Moving Waves Illusion

Stare on the image. Even though you're not looking at the illustration directly, you can still see it, right? (You're using your peripheral vision.) The center should look as if it's drifting down; the outer sections should appear to drift up.Its like waving up and down.
Scientists aren't sure what causes this illusion. But experts think slight color changes can trick the brain into thinking that an image is moving. This illusion—discovered by vision scientist Akiyoshi Kitaoka—is called "perceptual drift" because the brain perceives parts of the image to be drifting.