Researchers thought that the eye and the brain were the big factors shaping how we see contrast. But something else is also at play.

"This is extremely valuable for people with hereditary eye disease."

Monet's paintings of London's Waterloo Bridge offer a master class in visual perception—and how a master Impressionist can manipulate it.

Your pupils and the way your eyes move while you're multitasking at work could offer a way to measure just how stressed out you are.