89 Rotary to Keypads

Based on research by the American Psychological Association, adapted by Juanita N. Baker, Ph.D..

How should we design keypads for most efficient human use? In 1953 Bell Telephone Laboratories wanted to move from the circular dial to a keypunch dialing system. Wisely, they hired human factors psychologist, Alphonse Chapanis to determine how the numbers should be arranged.  Possibilities could have included numbers 1 to 10 arrayed in circles, semicircles, diagonal slashes, with the numbers ascending or descending.

Chapanis and lab assistant Mary Lutz first wanted to find out where people expect to find numbers and letters on keys.  They asked 300 participants to place numbers and letters on the keys according to where they thought they should be. For all six different configurations of keysets, people overwhelmingly preferred numbering arrangements where numerals increase from left to right and from top to bottom.  Bell Lab’s engineer R. L. Deininger’s follow-up research showed that “these most preferred arrangements tended to be best in terms of performance.”

Chapanis’ and others’ Ergonomic research (that designed for human ease) pinpointed why B-17 bombers kept crashing on runways, improved cockpit safety, pioneered the design of video- and tele-conferencing systems, studied intelligibility of digitized speech, and championed the user’s role in human-computer interaction. Human factors must be considered in all new inventions.


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

Deininger, R.L. (1960). Human factors engineering studies of the design and use of pushbutton telephone sets. Bell System Technical Journal, 39. 995–1012.

How We Use the Research

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.

Related Research

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.

For more details see:

American Psychological Association, June 30, 2006


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