Optical illusions are often fanciful diversions that keep us keen to the fact that our own minds can not only be tricked, but often tricks itself. Some illusions are so mind-blowing that we try with all of our mental capacities to see reality, but we struggle to convince our minds that what we’re seeing isn’t actually what it appears to be. One of our favorites is the shaded shield illusion. Thanks to a phenomenon known as brightness constancy, we look at the shield above and assume that the area being pointed to by the green arrow is a lighter shade of grey than the area being pointed to by the blue arrow….