A team of researchers from MIT has discovered evidence that a classic visual illusion known as simultaneous brightness contrast, depends on brightness estimation that occurs in the retina, not the brain’s visual cortex. For more than 100 years, researchers across the world who study the brain have been trying to figure out the mechanism behind this illusion. For their study, researchers examined blind children in India and discovered that they were receptive to this illusion almost immediately after their sight was begun after surgery. The findings could help to answer the question of what is the mechanism that carries this very fundamental process of brightness evaluation, which is a building block of many other kinds of visual studies.