3 - Knowledge in the Head and in the World

The author opens with an anecdote about borrowing a car from a friend, who mentioned to him that he would have to shift the car into reverse gear in order to remove the key from the ignition. He would never have figured that out on his own - the normal arrangement is that the car must be in park to remove the key, and there was no indication in the vehicle itself that it was otherwise.

In another example, we can generally use foreign coinage fairly accurately - because we recognize that copper is less precious than silver, and that larger coins are worth more than smaller ones. We may not be able to gauge the exact amount, but we have a relative idea that we have received roughly the right amount of change because of these conventions. The fact that we recognize these small, round pieces of metal as currency at all testifies to the value of standards and conventions.

This is the difference between knowledge that exists in the head (a person knows because they have been told) and that which exists in the world (a person knows because they can see for themselves). Getting by in the modern world requires us to have both.

Precise Behavior from Imprecise Knowledge

The knowledge that people have of the world is often imperfect, but they are still able to take actions that achieve their desired results. The author suggests four reasons this occurs:

  1. The world-knowledge they gain in the course of performing a task replaces the head-knowledge with which they began. For example, they may have assumed at a distance of ten feet that they should push a door, but as they draw closer they notice the handle and the hinges and recognize they should pull it instead, and change their plan.
  2. Precision is not always required for success. The most efficient way to open a door is to apply a very specific amount of pressure to a very specific place - but if they push in the wrong place, the door may open, even though it takes a bit more effort. In the end, they got what they wanted.
  3. The designer assumed natural constraints that do not exist in reality. Most commonly, instructions assume that things must be done in a specific order or the end result will not be achieved. But in truth, these constraints are imaginary, and a person who does things in a different manner or in a different order can still arrive at success.
  4. The designer assumed cultural constraints that do not exist in reality. This goes to the notion that there is a "proper" way to use a device, and the designer assumes that the user will comply - but again, the user can interact with the device in a different manner and still achieve his goals.

In essence, people who are using devices are going through a trial-and-error process of discovery - if they mean to "try" the things the designer assumed they would, they will achieve success through the expected sequence of actions. If they "try" the things the designer didn't consider, they may still achieve success to their own satisfaction.

He briefly mentions the way in which illiterate people are able to get by in the world, and to do so in ways that conceal their inabilities from others - they may not be able to read the word "stop" but they recognize the octagonal red shape of the sign, and have observed other drivers stopping wherever that sign occurs. In essence, it doesn't matter that they can't read because they perform the correct action and get the desired results (avoiding getting into an accident at an intersection) by other means.

It is also the way that people can (and often do) assemble furniture without paying any attention to the instructions. They see the parts, and they know what the assembled product should look like, and they just wing it. Often, they can get it right, or have fall-back plans (nails or duct tape) when they get it wrong so that the outcome is still serviceable.


Ultimately, the real knowledge is in the world itself, and the way to do something is discovered only in doing it. Regardless of what we assume will be true before starting the task, even based on experience of what we believe to be the "same" task done in the past, we will encounter knowledge when we take action in the real world.

There are two basic kinds of knowledge:

Knowledge-of becomes knowledge-how in practice. A car fanatic may have memorized that a certain brand of car has to be shifted into reverse to remove the key, but this knowledge-of gives him no benefit if he never drives that model. It's also noted that knowledge-of is not proven true until it is put into practice: the fanatic may borrow a car from someone who has had the ignition system fixed to follow the normal rules (park, not reverse) in which case his knowledge-of leads him astray.

There is a brief mention on the importance or unimportance of gaining theoretical knowledge - much of it depends on the degree to which effort used in learning pays off in practice. A person who will spend most of their working day typing benefits from taking a course in typing because learning to do it efficiently will have a major impact on their work. A person who spends little time typing and more time doing other things might be better served by a hunt-and-peck approach to typing because the time they invest in learning the "proper" way to type is not repaid in future efficiency, given that they do not type very often. The task itself is performed in an incorrect and inefficient manner, but the return on effort is greater.

As such, most people do not spend great amounts of time gaining theoretical knowledge about tasks they do not perform very often - and in general seek to gain only as much knowledge as is needed to complete a task to a satisfactory degree.

The procedural knowledge of how to do something correctly in the sense of being most efficient and effective is difficult to record, and difficult to teach. An expert tennis player may not recognize exactly how he moves his body when serving the ball, and cannot describe it accurately to the student - it just "feels right" and his pupil may not achieve the same results by following his instructions.

Most people with talent are the same way - they do not really know how they do what they do, they just do it. When they presume to teach others, they know that the theoretical knowledge they are communicating is only a fraction of the truth. And when someone learns, there is that moment where he recognizes that what he is doing "feels right," in spite of the fact that it does not perfectly conform to his instructor's advice. (EN: my sense is that the instructor provides enough information to enable the student to get things "about right" and the student takes the last step, which includes fine details, on his own - and more, that in so doing the student may discover a better way than his teacher.)


Under normal circumstances, precise action is not at all required - and people can get by doing something that is more or less correct. Everything works out fine unless something in the environment changes, and what should be "good enough" no longer gets the job done. In those instances, a user may either recognize the need for precision and repeat the step more carefully, or he may assume that the device or system is broken and does not work right.

The example of currency is cited. The United States has tried multiple times in recent history to get the public to accept a one-dollar coin (and for what it's worth, the British and French had similar problems introducing a one-pound and ten-franc coins, respectively). The new coins were too similar in size and thickness to other denominations. The designers had taken care to make the coins distinct, but the differences were too subtle. People didn't accept the responsibility of being more careful with their change - they abandoned the coin and ridiculed the government for thinking such a silly thing would work.

The author does note that people generally don't have trouble distinguishing denominations of paper currency - which in the US at least are all of similar size, texture, color, and so on. A couple of answers are provided. Chiefly, people are used to paper currency being of a uniform size and are accustomed to looking at the denominations to distinguish them, but are accustomed to coins being of different sizes and weights. But more significantly, banknotes matter more than coins. A person who mistakes a quarter for a dollar coin stands to lose seventy-five cents, which is a trifle. A person who mistakes a one dollar note for a hundred-dollar note will lose a significant amount - hence it's worth the time to be precise when dealing with paper money.

(EN: The author does not bridge the gap here, but this is significant to design. People expect everyday objects to be simple and are not willing to invest time and effort in learning to use them precisely, but when an object is used to perform a task that has high-value and the cost of errors is significant, they will dedicate time and attention.)


The author opens with rather a bizarre example - consider that many of the stories of ancient societies are written in verse. He speculates that this is because of the constraints of memory: an orator would have to memorize a large amount of data to recite an epic poem that is thousands of lines long - and to make it easier to memorize, it was written to conform to a known pattern in terms of using meter and rhymes.

By obeying the constraints of poetry, it was easier to recite a long work precisely: the speaker who had trouble memorizing the lines would know that the line they were trying to recall ended with a word that rhymed with the one they just spoke, and that the entire line had a certain number of syllables and fell into the same pattern of stressed and unstressed ones. Knowing the constraints that indicated what word could or could not "fit" in the forgotten line helps the orator to remember the correct words.

Even in the modern day, young children can quickly memorize songs and nursery rhymes using the same mental faculties. As such, if a person who wants to teach a lesson can develop a lesson within the constraints of meter and rhyme will find their student gasps and remembers more quickly - whether the entire lesson is in rhyme or just a small part of it. Many history teachers still recite "ion fourteen hindered ninety two Columbus sailed the ocean blue" to get their students to associate the year with the event - and the students recall this rhyme decades later in their adult lives.

As an aside, he notes that the expectation that someone should be able to recite word-for-word is relatively modern. Without a printed copy to score them, there would be no ability to tell. And moreover, why should we care?

He also notes that it is quite a feat: a speaker who recited Homer's Odyssey and Iliad must memorize 27,000 lines of verse - and rhymed or not, that's quite a lot. It's also noted that speakers might shorten the tale for some audiences, which means being able to remember which bits can be left out without detracting from the story, and speakers would embellish tales and change details even during the course of a performance.

But to drag himself back from this diversion ...

Most of us today do not learn epic poems, but we still make use of constraints as a way of simplifying the things we must remember. We understand the basic properties of a dial - that it is twisted, and generally clockwise - and we assume the same constraints exist on any device that presents us with a dial - a washer or drier, a microwave oven, a toaster, a shower, etc.

When we encounter a dial that does not behave this way, there is a moment of confusion, though we generally figure out how this particular dial is different - it turns clockwise, it must be pressed down before rotating, etc. Good design tends to leverage, rather than violate, these constraints.

(EN: For everyday objects that perform tasks of little consequence, I would agree. But in some instances violation of constraints can be used to cause the user to pay attention to something rather than to be careless. For example, a key that disengages a safety device should likely be made to turn counterclockwise rather than clockwise, to ensure the user pauses to consider the possible consequences of this action.)

Memory Is Knowledge in the Head

The author begins with the story of Ali Baba - in the Arabic folktale his brother gets him to disclose the secret words to open the door to the thieves' cave and when he gets inside becomes so excited by the riches that he forgets the password and is locked in, and is killed by the thieves when they return.

For most people, forgetting a password is not quite so dire, but it is rather a problem because we have many passwords we need to remember to unlock things in the present age. It's gotten to the point where memorizing all these secret codes is too much for human memory - and many people either use the same password for everything (security gurus strongly discourage this), set an easy to remember password (ditto), or frequently have to use tools to reset passwords for their devices (which is also a security backdoor).

Many of the security procedures required are unnecessary and needlessly complex. Even security professionals admit that they do this for their own accounts while advising people to do otherwise ... the hypocrites. The main reasons they are used is to give people a false sense of security about their accounts, as well as to give the companies the ability to escape liability if security is breached (they can claim the user chose "too simple" a password and failed to opt into their enhanced security features).

And ironically, all these superficial attempts at making things more secure actually end up making them less secure. In a company where employees are required to change their passwords every three months, and there are abstract rules about what a password may and may not contain, what very often happens is that employees write down their passwords on a post-it note, kept in a nearby drawer or stuck to the bottom of their keyboard, where they can be easily found.

This also precedes the digital age: when there is a safe in someone's home or office, the combination to open the lock is generally written on a piece of paper nearby. And when people begin to learn a useful trick to disguise it, such as writing it in the format of a telephone number, thieves are pretty quick to guess. If it's easy for the legitimate owner to remember, it's also easy for a thief to discover.

And coming off the rant ...

Passwords are just one example of "secret knowledge" we need in order just to make things work. The fact that the car must be shifted into reverse to remove the key is something completely unusual and unnatural that must be remembered in order to use the vehicle (or at least to secure it between uses)

(EN: Rather than elaborate on how knowledge is an obstacle for using devices, he instead dives back into the rant about security for the rest of the section.)

The Structure of Memory

Human memory is not like computer memory - it is efficient at remembering some things and inefficient at remembering others, and it tends to decay over time. Designers should seek to have a working familiarity with human memory, as it is important to performing tasks.


One significant distinction is in short-term versus long-term memory: people remember small amounts of information for a brief period of time with little effort.

He gives the example of mathematics: people generally know their multiplication tables and can easily give the answer to a simple equation such as "nine times six" very quickly - but when it becomes "97 times 62" they have to break out pencil and paper. It's not because they do not know how to multiply, but that even a two-digit equation such as this requires them to hold too much information in mind (nine times two times ten, nine times six times ten, seven times two, seven times six times ten, and add that all together)

Short-term memory enables us to perform tasks that require us to memorize small bits of information for a short amount of time without putting any effort into committing them to memory - and then just as soon forgetting what they were. We can repeat someone's name at a party when we are introduced to them, but after seven or eight introductions we have forgotten the first person's name entirely.

He marvels a bit at the way in which "memory experts" devise mnemonic techniques to remember amazingly large amounts of information - long sequences of digits or lists of unrelated information. He carries on with this quite a while, but the admits it is a complete distraction, as most people are not memory experts and are limited to normal capacity - and while there's some argument about that is, the general consensus is about five to nine unrelated bits of information.

(EN: There's a great deal of argument over the precise amount, with a lot of qualifications about what people remember in certain circumstances - so the rule of "seven, plus or minus two" that Miller first observed in the 1960s is not to be taken as true in all instances, but a good general principle.)

One common flaw in bad design is that performing an action requires an individual to keep track of too much information, or to remember it for too long. He speculates for a moment that this may be the reason that the medical profession is notorious for having shunned digital technology and uses a great deal of ink and paper: a nurse who is dispensing medication to a ward of patients cannot remember the details (they are far too often distracted to keep this information in memory), and writing it down is faster and easier than logging into a computer for each patient they visit.

(EN: Recently visiting someone in a hospital, they seem to have gotten around this by using scanners - the nurse scans her own badge to log in, scans the patient's arm band to identify them, and gets a list for that patient on that visit. The system even locks and unlocks the drawers in which medicines are held and communicates with the inventory database.)

The author mentions a few tricks to avoid memory overload, but it seems light and random, and some of it is outdated (EN: so I'm dropping it.)


Long-term memory stores information from the past. It's generally believed that it takes more effort to get something stored in long-term memory (repetition or strong emotional impact) and it takes a bit longer to retrieve information stored in long-term memory. It's also noted that long-term memories tend to be amalgamated: when we remember something we have done several times, the memory is not of seven distinct incidents, but a blend of them, and possibly with some fabricated details tossed in to fill in the gaps.

There is a great deal of speculation and debate about the precise mechanisms of long-term memory: how long a memory is stored, how much capacity it has, and the like. People can remember the address of the house they lived in as a small child, but can't seem to recall what they had for lunch last Tuesday.

The author also seems interested in the function of sleep - as there is one theory that sleeping and especially dreaming is critical to "filing" the long-term memories, and may also be responsible for some of the inaccuracies as the mind attempts to consolidate details into "files" for storage, leaving some things out while adding filler to help it make sense as a whole.

The author touches on the difference between semantic and episodic memory, such that that things that are remembered in the course of a narrative (the steps to perform a task) are more accurate and easier to access than things remembered in arbitrary categories (the options in a menu).

Another general observation is that long-term memory works by associations, which can be systematic or arbitrary. People can be assisted to remember a detail by providing additional details from a scene. To remember what you had for lunch last Tuesday, try to recall what the weather was like that day, whom you were sitting with, what they were talking about, the color of the waiter's jacket - and the missing detail will often come to mind.

Another observation is that memory is selective. When we are in an environment, we tend to give attention to those details that seem important at the moment, and ignore those that do not seem important - so the information we notice is immediately filtered to our interest. Memory takes the information we notice and filters it further, making choices about what is important enough to be remembered. All of this is entirely arbitrary, and often quite unconscious - there are few occasions in which we make a conscious effort to influence what we will remember.

While this is an amazing trick, it also demonstrates that people do not store or manage their memories in the same way. There is no single question you could ask to prompt all people to remember a forgotten detail. And confabulation is quite common, such that a person will attest that they remember something that is completely untrue - and at the same time feel certain they are telling the truth.


Information has meaning because it relates to a practical concern (you must know this fact to perform a task successfully) or can at least be understood in the context of a subject (you know what a condenser is because it's part of your air conditioner, even if you've never seen it). Arbitrary knowledge covers the leftover bits - for which a person has no context of purpose.

A lot of practical knowledge begins as arbitrary knowledge. When you study a foreign language, you often learn vocabulary words, even if you have no need of them at the time - in the expectation that you will eventually have a practical or contextual need for them at a later time. As such, things are crammed into memory by rote and do not become associated to anything useful or meaningful until later.

A shopping list is another common example of arbitrary information. During the week, you add things as you use them up and include other household items - so you can end up with a list that contains an odd assortment of things such as "toothpicks, mustard, batteries, celery, and shoe polish." The list is not needed for a specific task, nor are they all related in any way except that you've run out of them. And the reason you use a written list is that it is difficult to remember this arbitrary list of things.

Whether a bit of knowledge is practical or arbitrary depends on the individual and the goal he needs to accomplish. If a vehicle has a plug to easily attach trailer lights, it is procedural knowledge to a person who regularly tows a trailer (that plug figures into a task they routinely perform) but it may be arbitrary knowledge to a person who never tows a trailer.

Whether knowledge is contextual or arbitrary is even more difficult to gauge, because it depends on the knowledge that exists in a user's mind at the time they gained the knowledge. The scientific name of a bird is categorical knowledge to a bird-watcher who knows the names of other species of birds, but it is arbitrary to an average person who has no existing mental schema for birds.

An object that has multiple functions often creates a context in which the user can learn them. For example, all the controls for a car's stereo system are placed on a single panel and discussed in a given section of the owner's manual - such that the operator recognizes that the "reverse" button is understood in the context of the stereo (and it has nothing to do with the movement of the vehicle).


The author seems to take an odd turn to speak about mapping, via the particular example of a motorcycle that had a turn switch on the left handlebar that was moved forward to signal a right turn and backward to signal a left. The front-back mapping to right and left was unnatural in the first place, and the rider kept signaling the wrong direction because his natural inclination was to push it forward to indicate a left turn (because it was on the left side.)

He eventually figured it out by considering the direction in which the handlebar would move when making a turn - the left side of the handlebar moved back to make a left turn and forward to make a right turn. He was able to remember it after that.

The author suggest whether the design was good or bad (though reading between the lines, he doesn't seem to be a fan), but as an illustration of the way that users attempt to make sense of things that are nonsensical - and that making sense of things enables them to remember the information better.

Approximate Models: Memory in the Real World

People create mental models as a matter of efficiency: there is simply too much data to process everything individually, and things happen to quickly to ponder and deliberate over everything. We need to take in a lot of information at a glance and take action quickly - and doing so means coming up with approximations so that we can simply do things without spending much time thinking about them.

One way to do this is through approximation - which involves a method of understanding that is not precise or even particularly accurate, but merely "good enough" to do the job. A few examples are provided.


The exact conversion of Celsius to Fahrenheit can be described as "add thirty-two to the Celsius temperature and multiply that by nine-fifths." This precise equation tells you that if it's 15 degrees Celsius, that means 59 degrees Fahrenheit.

An approximation is "double it and add 30," which yields 60 - a difference of one degree. For a person wondering whether to take a jacket as they leave the house, that's close enough.


When it is suggested that short-term memory has about seven "slots" and each new piece of information knocks out something that was in one of the slots before, this is completely inaccurate.

The longer answer is the amount of information that is held in memory depends on the nature of the information, and that an information overload may cause some items or all items to be dropped.

But at the same time, it's very useful as a basic principle for designers to consider.


The conceptual model for steering a motorcycle is that pulling back on the right handlebar turns the bike to the right and pulling back on the left handlebar turns it to the left.

The actual method by which riders steer involves turning the vehicle slightly to the opposite direction, which causes the rider to "lean into" the turn. This practice, called counter-steering, is something that experienced riders do subconsciously (so much so that in teaching advanced motorcycle training courses, they often have to show video of riders to prove it to them).


The author suggests that rounding numbers before multiplying them often provides estimates that are good enough. Take the earlier example of 27 times 293 - which can be solved (with a calculator) to result in 7911. If you round both numbers, 30 * 290 is easier to do mentally - resulting in 8700, which is only 10% inaccurate.

(EN: This goes on a while, and seems a bit hokey and rigged, as experimenting with other numbers leads to even greater inaccuracies - and he also goes through a series of things you can do to get closer to the right number. I have a hard time envisioning a situation in which it would be useful to get a quick and inaccurate number ... in which a calculator would not be nearby - most people have cell phones.)


The author goes on a side-trip about scientific knowledge and practical knowledge, which is rather long winded and boils down to "a good approximation is enough for practical purposes, so stop being such a nerd."

Knowledge in the Head

Knowledge "in the head" refers to theory, which has not been put into practice. Consider that a doctor spends a great deal of time studying the theory of medicine before he touches a patient - as well he should. It's generally not a good idea to let a person with no training fumble around with a patient to see if he can figure out what he's doing.

Another example of "knowledge in the head" can be seen in the way in which pilots steer airplanes, and land them on a foggy night. Unable to see the ground at cruising altitude, and unable to see anything at all when landing in fog, they cannot steer by looking at the ground, but have to use theoretical knowledge of flight, informed by the details they see on their instrument panels.

It's also noted that anyone who engages in planning and preparing for the future is also in the realm of mental rather than practical activity, as they are envisioning a future state that does not yet exist, and can be understood only by means of a mental model. Even when they are looking forward to doing something they have done a thousand times before, they are basing it on the theory that the next time will be like all the other times in the past.

The difficulty with knowledge in the head is in remembering it at the proper time. A plan as simple as meeting friends at a restaurant at noon for lunch requires a person to remember the place and time they need to be, at the appropriate time to initiate the action they need to take (remembering in an hour before you have to leave is no more effective than remembering it when you're already half an hour late). Even if the knowledge of the plan is firmly in your head, you have to remember it - and remember to remember it at a certain time.

While people are generally good at remembering things when cued, they are not particularly good at remembering things without a cue. We may check a calendar in the morning that indicates we have a dental appointment at 10 am - and we may remember that fact. But how do we cause it to come to mind at precisely 9:30, when we need to leave the office.

One option is to watch the clock - to keep that fact in mind until the appropriate time comes. This means spending the mental energy to check repeatedly, and to make sure we do not become engaged or engrossed with something else that would cause us to forget This is fairly effective at enabling us to take action at the appointed time, but terrible for our ability to do anything else in the meantime.

It's also noted that relying on memory is not a good technique for commonplace events. If something is very important (our wedding day) it tends to stick in the mind. Something as simple as a routine business meeting is, to a person who attends six meetings a day, not something that stands out as unusual in memory.

There's also the problem of remembering things: if you need to pick up something unusual at the store, you generally remember it. But if it's something common, it's harder. Worse still is remembering not to buy something you usually do (you buy a dozen eggs every week, but don't need to buy them this week).

We have a great array of tools at our disposal to assist in human memory: checklists, clocks, calendars, alarms, etc. and often resort to various tricks to remind ourselves of things - such as putting something we need to remember to take to work on top of our car keys.

Memory Mechanisms

There are two components to a reminder: the signal and the message. The signal is simply something that comes to our attention, and indicates there is something to be remembered. The message informs us of the thing we are supposed to remember.

Both must be present for the reminder to be effective. A signal without a message tells us to do something, but not what. The infamous "tie a string around your finger" is an example - you notice the string, but forget why it is there. A message without a signal tells us what to do, but not when to do it. Writing a note to yourself is an example - "meet John at noon for lunch" does you no good if you forget to look at the note until one o'clock.

And again, most people habituate themselves to repetitively checking things in order to remember, and this is not very efficient. To check a calendar once a day to remember something to do that day is not too burdensome. To check your watch every five minutes to see if it's time to do something is a distraction and a waste of time. Alarms and electronic reminders liberate us to some degree - as we can focus on other tasks until such time as an automated alert reminds us to do something.

The sheer number of different reminder methods indicates to us that there is a great need for assistance in remembering things. But their redundancy reminds us that none of them is completely satisfactory. If one works, we wouldn't need others.

(EN: That's true, but not the entire cause of the problem. In many instances the problem is that "alerts" are overused - particularly when people have the ability to set an alert for others, and are indiscriminate about using them. The pop-up reminder for a digital calendar becomes something a person begins to ignore because most of the alerts are false alarms - invitations to meetings he doesn't really need to attend.)

The Tradeoff Between Knowledge in the World and in the Head

Everyday life depends on both mental models and observations of present reality - though it is generally some combination of the two with which we approach each task. The author considers that there are trade-offs between the two.

World-knowledge needs no mental ability - we do not need to remember things, or even understand them particularly well, to fumble about with the things before us and try to figure out how to get what we work. It's error-prone and time-consuming, the outcome is compromised, and we gain nothing from the experience.

Head-knowledge is based on assumptions that things work a certain way, if only that things will be the same this time as they were last time, and may cause us to confidently do the wrong thing if we are not observant of differences in the present situation. It also requires to gain knowledge in advance of taking action, if only by remembering a past experience. If we depend only on this, we may find ourselves perplexed or blocked in the face of a task we have not been trained to do.

As to making design choices, the key questions are how difficult is the task and how often will the user perform it. Doing something simple (opening a door) should not require a person to study a theoretical model before attempting it. Doing something complex (flying a plane) or with dire consequences for error (performing surgery) should not be so accessible as to encourage inept tinkering.

(ENL: This is likely an important bookmark - as many who've read this book seem to miss the point that it's about everyday objects for simple tasks, and the same principles should not be applied to complex tasks or unusual situations.)

Memory in Multiple Heads, Multiple Devices

The author gives an example of a conversation in which people who attempt to help one another remember something, like directions to a restaurant or the plot of a movie - each of them knows some of the facts, and they play off one another to assemble complete information. He admits that with the ubiquity of smart phones, fewer or these conversations occur - as we just look something up if we can't remember it.

He goes on a bit of a diversion about whether this makes people in general more or less intelligent if we no longer need to remember things, and then whether the external resources we often use in our daily lives are entirely dependable. Ultimately, whether you're retrieving information from a device or from your brain, it comes out to the same thing if the outcome is good.

The argument was made before: if students use calculators, they will lose the ability to do arithmetic. It largely seems moot, as there are few situations in which the skill is really necessary and a device isn't close at hand to do it. On a societal level, if you turn off the electricity for a week everything else would shut down. We accept a dependence on technology.

Moreover, the situations in which technology is unavailable are rare, and the skills to get along without our devices and gadgets are increasingly quaint and irrelevant. On a day to day basis, the combination of people and technology makes us smarter and more productive.

Natural Mapping

The author returns to the notion of mapping with the example of a stove. A natural map would place the dials for the burners in a square, such that turning the dial on the lower right operates the front right burner, etc. But when the dials are moved to a panel in a straight line, there is no longer any clear correspondence - the user must look for a legend to indicate which dial operates which burner.

As an aside, when people have trouble figuring out which dial controls which burner on a simple stove, they wonder "How could I be so stupid?" But it's not the user's fault - it's bad design that is unintuitive and causes them to have to learn an unnatural mapping. And to make matters worse, every stove is different. There is no consistency from one brand to another, from one model to another under the same brand.

On the other hand, he lauds items that map themselves to natural movements. A bathroom faucet that turns on when a person places their hands beneath it is brilliant - thought in practice most faucets seem to turn it off prematurely. The only bone he finds to pick is that it is not expected, so a person who had never encountered an automatic faucet might not know how to operate it.

He goes back to stoves: he can't think of a way that a burner could be automatic, and placing controls too close to the burner might be hazardous, so they have to be placed in a location where the user's hand and arm are well clear of the burner when switching it on or off - though some manufacturers bungle this by placing the controls in a location where a user standing in front of a stove has to reach directly over a hot burner to switch it off.

He mentions that most appliances in the home are unlikely to be a serious concern, but industrial equipment is another matter. Selecting the wrong button, dial, or lever can lead to serious injury or even fatality, or at least a fair amount of economic waste. Arguably, workers who operate such machinery should be well-trained in its functions and alert when they are on the job - but it's entirely predictable that an untrained employee who is worked long hours will be operating the machine, so simplicity and conscientious design are still needed.

He mentions vehicles in particular, which put a large object traveling at high velocity in close in the hands of tired, inexperienced, and distracted operators - and then give them even more distractions to deal with (like the air conditioner and radio) to deal with while driving at high speed in heavy traffic. But on the bright side most manufacturers got the mapping of the window controls right.

He also lays some of the blame on the consumer himself - who fails to consider how well-designed the product is before purchasing it, and only when he gets it home discovers how difficult or even dangerous it is to use. If people were to pause to consider this, and refuse to purchase products that are poorly designed, manufacturers would certainly have to pay attention.

He does offer the excuse that the user of an object may not be the buyer of it - and in some instances there is a choice between a badly-designed product that has a feature we need and a better one that does not have that feature. But these exceptions aside, consumers should be more demanding of products rather than rewarding poor design with their shopping dollars.

Culture and Design: Natural Mappings Can Vary with Culture

There's an extended and rather bizarre example of doing a presentation in Asia using a remote control with two buttons, top and bottom. He was a bit bewildered, because it made sense to him that the top button would be "next slide" and the bottom "previous slide" - but the control was opposite.

He suggests that this is a difference in perception of time: Westerners feel that they move forward in time just as they move forward in space (I click forward to move forward to the future), whereas Easterners believe the person is fixed and that time flows past a person (I click back to push time behind me and pull the future toward me).

There's Aymara Indians of South America who regularly gesture behind themselves when they speak of the future. The western mind things that the past is behind and the future in front - but the Aymara way correlates to the future being unseen (behind your head), the present being with you, the near past being close before you, and the distant past being far before you where it cannot be seen as clearly. It's perfectly logical, but unusual to the western mind.

We also sometimes represent time on a horizontal timeline - which follows our reading direction. In English texts the past is on the left and the future on the right, but in Hebrew or Arabic the past is on the right and the future on the left.

Arguable and Arbitrary Mappings

Especially with technology, many mappings are arguable. For example, when the scroll-wheel was first added to the mouse, there was some argument as to how the wheel should function - and eventually it fell into a pattern in which moving the mouse down causes text to travel upward - because the wheel is controlling the scrolling of the window (text moves up as you scroll down using the arrow keys or the vertical scrubber) rater that the movement of the text. It was so bizarre for most users that they can adjust their settings to their preference.

With touch screens it seemed more natural for the "scrolling" that is done by dragging a finger across the screen to coordinate with the motion of text, just as if your hand were dragging a piece of paper on a desktop surface. The author notes that Apple was the first smartphone manufacturer to do this, and it may have something to do with the reason their device was perceived as being easier and more intuitive.

In aviation, the attitude indicator is a display that shows the airplane's orientation - whether the plane is leaning to the left or right along a longitudinal axis (bank and pitch). The convention is to use a black and white circle that rotates behind a fixed horizontal line, rather than rotating the line against a fixed background. Either convention would be sensible.