Kieth Lang at UI & Us tells a story of how rounded rectangles, a shape very common in Apple’s software and hardware design, took off. The primary players in this story are graphics developer Bill Atkinson, a parking sign and Steve Jobs.
Steve took Bill on a walk, pointing out the ubiquity of rounded rectangles in the world around them. Eventually a rounded rectangular No Parking sign convinced Bill.
The very next day, Bill proudly returned triumphant. Overnight he’d written code to draw rounded rectangles at turbo speeds. And once rounded rectangles were as computationally cheap to draw as square-edges rectangles, they became ubiquitous on the Mac.
Kieth does his own digging and comes up with more fascinating information about how the mind actually requires less cognitive effort to process rounded vs sharp-edged shapes.