fixed menu meal can serve as an example of a deep structure. Although there may be many courses, for each course the diner is either automatically served the relevant dish or offered the choice of one or two dishes. The only action required is to accept one or to refuse: no deep thought is required.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2467-2474的标注 | 添加于 2015年3月10日星期二 下午2:23:41
The contrast in our understanding before and after an event can be dramatic. The psychologist Baruch Fischhoff has studied explanations given in hindsight, where events seem completely obvious and predictable after the fact but completely unpredictable beforehand.13 Fischhoff presented people with a number of situations and asked them to predict what would happen: they were correct only at the chance level. He then presented the same situation along with the actual outcome to another group of people, asking them to state how likely the outcome was: when the actual outcome was known, it appeared to be plausible and likely, whereas the others appeared unlikely. When the actual outcome was not known, the various alternatives had quite different plausibility. It is a lot easier to determine what is obvious after it has happened.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2554-2555的标注 | 添加于 2015年3月10日星期二 下午2:53:51
It is important to think through the implications of that cost—to decide whether people will deliberately disable the forcing function.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2555-2567的标注 | 添加于 2015年3月10日星期二 下午2:56:08
The history of seatbelts in autos provides a good example. Despite all the evidence that seatbelts are an effective means of saving lives, some people dislike them enough that they refuse to wear them, probably because the perceived risk is so much less than the actual, statistical risk. For a short period, the United States tried a forcing function on seatbelts: a special interlock was installed on each new car. If the driver’s and passengers’ belts were not fastened, the car would not start (and a buzzer would sound). This forcing function was so disliked that most drivers had their mechanics disconnect it. The law was quickly changed. There seemed to be three problems. First, many people did not want to wear seatbelts, and they resented the mechanical forcing function. Second, the forcing function couldn’t distinguish legitimate cases in which the seatbelt should not be buckled from illegitimate ones. Thus, if you wanted to carry a package in the passenger’s seat, the weightsensing element in the seat registered a person, so the car wouldn’t start unless the passenger seat’s buckle was fastened. Third, the mechanisms were not reliable, so they often failed—buzzing, stopping the engine, and being an overall nuisance. Those people who couldn’t figure out how to disconnect the forcing function simply buckled the belts permanently, fastening the buckle when the seat was unoccupied and stuffing it under the seat. So if a passenger really wanted to use the belt, it couldn’t be done. Moral: it isn’t easy to force unwanted behavior upon people. And if you are going to use a forcing function, make sure it works right, is reliable, and distinguishes legitimate violations from illegitimate ones.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2570-2584的标注 | 添加于 2015年3月10日星期二 下午3:01:32
In the field of safety engineering, forcing functions show up under other names, in particular as specialized methods for the prevention of accidents. Three such methods are interlocks, lockins, and lockouts. An interlock forces operations to take place in proper sequence (figure 5.4). Microwave ovens and television sets use interlocks as forcing functions to prevent people from opening the door of the oven or taking off the back of the television set without first turning off the electric power: the interlock disconnects the power the instant the door is opened or the back removed. The pin on a fire extinguisher or hand grenade and the safety on a rifle are other examples of interlocks; these forcing functions prevent the accidental use of the devices. A lockin keeps an operation active, preventing someone from prematurely stopping it. The sad stories of those who turn off word processors without first saving their work could be avoided with the use of a lockin. Suppose the on-off switch were a “soft” switch, not really disconnecting the power, but sending a signal to the program to quit, checking that all files had been saved, and then, after all the appropriate housekeeping operations had been completed, turning off the power. (Of course, a normal power switch should also exist as an override for special situations or for when a software problem causes the soft switch to fail.) A lockout device is one that prevents someone from entering a place that is dangerous, or prevents an event from occurring. A good example of a lockout occurs in stairways of public buildings, at least in the United States (figure 5.5). In cases of fire, people have a tendency to flee in panic, down the stairs, down, down, down, past the ground floor and into the basement, where they are trapped. The solution (required by the fire laws) is not to allow simple passage from the ground floor to the basement.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2758-2760的标注 | 添加于 2015年3月10日星期二 下午11:11:09
But none of these innovations takes hold because the qwerty keyboard, while deficient, is good enough. Although its antijamming arrangement no longer has mechanical justification, it does put many common letter pairs on opposing hands; one hand can be getting ready to type its letter while the other is finishing, so typing is speeded up.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2807-2811的标注 | 添加于 2015年3月10日星期二 下午11:47:57
Designers go astray for several reasons. First, the reward structure of the design community tends to put aesthetics first. Design collections feature prize-winning clocks that are unreadable, alarms that cannot easily be set, can openers that mystify. Second, designers are not typical users. They become so expert in using the object they have designed that they cannot believe that anyone else might have problems; only interaction and testing with actual users throughout the design process can forestall that. Third, designers must please their clients, and the clients may not be the users.
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Design of Everyday Things (Norman, Don)
- 您在位置 #4211-4213的标注 | 添加于 2015年3月11日星期三 下午12:02:26
Most designers today work in teams. Nonetheless, the comments I make about “the designer” apply. In fact, the better the teamwork, the more apt members are to share common modes of thinking and common sets of approaches, and thereby to fall prey simultaneously to the same problems.
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Design of Everyday Things (Norman, Don)
- 您在位置 #2912-2916的标注 | 添加于 2015年3月11日星期三 下午12:06:54
Designers have become so proficient with the product that they can no longer perceive or understand the areas that are apt to cause difficulties. Even when designers become users, their deep understanding and close contact with the device they are designing means that they operate it almost entirely from knowledge in the head. The user, especially the first-time or infrequent user, must rely almost entirely on knowledge in the world. That is a big difference, fundamental to the design.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3039-3041的标注 | 添加于 2015年3月11日星期三 下午10:10:48
The ability of conscious attention is limited: focus on one thing and you reduce your attention to others. Psychologists call the phenomenon “selective attention.” Excessive focus leads to a kind of tunnel vision, where peripheral items are ignored.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3137-3138的标注 | 添加于 2015年3月13日星期五 下午9:46:05
If you can’t put the knowledge on the device, then develop a cultural constraint: standardize what has to be kept in the head.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3187-3188的标注 | 添加于 2015年3月13日星期五 下午11:02:36
Each new feature adds yet another control, or display, or button, or instruction. Complexity probably increases as the square of the features: double the number of features, quadruple the complexity. Provide ten times as many features, multiply the complexity by one hundred.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3192 的书签 | 添加于 2015年3月13日星期五 下午11:07:12
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Design of Everyday Things (Norman, Don)
- 您在位置 #3254-3267的标注 | 添加于 2015年3月14日星期六 上午10:42:04
What is the problem? Nothing special, just more of everything. The special powers of the computer can amplify all the usual problems to new levels of difficulty. If you set out to make something difficult to use, you could probably do no better than to copy the designers of modern computer systems. Do you want to do things wrong? Here is what to do: • Make things invisible. Widen the Gulf of Execution: give no hints to the operations expected. Establish a Gulf of Evaluation: give no feedback, no visible results of the actions just taken. Exploit the tyranny of the blank screen. • Be arbitrary. Computers make this easy. Use nonobvious command names or actions. Use arbitrary mappings between the intended action and what must actually be done. • Be inconsistent: change the rules. Let something be done one way in one mode and another way in another mode. This is especially effective where it is necessary to go back and forth between the two modes. • Make operations unintelligible. Use idiosyncratic language or abbreviations. Use uninformative error messages. • Be impolite. Treat erroneous actions by the user as breaches of contract. Snarl. Insult. Mumble unintelligible verbiage. • Make operations dangerous. Allow a single erroneous action to destroy invaluable work. Make it easy to do disastrous things. But put warnings in the manual; then, when people complain, you can ask, “But didn’t you read the manual?”
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Design of Everyday Things (Norman, Don)
- 您在位置 #3348-3356的标注 | 添加于 2015年3月15日星期日 上午9:01:48
There are three requirements for a system to be explorable. 1. In each state of the system, the user must readily see and be able to do the allowable actions. The visibility acts as a suggestion, reminding the user of possibilities and inviting the exploration of new ideas and methods. 2. The effect of each action must be both visible and easy to interpret. This property allows users to learn the effects of each action, to develop a good mental model of the system, and to learn the causal relationships between actions and outcomes. The system image plays a critical role in making such learning possible. 3. Actions should be without cost. When an action has an undesirable result, it must be readily reversible. This is especially important with computer systems. In the case of an irreversible action, the system should make clear what effect the contemplated action will have prior to its execution; there should be enough time to cancel the plan. Or the action should be difficult to do, nonexplorable. Most actions should be cost-free, explorable, discoverable.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3361 的笔记 | 添加于 2015年3月15日星期日 上午9:05:11
elevator 's signal light and controller (up and down)
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Design of Everyday Things (Norman, Don)
- 您在位置 #3358-3361的标注 | 添加于 2015年3月15日星期日 上午9:05:11
Compare two different ways of getting a task done. One way is to issue commands to someone else who does the actual work: call this “command mode” or “third-person” interaction. The other way is to do the operations yourself: call this “direct manipulation mode” or “first-person” interaction. The difference between these two is like the difference between being driven by a chauffeur and driving an automobile yourself. These two different modes exist with computers.21
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Design of Everyday Things (Norman, Don)
- 您在位置 #3368-3369的标注 | 添加于 2015年3月15日星期日 上午9:10:35
Third-person interaction is well suited for situations in which the job is laborious or repetitive, as well as those in which you can trust the system (or other person) to do the job for you properly.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3369-3370的标注 | 添加于 2015年3月15日星期日 上午9:10:51
Sometimes it is nice to have a chauffeur. But if the job is critical, novel, or ill-specified, or if you do not yet know exactly what is to be done, then you need direct, first-person interaction.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3376-3379的标注 | 添加于 2015年3月15日星期日 上午9:12:23
When I use a direct manipulation system—whether for text editing, drawing pictures, or creating and playing games—I do think of myself not as using a computer but as doing the particular task. The computer is, in effect, invisible. The point cannot be overstressed: make the computer system invisible. This principle can be applied with any form of system interaction, direct or indirect.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3422-3430的标注 | 添加于 2015年3月15日星期日 下午1:00:25
Seven Principles for Transforming Difficult Tasks into Simple Ones How does the designer go about the task? As I’ve argued in POET, the principles of design are straightforward. 1. Use both knowledge in the world and knowledge in the head. 2. Simplify the structure of tasks. 3. Make things visible: bridge the gulfs of Execution and Evaluation. 4. Get the mappings right. 5. Exploit the power of constraints, both natural and artificial. 6. Design for error. 7. When all else fails, standardize.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3498-3504的标注 | 添加于 2015年3月16日星期一 下午3:01:24
These first two approaches to mental aids keep the main tasks unchanged. They act as reminders. They reduce memory load by providing external memory devices (providing knowledge in the world rather than requiring it to be in the head). They supplement our perceptual abilities. Sometimes they enhance human skills sufficiently so that a job that was not possible before, or was possible only for the most highly skilled performers, becomes available to many. Don’t these so-called advances also cause us to lose valuable mental skills? Each technological advance that provides a mental aid also brings along critics who decry the loss of the human skill that has been made less valuable. Fine, I say: if the skill is easily automated, it wasn’t essential.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3579-3581的标注 | 添加于 2015年3月16日星期一 下午3:20:26
A third problem is that the person becomes a servant of the system, no longer able to control or influence what is happening. This is the essence of the assembly line: it depersonalizes the job, it takes away control, it provides, at best, a passive or third-person experience.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3581-3588的标注 | 添加于 2015年3月16日星期一 下午3:20:32
All tasks have several layers of control. The lowest level is the details of the operation, the nimble finger work of sewing or playing the piano, the nimble mental work of arithmetic. Higher levels of control affect the overall task, the direction in which the work is going. Here we determine, supervise, and control the overall structure and goals. Automation can work at any level. Sometimes we really want to maintain control at the lower level. For some of us, it is the nimble execution of the finger or mind that matters. Some of us want to play music with skill. Or we like the feel of tools against wood. Or we enjoy wielding a paintbrush. In cases like these, we would not want automation to interfere. At other times we want to concentrate on higher level things. Perhaps our goal is to listen to music, and we find the radio more effective for us than the piano; perhaps our artistic skill can’t get us as far as can a computer program.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3602-3605的标注 | 添加于 2015年3月16日星期一 下午3:26:33
In making things visible, it is important to make the correct things visible. Otherwise people form explanations for the things they can see, explanations that are likely to be false. And then they find some reason for poor performance—in this example, that the remote was not very powerful. People are very good at forming explanations, at creating mental models. It is the designer’s task to make sure that they form the correct interpretations, the correct mental models: the system image plays the key role.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3646-3648的标注 | 添加于 2015年3月16日星期一 下午3:40:22
Remember, standardization is essential only when all the necessary information cannot be placed in the world or when natural mappings cannot be exploited. The role of training and practice is to make the mappings and required actions more available to the user, overcoming any shortcomings in the design, minimizing the need for planning and problem solving.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3656-3658的标注 | 添加于 2015年3月16日星期一 下午3:48:13
If we examine the history of advances in all technological fields, we see that some improvements naturally come through technology, others come through standardization. The early history of the automobile is a good example.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3666-3670的标注 | 添加于 2015年3月16日星期一 下午3:53:39
Today’s computers are still poorly designed, at least from the user’s point of view. But one problem is simply that the technology is still very primitive—like the 1906 auto—and there is no standardization. Standardization is the solution of last resort, an admission that we cannot solve the problems in any other way. So we must at least all agree to a common solution. When we have standardization of our keyboard layouts, our input and output formats, our operating systems, our text editors and word processors, and the basic means of operating any program, then suddenly we will have a major breakthrough in usability.4
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Design of Everyday Things (Norman, Don)
- 您在位置 #3671-3678的标注 | 添加于 2015年3月16日星期一 下午3:54:54
Standardize and you simplify lives: everyone learns the system only once. But don’t standardize too soon; you may be locked into a primitive technology, or you may have introduced rules that turn out to be grossly inefficient, even error-inducing. Standardize too late and there may already be so many ways of doing the task that no international standard can be agreed on; if there is agreement on an old-fashioned technology, it may be too expensive to change. The metric system is a good example: it is a far simpler and more usable scheme for representing distance, weight, volume, and temperature than the older, British system (feet, pounds, seconds, degrees on the Fahrenheit scale). But industrial nations with a heavy commitment to the old measurement standards claim they cannot afford the massive costs and confusion of conversion. So we are stuck with two standards, at least for a few more decades.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3726-3736的标注 | 添加于 2015年3月16日星期一 下午4:14:49
Many things need to be designed for a certain lack of understandability or usability. The rules of design are equally important to know here, however, for two reasons. First, even deliberately difficult designs shouldn’t be entirely difficult. Usually there is one difficult part, designed to keep unauthorized people from using the device; the rest of it should follow the normal good principles of design. Second, even if your job is to make something difficult to do, you need to know how to go about doing it. In this case, the rules are useful, for they state in reverse just how to go about the task. You systematically violate the rules. • Hide critical components: make things invisible. • Use unnatural mappings for the execution side of the action cycle, so that the relationship of the controls to the things being controlled is inappropriate or haphazard. • Make the actions physically difficult to do. require precise timing and physical manipulation. • Do not give any feedback. • Use unnatural mappings for the evaluation side of the action cycle, so that system state is difficult to interpret.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3736 的笔记 | 添加于 2015年3月16日星期一 下午4:17:23
Egyptology, trap
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Design of Everyday Things (Norman, Don)
- 您在位置 #3746-3755的标注 | 添加于 2015年3月16日星期一 下午4:22:13
One of my students worked for a computer game company helping develop a new Dungeons and Dragons game. He and his fellow students used his experience to do a class project on the difficulty of games. In particular, they combined some research on what makes games interesting with the analysis of the seven stages of action (chapter 2) to determine what factors cause difficulties in dungeon games. 6 As you might imagine, making things difficult is a tricky business. If a game isn’t difficult enough, experienced players lose interest. On the other hand, if it is too difficult, the initial enjoyment gives way to frustration. In fact, several psychological factors hang in a delicate balance: challenge, enjoyment, frustration, and curiosity. As the students reported, “Once the curiosity is lost and the frustration level becomes too high, it is hard to get a person’s interest to return to the game.” All this has to be considered, yet the game must maintain its appeal for players of many different levels, from first-time players to experienced players. One approach is to sprinkle the game with many different challenges of variable difficulty. Another is to have many little things continually happening, maintaining the curiosity motive.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3762-3768的标注 | 添加于 2015年3月16日星期一 下午4:26:53
Early in POET I examined the modern office telephone, simple looking but hard to use. I contrasted this with an automobile dashboard that has more than a hundred controls, complicated looking but easy to use. Apparent complexity and actual complexity are not at all the same. Consider a surfboard, ice skates, parallel bars, or a bugle. All are simple looking. Yet years of study and practice are required to be good at using any of these objects. The problem is that each of the apparently simple devices is capable of a wide repertoire of actions, but because there are few controls (and no moving parts), the rich complexity of action can be accomplished only through a rich complexity of execution by the user.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3775-3777的标注 | 添加于 2015年3月16日星期一 下午4:28:15
How many controls does a device need? The fewer the controls, the easier it looks to use and the easier it is to find the relevant controls. As the number of controls increases, specific controls can be tailored for specific functions. The device may look more and more complex, but it will be easier to use.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3771-3774的标注 | 添加于 2015年3月16日星期一 下午4:28:43
Actually, increasing the number of controls can both enhance and detract from ease of use. The more controls, the more complex things look and the more the user must learn about; it becomes harder to find the appropriate control at the appropriate time. On the other hand, as the number of controls increases up to the number of functions, there can be a better match between controls and functions, making things easier to use. So the number of controls and complexity of use is really a tradeoff between two opposing factors.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3783-3784的标注 | 添加于 2015年3月16日星期一 下午4:31:10
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.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3813-3819的标注 | 添加于 2015年3月16日星期一 下午4:49:53
With a paper manuscript, you can spread the pages upon the desk, couch, wall, or floor. Large sections of the text can be examined at one time, to be reorganized and structured. If you use only the computer, then the working area (or real estate) is limited to what shows on the screen. The conventional screens display about twenty-four lines of text. Even the largest screens now available can display no more than about two full printed pages of text. The result is that corrections tend to be made locally, on what is visible. Large-scale restructuring of the material is more difficult to do, and therefore seldom gets done. Sometimes the same text appears in different parts of the manuscript, without being discovered by the writer. (To the writer, everything seems familiar.)
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Design of Everyday Things (Norman, Don)
- 您在位置 #3824-3826的标注 | 添加于 2015年3月16日星期一 下午5:01:58
It is characteristic of thought processes that attention to one aspect comes at the cost of decreased attention to others. What a technology makes easy to do will get done; what it hides, or makes difficult, may very well not get done.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3832-3832的标注 | 添加于 2015年3月16日星期一 下午5:19:04
linear sequence,
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Design of Everyday Things (Norman, Don)
- 您在位置 #3826-3835的标注 | 添加于 2015年3月16日星期一 下午5:19:19
The next step in writing technology is already visible on the horizon: hypertext.9 Here we have another set of possibilities, another set of difficulties, in this case for both writer and reader. Writers frequently complain that the material they are trying to explain is complex, multidimensional. The ideas are all interconnected, and there is no single sequence of words to convey them properly. Moreover, readers vary enormously in skill, interest, and prior knowledge. Some need expansion of the most elementary ideas, some want more technical details.10 Some wish to focus on one set of topics, others find those uninteresting. How on earth can a single document satisfy them all, especially when that document must be in a linear sequence, words following words, chapters following chapters? It has always been considered part of the skill of a writer to be able to take otherwise chaotic material and order it appropriately for the reader. Hypertext relieves the author of this burden. In theory, it also frees the reader from the constraints of the linear order; the reader can pursue the material in whatever order seems most relevant or interesting.
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Design of Everyday Things (Norman, Don)
- 您在位置 #3835-3838的标注 | 添加于 2015年3月16日星期一 下午5:30:06
Hypertext makes a virtue out of lack of organization, allowing ideas and thoughts to be juxtaposed at will. The writer throws out the ideas, attaching them to the page where they seem first relevant. The reader can take any path at all through the book. See an interesting word on the page, point at it, and the word expands into text. See a word you don’t understand, and a touch gives the definition. Who could be against such a wonderful idea?
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Design of Everyday Things (Norman, Don)
- 您在位置 #3846-3849的标注 | 添加于 2015年3月16日星期一 下午5:33:37
A footnote is essentially a signal that some comment is available to the reader. In hypertext, actual numbered footnotes will not be needed, but some sort of signal is still required. With hypertext, the signal that more information is available can be given through color, motion (such as flashing), or typeface. Touch the special word and the material appears; you don’t need a number.
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