NEW YORK — A generation ago, when poetic exchanges such as PE-nnsylvania and BU-tterfield were about to give way to telephone numbers in unpoetic strings, a critical question arose: Would people be able to remember all seven digits long enough to dial them?
And when, not long afterward, the dial gave way to push buttons, new questions arose: Round buttons, or square? How big should they be? Most crucially, how should they be arrayed?
For decades after World War II, these questions were studied by a group of social scientists and engineers in New Jersey led by one man, Bell Labs industrial psychologist John E. Karlin, who died Jan. 28. He was 94.
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By all accounts a modest man despite his variegated accomplishments (he had a doctorate in mathematical psychology, was trained in electrical engineering, and had been a professional violinist), Mr. Karlin was virtually unknown to the general public.
But his research, along with that of his subordinates, quietly yet emphatically defined the experience of using the telephone in the mid-20th century and afterward, from ushering in all-digit dialing to casting the shape of the keypad on touch-tone phones. And that keypad, in turn, would inform the design ofother everyday objects.
It is not so much that Mr. Karlin trained midcentury Americans how to use the telephone. It is, rather, that by studying the psychological capabilities and limitations of people, he trained the phone, then a rapidly proliferating but still fairly novel technology, to assume optimal form.
The design of the touch-tone keypad, the shape of its buttons, and the numbers’ position — with ‘‘1-2-3’’ on the top row instead of the bottom, as on a calculator — all sprang from research conducted or overseen by Mr. Karlin.
The push-button phone was introduced on Nov. 18, 1963, in two Pennsylvania communities, Carnegie and Greensburg.
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The legacy of the research done by Mr. Karlin’s team extends far beyond the telephone: The keypad has become the international standard on objects as diverse as ATMs, gas pumps, door locks, vending machines, and medical equipment.
Mr. Karlin, associated from 1945 until his retirement in 1977 with Bell Labs, headquartered in Murray Hill, N.J., wascalled the father of human-factors engineering in US industry.
A branch of industrial psychology that combines experimentation, engineering, and product design, human-factors engineering is concerned with easing the awkward, often ill-considered marriage between human and machine. In seeking to design and improve technology based on what its users are mentally capable of, the discipline is the cognitive counterpart of ergonomics.
Among the issues Mr. Karlin examined as the head of Bell Labs’ Human Factors Engineering department — the first department of its kind at a US company — were the optimal length for a phone cord (a study that involved gentle, successful sabotage) and the means by which rotary calls could be made efficiently after the numbers were moved from inside the finger holes, where they had nestled or years, to the rim outside the dial.
John Elias Karlin was born in Johannesburg .
He earned a bachelor’s degree in philosophy, psychology and music, and a master’s degree in psychology, both from the University of Cape Town. Throughout his studies he was a violinist in the Cape Town Symphony Orchestra.
Moving to the United States, Mr. Karlin earned a doctorate from the University of Chicago in 1942. Afterward, he became a research associate at Harvard; he also studied electrical engineering there and at Massachusetts Institute of Technology.
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At Harvard, Mr. Karlin did research for the US military on psychoacoustics, vital to the war effort — studying the ways, for instance, in which a bomber’s engine noise might distract its crew from their duties.