Whenever knowledge needed to do a task is readily available in the world, the need for us to learn it diminishes. For example, we lack knowledge about common coins, even though we recognize them just fine (Figure 3.1). In knowing what our currency looks like, we don’t need to know all the details, simply sufficient knowl- edge to distinguish one value of currency from another. Only a small minority of people must know enough to distinguish coun- terfeit from legitimate money.
Or consider typing. Many typists have not memorized the key- board. Usually each key is labeled, so nontypists can hunt and peck letter by letter, relying on knowledge in the world and minimizing the time required for learning. The problem is that such typing is slow and difficult. With experience, of course, hunt-and-peckers learn the positions of many of the letters on the keyboard, even without instruction, and typing speed increases notably, quickly surpassing handwriting speeds and, for some, reaching quite re- spectable rates. Peripheral vision and the feel of the keyboard provide some knowledge about key locations. Frequently used keys become completely learned, infrequently used keys are not learned well, and the other keys are partially learned. But as long as a typist needs to watch the keyboard, the speed is limited. The knowledge is still mostly in the world, not in the head.
If a person needs to type large amounts of material regularly, fur- ther investment is worthwhile: a course, a book, or an interactive program. The important thing is to learn the proper placement of fingers on the keyboard, to learn to type without looking, to get knowledge about the keyboard from the world into the head. It takes a few weeks to learn the system and several months of prac- tice to become expert. But the payoff for all this effort is increased typing speed, increased accuracy, and decreased mental load and effort at the time of typing.
We only need to remember sufficient knowledge to let us get our tasks done. Because so much knowledge is available in the envi- ronment, it is surprising how little we need to learn. This is one reason people can function well in their environment and still be unable to describe what they do.
People function through their use of two kinds of knowledge: knowledge of and knowledge how. Knowledge of—what psychol- ogists call declarative knowledge—includes the knowledge of facts and rules. “Stop at red traffic lights.” “New York City is north of Rome.” “China has twice as many people as India.” “To get the key out of the ignition of a Saab car, the gearshift must be in re- verse.” Declarative knowledge is easy to write and to teach. Note that knowledge of the rules does not mean they are followed. The drivers in many cities are often quite knowledgeable about the of- ficial driving regulations, but they do not necessarily obey them. Moreover, the knowledge does not have to be true. New York City is actually south of Rome. China has only slightly more people than India (roughly 10 percent). People may know many things: that doesn’t mean they are true.