I am reading Henry Petroski's Invention by Design, an interesting little book about how engineering and invention have been applied to solve such every day engineering problems as clipping papers together, storing carbonated beverages in retail-friendly containers, and crossing bodies of water.
In a sidebar, Petroski notes that telephone keypads and calculator keypads have evolved opposite standards when it comes to key ordering:
1 2 3 7 8 9
4 5 6 4 5 6
7 8 9 1 2 3
* 0 # 0 + =
(I hope my attempt at monospace formatting works here.) In telephones, "1" is at the top left and the numerals proceed across and down to "9" on the bottom right, whereas in calculators, "1" is at the bottom left and "9" the top right. I have been a regular user of both telephones and calculators for something like 30 years (though concededly, of telephones having keypads for perhaps only 20 years), and I have never once noticed this disparity of standard.
Petroski asks, "Do users who alternate frequently between telephones and calculators find the difference to be a serious problem?" From my own experience, I have to say no, patently not. How is that possible? I have no idea what the answer is but I suspect there is a psychological explanation. There must be a separation in the brain's task space between the act of punching in a telephone number on the one hand, and that of entering numbers for calculation on the other, a separation sufficient that when turning one's attention to one of the two tasks one isn't even momentarily confused by expectations associated with the other. Or something.
I am amazed that I never noticed this myself and I'll have to give some thought to why that is.