White's Illusion
What Are Photoreceptors?
What Is Lateral Inhibition?
How Does The Hermann Grid Work?
How Do Mach Bands Work?
What Are Light Contrasts?
How Does White's Illusion Work?
White's Illusion is another example of a light contrast caused by lateral inhibition. Although the gray rectangles on the left appear to be darker than the rectangles on the right, if you scroll over the image you can see that they are actually identical. That is, they are identical in intensity, but perceptually different in lightness.
As you can see, the right rectangles are mostly surrounded by white, while the left rectangles are mostly surrounded by black. The rectangles' surroundings are changing their perceived color.
Lateral inhibition causes the rectangles, that are identical in intensity, to appear different
in lightness.
With ON-Center receptive fields, when looking at the right rectangles, light from the rectangles is being detected by the light photoreceptors in the receptive field's center and activating them. However, a greater amount of light is also being detected by the dark photoreceptors in the surround, which deactivates them, and as a result, the two regions conflict with one another making the rectangles appear lighter.
With the left rectangles, the light photoreceptors in the receptive field's center detect light from the rectangles and become active while the dark photoreceptors of the surround also become active due to the absence of light, causing the two regions to conflict with one another making the rectangles appear darker. The center wants to say that it sees light while the surround wants to say that it sees dark
Overall, the illusion occurs because receptive fields aimed at those rectangles are viewing a single color, with the same intensity, differently depending on the amount of light detected by the field's surrounding photoreceptors.