Gianni A. Sarcone and Marie-Jo Waeber: “Magic Tic-Tac-Toe”. Sarcone’s Studio. Italy and Switzerland
Our visual system can interpret colors and shades in surprising ways. With this 3×3 grid we show that our sensibility to color brightness can be easily fooled. The visual mechanism in our eye that enhances the contrast of the outline of an object relative to its background is called “lateral inhibition”. Thus, even small differences in brightness between adjacent color zones are magnified by our visual system and the brain to better distinguish them. But something strange happens when the brightness boundaries of those color zones are concealed: the cues the brain needs to trigger lateral inhibition no longer exist and consequently we become blind to variations in color brightness.