Each year, the Neural Correlate Society holds a contest among experts on perception and visual illusions.
No. 2: Flexible colours
One colored image can lead to several color perceptions, depending on the position of black outlines that are presented on top of the colored image. The shape of a surface depends more on changes of luminance in the visual scene than on specific colors themselves. By presenting black outlines on top of colored images, the whole area between outlines is seen as having one single color. Instead of seeing the actual colors presented at each location, our brain prefers to see one homogenous color, as surfaces in real life are usually also perceived with one single color.
