Margalit Fox, "John E. Karlin, Who Led the Way to All-Digit Dialing, Dies at 94", NYT 2/8/2013:
A generation ago, when the poetry of PEnnsylvania and BUtterfield was 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? In a circle? A rectangle? An arc?
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, a Bell Labs industrial psychologist named John E. Karlin. [...]