Are the circles moving ?
When you stare at this picture, you mind may tell you that the circles are moving, but this is impossible! How can a picture move? Some people think the circles seem to move because, often, when we see circle-in-circle shapes, like in car wheels or snake bodies, they are usually moving. Our brains are used to seeing these shapes move. So when our eyes see this shape, our mind infers that the image is moving. Other scientists believe the illusion of movement is caused by the tiny movements of our eyes as we look at the different colors and patterns of the picture.