Pushing Buttons: The Invention of the Phone Keypad

Human factors redesigns the phone.

Whatever happened to the rotary phone? Psychological testing helped design the ubiquitous push-button keypad for the telephone. The late Alphonse Chapanis, PhD, PA, an industrial and human factors psychologist, took a leave of absence from his post at the Johns Hopkins University in 1953 and 1954 to work on the technical staff at the Bell Telephone Laboratories. Bell Telephone, in the days before deregulation, monopolized the industry. Thus, its determination at the time to move from rotary dials to a push-button design would change the telephone for all users.

The question facing Chapanis and lab assistant Mary C. Lutz was deceptively simple: What should a push-button telephone look like? To people who've never known anything but the simple 10-button grid (three rows, three columns with the 0 on the bottom; the star and "pound" buttons came later as well as the letters Q and Z), the problem actually required thoughtful, systematic design and testing. In the early 1990s, 10 years before his death in 2002, Chapanis reminisced about how he solved the problem of the push-button phone.

"I designed a study to determine what in human factors are called 'population stereotypes.' I wanted to find out where people expect to find numbers and letters on keys," he recalled. Chapanis and Lutz tested 300 people, 150 men and 150 women, stratified in three age groups - divided evenly between persons who claimed to be either naïve or sophisticated with regard to the use of keysets.

The researchers asked participants to place numbers and letters on the keys according to where they thought they should be. "For all six different configurations of keysets, subjects showed an overwhelming preference for numbering arrangements in which numerals increase from left to right and from top to bottom," Chapanis recalled. "The most preferred configuration is the one you will now find on all push-button telephones."

From the distance of more than 30 years later, Chapanis proudly claimed, "The arrangement that Lutz and I and [Bell Labs engineer R. L.] Deininger found best is now used on millions of telephones around the world." The application of basic psychological research to industrial design resulted in a simple keypad that seems so obvious as to have been the only possible layout. Yet as studies have revealed, that simply wasn't so.

After Chapanis returned to his academic duties, Deininger followed up by having people key numbers into various configurations of keysets. Chapanis reported that Deininger's research showed, among other things, that "the most preferred arrangements tended to be best in terms of performance." Those findings were published in 1960. Still posted on the Web (see Sources & Further Reading), the published article shows what the phone keypad might have looked like - with the numbers 1 to 10 arrayed in circles, semicircles, diagonal slashes, with the numbers ascending from bottom to top, and more. As for Alphonse Chapanis and his nascent field of ergonomics, he not only pinpointed why B-17 bombers kept crashing on the runway in World War II, but he also co-authored the first ergonomics textbook, helped improve the safety of aircraft cockpits, pioneered the design of teleconferencing and videoconferencing systems, studied the intelligibility of digitized speech, and championed the role of the user in human-computer interaction. He was president of the Society of Engineering Psychologists and the Human Factors Society (now the Human Factors and Ergonomics Society). Bringing his Yale psychology training (PhD in 1943) to a career in industry, he worked, according to his obituary in The New York Times, "to make new technologies simpler to use and work environments and systems safer and more efficient."

Somehow, Alfred Hitchcock's classic film "Dial M for Murder" would sound a lot less catchy as "Press Pound For Murder." Otherwise, the benefits of a well-designed keypad are clear. Thanks to scientific findings backed by an international standards body, callers worldwide can count on their phone having a simple, predictable layout. Having one single user interface allows not only for efficient manufacture of telephones, but for callers to use their phones quickly and with fewer errors, without have to learn new layouts for numbers and letters. Given the hundreds of millions of calls placed each day, controlled research parlayed the small but significant edge of one keypad layout into a giant productivity gain. In fact, when ergonomists compared the layout of the telephone keypad with that of the calculator, which positions the highest numbers at the top and the lowest at the bottom, the phone layout was found to be superior.

Today, it seems as if the telephone keypad has been around forever. The phone itself was only invented in 1875, however. Its development, parallel to the development of psychological science, has resulted in a communications tool of unprecedented reach and versatility.

Chapanis, A. (1967). The relevance of laboratory studies to practical situations. Ergonomics, 10, 557-577.

Chapanis, A. (1970). Relevance of physiological and psychological criteria to man-machine systems. Ergonomics, 13, 337-346.

Chapanis, A. (1999). The Chapanis Chronicles: 50 Years of Human Factors Research, Education, and Design. Santa Barbara, CA: Aegean.

Deininger, R. L. (1960). Human factors engineering studies on the design and use of pushbutton telephone sets. Bell System Technical Journal, 39, 995-1012. Available: www.bellssystemmemorial.com/pdf/touchtone_hf.pdf

Deininger, R. L. (1960). Desirable push-button characteristics. IRE Transactions on Human Factors in Electronics. Volume HFE-1, 24-30.

Lavietes, S. (2002, October 15). Alphonse Chapanis dies at 85; was a founder of ergonomics. The New York Times, A1, 25.

Lutz, M. C., & Chapanis, A. (1955). Expected locations of digits and letters on ten-button keysets. Journal of Applied Psychology, 39, 314-317.

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American Psychological Association, June 30, 2006