This video is based on an optical illusion! In the video the experimenter, Beau Lotto, shows two grey boxes, seemingly different shades of grey, and asks if they are different. Once he puts a color swatch against the two boxes you can see that they really are the exact same color. This video shows how your brain uses shadows to make decisions on what it's seeing. I'm still confused as to how this works, but it was a really interesting vision test, and made me think a lot about how we perceive everything. "What illusions tell us is that what we're trying to see is not the world as it really is, but something else."