Robert Sapolsky on how the link between personality types and heart disease was discovered.
It was the mid-1950s, and he and Rosenman were having an unexpected problem with their successful cardiology practice: they were spending a fortune reupholstering the chairs in their waiting rooms. There seemed to be no end of chairs that had to be fixed. One day a new upholsterer came in to see to the problem, took one look at the chairs, and discovered the type A-cardiovascular disease link. He announced it semicryptically, with the words: What the hell is wrong with your patients? People don’t wear out chairs this way. The front-most few inches of the seat cushions and the armrests--and only the front-most few inches-- were torn to shreds, as if some very short beavers had spent the night in the office craning their necks to savage the chairs. Obviously these particular waiting rooms were far from peaceful places. The patients habitually sat on the edges of their seats while fidgeting and clawing away.