Nänni confirmed my theory: “You are absolutely right. A rectangle with sharp edges takes indeed a little bit more cognitive visible effort than for example an ellipse of the same size. Our “fovea-eye” is even faster in recording a circle. Edges involve additional neuronal image tools. The process is therefore slowed down.”
Professor Nänni is saying that rounded rectangles are literally easier on the eye. Put another way, compared to square-edged rectangles, rounded rectangles are more computationally efficient for the human brain. To me, this is a revelation. An idea that at the very least demands more investigation.
Rounded rectangles have been a staple of UI design since the dawn of the graphical user interface. Lately there has been an increasing number of sharp-edged rectangles used in UI designs, specifically in buttons and forms. For instance, Material Design uses nearly-straight edges throughout its UI components.Written on June 25th, 2015