Galileo's Optical Illusion

Why does a light-colored object on a dark background appear larger than a dark object on a light background?  It's true, and you might have had this experience yourself. In the photo above, the brighter Venus (lower dot) appears larger than the dimmer Jupiter (upper dot).
Well until recently, no one knew why. Now it seems that a neuroscientist at the State University of New York's College of Optometry may have the answer. Check out the article in LiveScience.