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Keyboards, Codes and the Search for Optimality

In biology, as in technology, we should not confuse persistence with perfection

Robert L. Dorit

What’s Your Type?

The typewriter keyboard is clearly the product of human ingenuity and is part of a technological revolution that continues to transform our lives. The genetic code, in contrast, resides at the very core of every living organism and has been evolving for four billion years. Yet both the keyboard and the code help illustrate the ways in which the persistence of features may not in itself be proof of their superiority. Instead, persistence may simply reflect the tenacious grip of a functional solution that emerges early in the process. In other words, a feature does not have to be flawless to endure—it just has to be good enough.

Top 20 letter pairs of Proust and DickensClick to Enlarge ImageThe typewriter is one of the great inventions of the late 19th century. The mechanizing of legible writing democratized communication and broke the stranglehold exercised by clerks on written business transactions. By allowing the influx of women into business and government offices, the invention of the typewriter also served as a bridge to the feminist revolution. At the heart of this invention, since then also embedded in the modern computer, is a strange and idiosyncratic feature: the QWERTY keyboard. This particular arrangement of letters on a keyboard is the near-universal standard for the entire English-speaking world.

Why this arrangement, out of the 4 x 1026 possible ways in which the English alphabet might have been laid out on a typewriter? Surely the inventors of the typewriter, and the generations that have followed, had some explicit criteria that make the QWERTY layout the unrivaled keyboard design. As with many important inventions, the legends surrounding QWERTY far outnumber the facts. One legend has it that the QWERTY keyboard was designed to reduce typing speed (and perhaps increase accuracy) by dispersing the most common letters. Another is that this keyboard design enabled early salesmen to type certain words (including the word “typewriter”) without leaving the top row. These are plausible just-so stories, but they are hard to verify.

Perhaps the most compelling account of the origin of the QWERTY design begins with a mechanical constraint: jamming keys. Readers below the age of 35 may need to be reminded that depressing a key on a mechanical typewriter causes a metal type hammer with a letter at the end of it to rise up in an arc, strike the ink ribbon and the paper and return to its original position. The most favorable keyboard would therefore be laid out in a way that separates the most commonly occurring pairs of letters, thus minimizing the likelihood of jamming.

This explanation for the layout of the keyboard has undeniable appeal: It identifies a specific constraint, proposes a mechanism and defines optimality. If true, we would expect to see a different layout of letters in, say, a French keyboard—where common letter pairings are different than those in English—and we do. The French AZERTY keyboard positions the keys quite differently than the QWERTY.

But we cannot confuse a plausible explanation with a correct one. In order to test this scenario for the evolution of the keyboard, let’s examine the first 1,500 or so words of two well-known 19th century novels: Charles Dickens’s A Tale of Two Cities and Marcel Proust’s À la recherche du temps perdu. The charts in the second figure show digraph frequencies, reflecting how often certain letter combinations appear within words. The figure shows that the top 20 letter pairs occurring in each of these novels (and in the two languages) are indeed different (th/he/er in English, as opposed to es/en/ai in French), although some pairs are present in both charts (such as re, es and it).

The QWERTY and AZERTY keyboards certainly appear to do a reasonable job of keeping co-occurring letters apart on the keyboard, far better than a simple alphabetical arrangement (or a random arrangement) of letters would. Even on these keyboards, however, certain very common pairs occur in close proximity (th, er and ed, for instance). Even assuming that minimizing jamming is the only criterion for optimality—in itself a questionable assumption—the QWERTY/AZERTY arrangements are not the best possible solutions. They are good-enough solutions.

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