Optical
Illusion - The Shadow on a Checker Board
In this image the two squares
with
the mice on them are exactly the same shade of gray, believe it or not.You can see proof of this by looking at the image below, where a rectangle in the same shade of gray has been placed above the image.
If you're not convinced by the image below (Some people think that there's something suspicious about the gray rectangle) you can test the effect by printing out the image above, then cutting out the strip at the top right, which is the same shade of gray as the two squares. Place the strip over both squares and you'll see that they are a perfect match.
There's nothing special about these two squares by the way. What's happening is that when you look at the picture your brain looks at it the same way that it would look at a real checker board in the real world - and in the real world your brain compensates for the effects of shadows. Your brain knows that the square in the elephant's shadow is really a white square that's darkened by the shadow, so it lightens it up when it constructs the image.
