Design of Everyday Things [70]
Conscious thought tends to be slow and serial. Conscious processing seems to involve short-term memory and is thereby limited in the amount that can be readily available. Try consciously to solve the children’s game called tic-tac-toe or naughts and crosses and you will discover that you can’t, not if you try to explore all the alternatives. How can I claim that a trivial children’s game cannot be done in the head? Because you don’t really play by thinking it through; you play by memorizing the patterns, by transforming the game into something simpler. Try playing the following game:
Start with the nine numbers 1, 2, 3, 4, 5, 6, 7, 8, and 9. You and your opponent alternate turns, each time taking a number. Each number can be taken only once, so if your opponent has selected a number, you cannot also take it. The first person to have any three numbers that total 15 wins the game.
This is a difficult game. You will find it is very hard to play without writing it down. But this game is identical to tic-tac-toe. Why should it be hard if tic-tac-toe is easy?
To see the relationship between the game of 15 and tic-tac-toe, simply arrange the nine digits into the following pattern:
8 1 6
3 5 7
4 9 2
Now you can see the connection: any three numbers that solve the 15 problem also solve tic-tac-toe. And any tic-tac-toe solution is also a solution to 15. So why is one easy and the other hard? Because tic-tac-toe takes advantage of perceptual abilities, and because you simplify tic-tac-toe by changing it in several ways, by taking advantage of symmetries, and by memorizing (“leaming”) the basic opening moves and their appropriate responses. In the end, unless someone makes a slip, two players will always draw, neither one winning.
The transformations of tic-tac-toe have made a complex task into an everyday one. The everyday version doesn’t require much mental effort, it does not require planning and thinking, and it is boring. Which is exactly what everyday tasks ought to be—boring, so that we can put our conscious attention on the important things of life, not the routine.
Conscious thought is severely limited by the small capacity of short-term memory. Five or six items is all that can be kept available at any one moment. But subconscious thought is one of the tools of the conscious mind, and the memory limitation can be overcome if only an appropriate organizational structure can be found. Take fifteen unrelated things and it is not possible to keep them in conscious memory at once. Organize them into a structure and it is easy, for only that one structure has to be kept in conscious memory. As a result of this power of organization to overcome the limits of working memory, explanation and understanding become essential components of conscious thought: with understanding and explanation, the number of things that can be kept consciously in mind expands enormously.
Now consider how mistakes might be made: by mismatch; by taking the current situation and falsely matching it with something in the past. Although we are really good at finding examples from the past to match the present, these examples are biased in one of two ways: toward the regularities of the past—the prototypical situation—or toward the unique, discrepant event. But suppose the current event is different from all that has been experienced before: it is neither common nor unique, it is simply rare. We won’t deal well with it: we are apt to classify the rare with either the common or the unique, and either of these choices is wrong. The same powers that make us so good at dealing with the common and the unique lead to severe error with the rare.
EXPLAINING AWAY ERRORS
A reformed thief, telling of his success, put it this way: “I’m telling you ... if I had a hundred dollars for every time