A really charming article about John Karlin who was one of the first UX guys. He worked at Bell Labs back in the day and helped determine lots of little details about how telephones are designed. Simple silly things like that putting a dot (to “aim” at) visible through each finger hole of a dial phone improved accuracy and speed of dialing.
He determined, through testing, the best shape (square) and arrangement (a rectangular grid) and ordering (1-2-3 in the top row) of the buttons in touch tone telephones. Yes many other options were scientifically tested.
He also tested the impact of shortening the handset cables, and whether people could handle phone numbers that didn’t include letters to aid memory.