Study sheds light on a classic visual illusion
It’s a classic visual illusion: Two gray dots appear on a background that consists of a gradient from light gray to black. Although the two dots are identical, they appear very different based on where they are placed against the background. Scientists who study the brain have been trying to figure out the mechanism behind this illusion, known as simultaneous brightness contrast, for more than 100 years. An MIT-led study now suggests that this phenomenon relies on brightness estimation that takes place before visual information reaches the brain’s visual cortex, possibly within the retina. “All of our experiments point to the conclusion that this is a low-level phenomenon,” says Pawan Sinha, a professor of vision and computational neuroscience in MIT’s Department of Brain and Cognitive Sciences. “The results help answer the question of what is the mechanism that underlies this very fundamental process of brightness estimation, which is a building block of...