I am leery of that approach, especially because throughout the ages, thinkers have borrowed the latest technology as models for understanding humans only to abandon or to limit the models when technology advanced.
Don Norman, a cognitive psychologist who is especially conversant with computers, spoke of the mind in terms of computational units Norman Although the analogies are usually enlightening, some scholars tend to overapply the metaphor of the moment.
We must monitor this tendency carefully lest we reify the analogies without neurophysiological support. In the seventeenth century, the universe and its denizens were often spoken of in terms of clockwork Dijksterhuis , p. In the nineteenth century, the metaphor of the steam engine permeated many philosophical musings on human function; now we know that the analogy's value is limited primarily to explaining metabolism, insofar as the metabolic system is a heat engine.
These treatments, however fascinating to read, unfortunately turn out to be of no use in the design of human-machine interfaces. Without direct evidence of functional parallelism in hand, it is wise to avoid taking computer-brain metaphors too literally. Because concerns about what is conscious and unconscious usually seem remote from our workaday world, let us tangibly demonstrate their reality in your life by means of a question: What is the final character in your first name?
Until you read the previous sentence, you were probably not thinking about this alphabetic character and its relationship to your name. You were not thinking of it; you were not considering it. Or, to use our preferred terminology, you were not conscious of it. The information was not being accessed, yet you could recover it on demand. We will call that place from which the character was fetched the cognitive unconscious. The cognitive unconscious may not be a physical place, although it must be represented by physical phenomena in the brain.
For example, when you became aware, or conscious, of the alphabetic character, this becoming might have been a change of state. Alternatively, perhaps our brains use a pointer mechanism, and a pointer was changed while the memory or thought was left where it was in your brain. It is possible that thoughts and memories could be distributed, like a holographic record of an image.
We could consider other mechanisms or descriptions, but we have no need to do so. For our purposes, all we need is to acknowledge that you were not conscious of the character at one moment and were conscious of it at another moment. I use a positional metaphor from time to time, speaking of a thought as moving from the conscious to the unconscious or back, but you should not think of this verbal convenience as denoting a model of how the brain works.
Research into the physical brain may show such a model to be valid, but that is not our concern here. When I use the terms conscious and unconscious in this book, I will generally intend them as abbreviations for the cognitive conscious and the cognitive unconscious. This change of state of your thought, from unconscious to conscious, demonstrates that you have at least two forms of knowing. To build a science of cognetics, we must banish solipsism and assume that other humans would make the same observations about their mental processes as you just did about yours.
A stimulus, such as reading a particular portion of this book, can trigger the migration of not only an item of information but also a sensation, a feeling, or another aspect of your memory or knowledge from the unconscious, where it is stored, to the conscious, where you are aware of it. Notice how your clothes feel: where they are tight and where they are loose. Until you came across the sentence that directed your attention to your clothes, you probably were not consciously aware of the various pressures that your clothes were putting on portions of your body.
I trust that these experiments on your part have convinced you that you have a cognitive unconscious and a cognitive conscious and that a stimulus can bring a mental construct from the former to the latter.
By definition, you cannot experience, or be conscious of, any unconscious process. An unconscious process, such as the one that monitors your bladder pressure, can be a stimulus, whereupon the need to relieve yourself becomes conscious. A bothersome philosophical question in connection with the previous sentence is: Who is the "you" about whom I am talking? Can I distinguish between you and your conscious? Taking an engineering perspective, I sidestep this question, saying simply that the "you" in this case is the union of your physical self and all of the physical and mental phenomena that your physical self manifests.
We do not have to address the question of the possible distinctions among you, your conscious, and your unconscious to understand interface-design principles. Stimulating one place may reproducibly call up a particular memory, feeling, or sensation; stimulating another place may reproducibly evoke a different experience. Studies of the brain performed with such techniques as magnetic-resonance imaging MRI and positron-emission tomography PET are helping researchers to elucidate the physical correlates of various mental activities.
Interface testing in the future may well make increasing use of direct measures of brain activity, but a further exploration of these methods lies outside the scope of this book. Our examples so far have followed mental constructs from unconscious to conscious. After you return to reading, your knowledge of the event will move from the cognitive conscious to the cognitive unconscious. There are borderline cases, and there is much that we do not understand about the conscious and the unconscious.
For example, you sometimes feel that someone's name is on "the tip of your tongue"; you can almost think of the name, but you cannot quite do so. Sometimes, the memory becomes fully conscious and you recall the name. Other times, the memory remains elusive. Is there a state between the conscious and the unconscious?
Have we caught the mind in the middle of "moving" the information about the name from one region of the brain to another? Is an almost remembered name evidence for a link partially formed or intermittently connected, sputtering like a loose electrical contact? Such open questions are interesting, but we do not need to answer them, just as in cosmology, we can understand that the universe is expanding, without having a clue about what happened before the expansion started, that is, before the bigbang event that most cosmologists believe was the raising of the curtain on our universe.
As I have said, I do not want to reify any particular metaphor of how the brain works. However, we cannot avoid building mental models of our brain: We build these models of our brain in our brain, a mind-boggling thought.
For the time being, then, picture the conscious and the unconscious as separate compartments. These compartments are more than just different places or states for storing thoughts or memories: They have different ways of interacting with the world and with concepts. As has been elucidated by cognitive psychologists over the past century, the cognitive conscious and the cognitive unconscious have properties beyond our awareness and unawareness of them.
Table 2. Only when you are conscious of a proposition can you determine whether it is logically consistent. The cognitive conscious operates sequentially and can consider only one question or control only one action at a time.
You can be conscious of only between four and eight distinct thoughts or things at once. Your conscious memory fades in, at most, a few seconds. The conscious is invoked in branching tasks. It is sometimes difficult to distinguish a branching task from a nonbranching task.
For example, braking for a traffic light may be either. However, if a light that you are approaching turns yellow, such that you have to decide whether to continue through the intersection without pause or to stop, your cognitive conscious comes into play.
While you are learning a task, you may see and react to it as a branching event requiring conscious attention. With repetition, your execution of the task may become nonbranching and automatic.
In Section , we start looking into these properties and their implications for interface design. Cognetics and the Locus of Attention Locus of Attention You have a degree of control over making unconscious thoughts conscious, as you demonstrated when you brought the final character of your first name "into mind. But in a few moments, unless the conversation stays on elephants, the animal will fade into the boy's unconscious. When that happens, the boy is no longer paying attention to the thought of an elephant: The elephant is not his locus of attention.
I use the term locus because it means place, or site. The term focus, which is sometimes used in a similar connection, can be read as a verb; thus, it conveys a misimpression of how attention works. When you are awake and conscious, your locus of attention is a feature or an object in the physical world or an idea about which you are intently and actively thinking. You can see the distinction when you contemplate this phrase: "We can deliberately focus our attention on a particular locus. If you hear a firecracker unexpectedly exploding behind you, your attention will be drawn to the source of the sound.
Focus is also used to denote, among the objects on a computer display, the one that is currently selected. Your attention may or may not be on this kind of focus when you are using an interface. Of all the world that you perceive through either your senses or your imagination, you are concentrating on at most one entity.
Whatever that one object, feature, memory, thought, or concept might be, it is your locus of attention. Attention, as used here, includes not only the case of actively paying attention but also the passive case of going with the flow, or just experiencing what is taking place.
You see and hear much more than whatever is the locus of your attention. If you go into a room to look for a misplaced item, what you seek may be plainly in view but remain unnoticed. We can demonstrate through optical considerations that the image of the sought object was on your retina; it might even have been within the 5-degree cone of your foveal vision.
We know through experiments in neurophysiology that a signal representing the object was being generated and transmitted over the optic nerve, yet you do not notice it, because it never became your locus of attention.
If I listen for them, I notice that the fluorescent lights in the hall near my office buzz annoyingly, but otherwise I do not hear them. The sound is there, as a tape recording can demonstrate, even when I am unaware of it.
I most often notice the sound when I turn the lights on or off. Indeed, what seems to be a full-fidelity recollection of the sound I had just been hearing suddenly becomes my locus of attention. In particular, visual perceptions decay in typically milliseconds msec , with a range of 90 msec to 1, msec; auditory perceptions decay in typically 1, msec, with a range of msec to 3, msec Card, Moran, and Newell , pp.
I cannot now, sitting at my desk, recreate the buzz in that same vivid, immediate way as I did right after it had stopped and my attention had been directed by the sudden onset of silence to the previous presence of the sound. Perceptions do not automatically become memories. Most perceptions are lost after they decay.
One implication for interface design of the rapid decay of sense perceptions is that you cannot assume that, because someone has seen or heard a particular message 5 seconds earlier, that person will remember its wording. As the information becomes the locus of attention, it moves into short-term memory, which we define in Section ; it will persist there for as long as 10 seconds.
Juggling, table tennis, and playing piano are everyday examples in my life; they all seemed impossible when I first attempted them. Walking is a more widely practiced example. With repetition, or practice, your competence becomes habitual, and you can do the task without having to think about it.
Lewis Thomas , whose writings on biology are always a joy to read, expanded lyrically on the subject. Working a typewriter by touch, like riding a bicycle or strolling on a path, is best done by not giving it a glancing thought.
Once you do, your fingers fumble and hit the wrong keys. To do things involving practiced skills, you need to turn loose the systems of muscles and nerves responsible for each maneuver, place them on their own, and stay out of it. There is no real loss of authority in this, because you get to decide whether to do the thing or not, and you can intervene and embellish the technique any time you like; if you want to ride a bicycle backward, or walk with an eccentric loping gait giving a little skip every fourth step, whistling at the same time, you can do that.
But if you concentrate your attention on the details, keeping in touch with each muscle, thrusting yourself into free fall with each step and catching yourself at the last moment by sticking out the other foot in time to break the fall, you will end up immobilized, vibrating with fatigue. Any habit is a surrender of detail control, but habits are essential to the earth's higher life forms.
We also use the term habit in a pejorative sense. Despite Lewis's claim that there is no real loss of authority, bad habits do develop. Habits can be so strong as to approach addiction, sometimes reaching the point of a total loss of conscious control. I am speaking not of physiological addictions here, such as to nicotine or opiates, but rather of undesired learned habits, such as nail biting.
Insofar as our conscious selves are who we are, I am reminded of Unamuno's observation: "To fall into a habit is to begin to cease to be" Unamuno Unamuno was, perhaps, warning us against the pernicious aspects of habit formation; when it comes to the routine aspects of everyday life, however, you want your conscious attention to "cease to be.
Let me see now: The engine needs to slow down, so I have to take my foot off the accelerator. Now I have to dissipate my car's kinetic energy into heat by pressing on the brake pedal Similarly, you have developed many small habits that help you to use your computer, watch, alarm clock, telephone, and every other device that has an interface.
Persistent use of any interface will cause you to develop habits that you will find yourself unable to avoid. Our mandate as designers is to create interfaces that do not allow habits to cause problems for the user. We must design interfaces that 1 deliberately take advantage of the human trait of habit development and 2 allow users to develop habits that smooth the flow of their work.
The ideal humane interface would reduce the interface component of a user's work to benign habituation. Many of the problems that make products difficult and unpleasant to use are caused by human-machine design that fails to take into account the helpful and injurious properties of habit formation. One notable example is the tendency to provide many ways of accomplishing the same task. Having multiple options can shift your locus of attention from the task to the choice of method a topic explored in Section You cannot often break a habit by an act of volition.
As often or as fiercely as you tell yourself that you will not perform the habitual action, you may not always be able to stop yourself. Say that, for example, next Sunday your car will interchange the functions of the brake and accelerator pedals. A red light will illuminate on your dashboard to warn you of this change.
You might manage to drive a few blocks successfully with the pedals reversed, but most of us would not get out of the driveway without making an error. The red light will be of no help at all. I emphasize that you cannot undo a habit by any single act of willpower; only a timeconsuming training process can undo a habit. In such a circumstance, the user is guaranteed to develop habits that will cause him errors when he attempts to use in one application a method appropriate to only the other.
Automaticity enables you to do more than one activity at a time: All but at most one of the tasks that you perform simultaneously are automatic. The one that is not automatic is, of course, the one that most directly involves your locus of attention. The more predictable, automatic, and unconscious a task becomes, the less it will degrade or compete with other tasks Baars , p. We humans apparently simulate the simultaneous accomplishment of tasks that require conscious control by alternating our attention between tasks, attending now to one, then to the others Card, Moran, and Newell , p.
You achieve true simultaneity when all but at most one of your tasks become automatic. For example, you can, at the same time, eat a snack without choking, walk without tripping, and think through a mathematics problem to a satisfactory conclusion.
You may also be working on another math problem unconsciously, but by the definition of the cognitive unconscious, you wouldn't notice that you were. I am claiming only that you cannot simultaneously work consciously on two different math problems. For most people, all of the tasks, except for finding the solution to the mathematics problem, are so well learned that they undertake these tasks on autopilot.
However, if you were practicing these simultaneous activities and suddenly discovered a nasty-tasting morsel in the snack, you would become conscious only of what you were eating.
You would no longer be conscious of the mathematics problem. Equally important as the fact that you cannot be conscious of more than one task at any moment is the realization that humans cannot avoid developing automatic responses. This idea is important enough to bear repetition: No amount of training can teach a user not to develop habits when she uses an interface repeatedly.
That we form habits is part of our fixed mental wiring; habit formation cannot be prevented by any act of volition. If you have ever unintentionally driven toward your normal workplace on a Saturday morning when you intended to go somewhere else, you've been had by a habit that formed through repetition of a fixed sequence of actions.
When you learned to read, at first you sounded out and paid attention to each letter and syllable; now I hope you read without conscious attention to the process of translating marks into words. Any sequence of actions that you perform repeatedly will, eventually, become automatic. A set of actions that form a sequence also becomes clumped into a single action; once you start a sequence that takes less than 1 or 2 seconds to complete, you will not be able to stop the sequence but will continue executing the actions until you complete that clump.
You also cannot interrupt sequences that take longer than a few seconds to execute unless the sequence becomes your locus of attention. Thus, after you take the wrong turn on Saturday, you may suddenly realize that you intended to drive in the opposite direction; this realization makes your navigation your locus of attention, and you can interrupt the automatic sequence of actions that would have led you to your workplace.
When you repeat a sequence of operations, making and keeping what you are doing your locus of attention is the only way to keep a habit from forming. This is very difficult to do. As expressed in a common phrase, our attention wanders. The inevitability of habit formation has implications for interface design. For example, many of us have used computer systems that, before they will perform an irreversible act, such as deleting a file, ask, "Are you sure?
The idea is that, by making you confirm your decision, the system will give you a chance to correct an otherwise irrecoverable error. This idea is widely accepted. For example, Smith and Duell , addressing a nursing environment, say, "If you inadvertently delete part of the permanent record which is hard to do because the computer always asks if you're sure Unfortunately, Smith and Duell are unrealistic in their assessment: You can readily make an accidental deletion even when this kind of confirmation is required.
Because errors are relatively rare, you will usually type Y after giving any command that requires confirmation. Due to the continual repetition of the action, typing Y after deleting soon becomes habitual. Instead of being a separate mental operation, typing the Y becomes part of the delete-file action; that is, you do not pause, check your intentions, and then type the Y.
The computer system's query, intended to serve as a safety measure, is rendered useless by habituation; it serves only to complicate the normal file-deletion process. The key idea is that any confirmation step that elicits a fixed response soon becomes useless. Designers who use such confirmations and administrators who think that the confirmations confer protection are unaware of the powerful habit-forming property of the cognitive unconscious see Section A more effective strategy is to allow users to undo an erroneous command, even if they have performed intervening actions since issuing it.
You cannot protect against a user developing a habit of confirming without reestablishing the decision as the locus of attention, even by making the required confirmation action unpredictable. The action that you have requested cannot be undone. It will cause permanent loss of the information in the file. If you are sure you wish to delete the information forever, type backward the tenth word in this box. Requiring this kind of confirmation is as draconian as it is futile.
Any attempt at an effective confirmation process is necessarily obnoxious because it prevents the user from forming a habitual response and from ever becoming comfortable with it. If, for legal or other reasons, a file should never be deleted by the user, it should be made impossible for such a deletion to be performed.
Such measures also create a new locus of attention; the user is not attending to the correctness of their prior response, thus frustrating the purposes of both the confirmation and the user.
No method of confirming intent is perfect. If the rationale for performing an irreversible act was flawed from the outset, no warning or confirmation method can prevent the user from making a mistake. Trapped in the Pitfall of Automaticity I was trapped in the pitfall of automaticity while I was writing this chapter: I italicized a word, then tried to unitalicize it.
In most Macintosh word processors, pressing and holding the key marked with a drawing of an apple called the Command key and then pressing and releasing the key marked with the letter T Command-T returns the text to normal status.
In Microsoft Word, however, Command-T alters the paragraph format. The only way to prevent such errors is through interface designs that take into consideration the inevitability of habit formation. This observation underlies the solution of numerous interface problems.
Many people do not believe that they or others have only one locus of attention, but experiments, described in the cited literature, strongly support the hypothesis that we are unable to attend to multiple simultaneous stimuli. This notion, which parallels our discussion on the limitations of the cognitive conscious, is sufficiently surprising to justify examining the support for it.
As Roger Penrose noted, "A characteristic feature of conscious thought Bernard Baars , a widely recognized leader in the study of the cognitive conscious, explains that when people are "asked to monitor a demanding stream of information [they are] largely unconscious of alternative streams of information presented at the same time, even to the same sensory organ.
Similarly, in absorbed states of mind, when one is deeply involved with a single train of information, alternative events are excluded from consciousness" p.
The alternative events are not loci of your attention. Common parlance recognizes this observation. For example, we may have a thought, and we may have many thoughts, but we speak of our attention only in the singular. We never speak of a person's attentions except in unrelated usages, such as unwanted attentions.
I have described how surprising events trigger conscious attention. What is salient here is that you have acquired a new locus of attention and lost the old; it is not the case that a second locus has been brought into play. An interrupting event does not need to be external: A sudden pain or the realization that it is time for an appointment may break into your cognitive conscious, derailing your current train of thought and putting it on a new track.
In other words, in the presence of the ordinary, your attention is not pulled away. You can train yourself to scan the environment consciously from time to time to notice events to which your attention would not be otherwise called. To illustrate, pilots are taught to scan their instruments regularly, without outside stimuli to initiate scanning. A scan allows pilots to detect, for example, an instrument that subtly shows an abnormal condition.
Not every instrument in an aircraft has an alarm associated with it. Nonetheless, pilots regularly fail to perform their scan when events force their attention to a particular locus. Absorption Kills People An extreme example is an accident that killed people in December Normally a green indicator in the airliner's cockpit lights to signal that the landing gear is down and ready for landing. When the indicator failed to light, the pilot decided to circle at an altitude of 2, feet, and the copilot put the aircraft on auto pilot to maintain the altitude.
All three crew members then tried to change the bulb, but it stuck and they could not get it out. Perhaps due to their moving around and working on the bulb, they accidentally turned off the autopilot; in any case, it became disengaged. Soon, as the cockpit recording later showed, an automatic warning sounded; a 0.
A yellow warning indicator also lit up. The crew, absorbed in the problem with the green bulb, failed to notice either warning. A little later, while still struggling with the bulb, the copilot noticed that the altimeter indicated feet, alarmingly low. He then asked the pilot, "We're still at two thousand, right? You can be more or less absorbed in the task that involves your locus of attention. The more intensely you are focused, the more difficult to transit to a different locus of attention, and the greater the stimulus needed to effect such a change.
In the extreme case, when we are completely absorbed by a task, we cease to monitor our environment. You have probably experienced the absorbed state when you are reading a book, are thinking deeply about a problem, or are in the midst of a crisis that, as the expression goes, demands your attention. The use of a computer is often so stressful and difficult that a user will become absorbed in working on the computer system, and therefore distracted from the completion of tasks.
Our goal is to leave the task as the locus of the user's attention. Absorption in a task or a problem decreases the ease with which a person can change her locus of attention. Systems should be designed to allow users to concentrate on their jobs. Interfaces should be designed as though the user will be so absorbed in her task that she may not respond to your attempts to communicate with her.
An interface must work, whatever the user's state of absorption. For example, interface designers sometimes assume that the user's locus of attention is the cursor and that changing the cursor's shape will inevitably command the user's attention.
The cursor location is a good place to put indicators, but even there, the indicator can go unnoticed; the shape of the cursor is not the locus of attention; rather, the place or object to which it is pointing may well be. An example is given in Section Many examples of absorption seem unbelievable until you experience a similar incident or until you have seen so many reports that you become convinced of the strength of absorption's grip.
Because aviation accidents are often well researched and carefully documented, they are a good source for case studies. Here is another Garrison A well-known pilot was flying an aircraft unfamiliar to him, one that required him to lower the retractable landing gear as he made his descent. As a reminder, a buzzer sounds when this particular model of aircraft is a certain distance from the ground and the gear has not been lowered.
This was one of my early lessons in the bizarre mental mix-ups that can lead to accidents " Garrison But there was no bizarre mental mix-up: Garrison was concentrating on making a good landing, one of the most difficult tasks that a pilot must accomplish and one that requires a great deal of concentration. This book is not the forum for a discussion of the details, but at times, automatically lowering the landing gear could be dangerous to the occupants.
Therefore, it is always left up to the pilot to choose whether to lower the gear. The human ability to tune out disturbances is not necessarily an all-or-nothing response, as in the previous examples; it can be proportional to the level of absorption and the degree of disturbance.
As stress increases, "people concentrate more and more on but a few features of their environment, paying less and less attention to others" Loftus , p.
Thus, if the computer behaves unexpectedly while you are using an interface, you become less likely to see hints, help messages, or other user aids as you become increasingly agitated about the problem. The more critical the task, the less likely it is for users to notice warnings that alert them to potentially dangerous actions. A computer warning message is most likely to be missed when it is most important for it not to be missed; this sounds like a humorous corollary of Murphy's law,[3] but it is not.
One way we can help is to make sure that users cannot make interface operation errors, or that the effects of any actions are readily reversible rather than simply notifying users about the potential consequences of their actions.
Most interface situations can be designed such that error messages are unnecessary. A forceful diatribe against using error messages appears in About Face Cooper , pp. The first corollary is, If nothing can go wrong, it will anyway.
Let us explore how we may have come to have this trait. Baars speaks eloquently to the question; he seeks a biological rationale for our having evolved in this limited fashion, asserting that consciousness and related mechanisms pose a great challenge to functional explanations because of the paradoxical limits of conscious capacity. Why can't we experience two different "things" at one time? Why is Short Term Memory[4] limited to half a dozen unrelated items?
How could such narrow limits be adaptive? Reasoning naively, it would seem wonderful to be able to consciously read one book, write another one, talk to a friend, and appreciate a fine meal, all at the same time. Certainly the nervous system seems big enough to do all these things simultaneously. The usual answers, that the limitations are "physiological" or that we only have two hands and one mouth to work with, are quite unsatisfactory because they simply move the issue one step backwards: Why have organisms blessed with the most formidable brain in the animal kingdom not developed hands and mouths able to handle true parallel processing?
And why does our ability to process information in parallel increase with automaticity, and decrease with conscious involvement? If we do not make use of the memory or make it our locus of attention, STM fades in 10 to 20 seconds, or far less if we pay attention to new events.
As Baars notes, STM is not only short but also of very limited capacity, and new events will drive out the old irretrievably. For a nontechnical and eminently readable account of the structure of human memory, see Loftus Baars suspects that the answer lies in there being only one "whole system": There is but one "I" in each of us. But to say that there is one personhood per human being begs the question. That is, why are there not multiple personhoods per mind-body ensemble?
I am speaking not of changes that occur serially,[5] but rather of true simultaneous and independent minds in a single, connected physical entity. It may simply be that having a single personhood is a biological accommodation to the linearity of time or results from an accident of evolution rather than from a functional adaptation. Nevertheless, it seems more likely that our single personhood is adaptive: an accommodation to the purely physical impediments to having multiple simultaneous persons in one body.
Given our evolved body plan, both personalities would not be able to speak at once or to turn the head in different directions simultaneously. Even if our eyes could have evolved to operate as independently as a gecko's, would they be able to serve two independent curiosities?
These changes, as well as the changes called multiple-personality disorder, are not what is being discussed. I have acted the same way myself. Sometimes, what is learned by not fleeing is of value, and sometimes the delay is fatal: whence the expression "curiosity killed the cat. Siamese twins and two-headed animals do occur from time to time, and they have two independent minds, but they are developmental accidents, a mismatching or a misreading of the genetic code.
They are not successful from an evolutionary standpoint and are not products of natural selection. In the wild, such sports of nature rarely survive and reproduce. The next step is to make use of that singularity. We can redesign neither our own internal wiring nor that of other users, but we can create products that have interfaces that accommodate these cognitive capabilities. That people have a single locus of attention is not always a drawback.
Magicians exploit this characteristic shamelessly. A good magician can fix the attention of an entire audience on one hand so that not a single spectator will see what the other hand is doing, although that hand is in no way concealed. See Computer-aided design Coaxial cables, Calculation, 47, 72, , 89, Cockpit, 25, 51, 66 95, Cognetics, 10, 12, , Calculator and ergonomics, versus computer, and interface design, Canon, and locus of attention, Canon Cat, , 30, 31, 50, , , Cognitive conscious, 13, 14, ,,,, and cognitive unconscious, Calculate key built in, limitations of, 24 disk formatting on, properties of, 16 ex-IBMers and testing, Cognitive Theory qfConsciousness, A Baars , "Local Leap" on, 11 and quasimodes, 56 Cognitive unconscious, 11, 13, 14, Use Front key on, 56, 57 habit-forming property of, 22 Caps Lock key, 39, 55 properties of, 16 Card, Stuart K.
FireWire standards, GOMS calculation examples, Fitts' Law, 71, , 97 interface timings, and penalty with small targets, GOMS model, 71 and scrolling, Grab cursor, and standard text cursor, Graphical input devices, 34, , Fixed delays, , Fixed responses buttons, 34, and confirmation steps, 22 comparative task analysis, 73 Flashlights, , 46 cursor moves with, Floppy disks, and double clicking, Fluke oscilloscope, 52, 53 and one-button mouse, Focus, with two-part cursor, versus locus, 17 and zooming, Font size and zoom quasimodes, , See also and icons, Cursors; Mouse Footnotes Graphical user interfaces, 2, 49, zooming in on, , Forward erase, for Hal's interface, 81 Four-conductor linear hermaphroditic Hal's interface: solution 2, connector, , and icons, Foveal, 17, 40, searches initiated with, -Fowles, Bob, 47 Graphics, Freud, 11 Grey, C.
See Graphical user interfaces Fundamentals importance of, xvii-xix Habit formation, ,21,22, Habituation, Games, and buttons, 52 Generated content, and Hick's Law, 96 Gestures, Hal, and comparative task analysis, 73 Hal's interfaces defined, 37 efficiency of, modal, 42 other solutions for, and monotony, 67 Handheld computers, 7 GIDs. See Graphical input devices Handheld personal data managers, xi Global Village, Handwriting tablet, Goals, objects, methods, and selection rules.
See also Input devices, computer, See Intensive care unit and universal psychological facts, 4! See and absorption, See also Humane dialog box with different, interfaces; Human-machine Lazar, David, 11 interfaces; Interface design LEAP, , , , , , Interface timings, and cursor position, Interference, 21 document selection with, Internet, xix, 12, 99, See also Locus of attention MRI.
See Positron-emission tomography Noun-verb design of commands, Photo-processing programs, PLlI, Positional cues, Oberon, Positron-emission tomography, 15 Objects Pound, Ezra, 66 actions applied to, 59 Power connectors, display states of, Preemption dilemma solution, highlighting of, Preferences, 47 and locus df attention, Pressure-sensitive graphic tablets, sameness for, Product OCR programs.
See Optical character interface as, 5 recognition programs Productivity Old selection, designing for, 5 OLE software Microsoft , Programmers, One-button mouse, 34 and documentation, history and future, Programming One-on-one interaction with human user considerate, EMBED for wordpress.
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