Our visual system can interpret colors and shades in surprising ways. This 3×3 Tic-Tac-Toe grid, for example, showcases how easily our perception of brightness can be fooled.
Do you notice anything unusual in the grid below?
The looping animation below brings the illusion to life, revealing the trick in action. That large green square behind the grid isn’t actually uniform—it’s made up of alternating dark and light green squares. Our visual system works like a “comparative computer”. In fact, we never see colors in isolation, as the appearance of any color is affected by the colors surrounding it. So, under certain conditions, colors that are identical may appear different, while colors that are different may look the same. In our visual system there is a mechanism that enhances the contrast of the outline of an object relative to its background: it is called “lateral inhibition”.Show / Hide the Trick
Thus, even small differences in brightness between adjacent zones, or objects, are deliberately increased by our visual system and the brain to better distinguish them. But something strange happens when the brightness boundaries of the color zones are concealed: the cues the brain needs to trigger the lateral inhibition no longer exist and consequently we become blind to variations in color brightness, as shown in the animated gif.
Recognitions
My optical illusion “Magic Tic-Tac-Toe” has been chosen to be among the top 10 finalists for the “2019 Best Illusion of the Year Contest”