After all, if we include “fluency in musical notation” in our list of musical skills, we’d knock out some big names. Frank Sinatra, for instance, couldn’t read a note. Neither can Elton John. And if we include “having two hands” in our list of required traits for a pianist, we’d be forced to exclude Paul Wittgenstein, a classical pianist who lost his right arm in the First World War, who subsequently commissioned piano concertos for the left hand from the leading composers of his day, and without whom we would not have masterpieces by Benjamin Britten, Paul Hindemith, Sergei Prokofiev, Richard Strauss, and Maurice Ravel.

But while knowledge can sometimes be a blessing, it can also be a curse. Because once people know a lot about something, it can be difficult for them to remember what it’s like not to know that much. To imagine what it’s like not having that depth of understanding.

As Chip and Nancy put it, for people afflicted with component focus, “wholes are not the ‘sum of their parts,’ they are a function of one part.” The deeper a person’s expertise, the worse this narrow focus gets. Chip and Nancy show how “the curse of knowledge” accentuates the coordination troubles caused by component focus: Experts wrongly assume that—because a subject comes so easily to them after learning about it for years—what they know is obvious and can quickly be grasped by others. Experts unwittingly create coordination snafus by failing to pass along essential information to people in other positions and fields because they assume it is self-evident. Or, when they try to pass information along, experts provide explanations they believe are easy to understand but are incomprehensible to people who aren’t indoctrinated into their circle.

But it was Stewart Resnick who helped me see another even more important fact about the silver machine—that its advantage, though real, wasn’t interesting.

The silver machine’s advantage gives it value, but the advantage isn’t interesting because there is no way for an owner to engineer an increase in its value. The machine cannot be made more efficient.

One of the advantages of having pairs to study is that we can see how two people engaged in similar activities can differ radically in how they operate. This shows that their successful practices are only partly a function of the type of work they do, and largely a reflection of how the individual is encoded. To illustrate, let's look at the other writer in our study, Barbara Tuchman.