Checker Shadow Illusion

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In this optical illusion, we see what appears to be a checkerboard of two different shades of gray. We also perceive a shadow coming from the cylinder. In reality, the two different shades of gray, as seen in square A and square B, are in fact the same shade. This can be proven by printing out the illusion, cutting out the two shades, and putting them side-by-side. It will then be seen that they are in fact the same shade of gray.


According to Edward Adelson, who created this Checker Shadow Illusion, because there is a shadow created by the cylinder, the visual system has to determine where the shadows are and how to compensate for them. Local contrast is something that the visual system uses to determine what effect the shadow has on the image. “In this figure, the shadow looks like a shadow, both because it is fuzzy and because the shadow casting object is visible.” So really this is not a failure of the visual system to demonstrate, it is actually the success of the visual system doing what it was meant to do.


This optical illusion really shows how the visual system is really able to work out and process things in a very meaningful way. The visual system, in this case, was able to break down the information given from the illusion and put it back together in a way that the eye and brain would be able to perceive it.

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