Stare at the grey dot in the centre of this image. Now move your head backward and forwards. As you do this, the circles will start spinning.
The dot gives our brains a fixed point. We can lock the dot down in this way. However, the grey squares that make up the circles already act peculiarly before we move our heads. They appear to be standing up, like a sort of 3D fence. If we move our heads while staring at the circles, they will not spin. It is only when they are in our outer vision that they move.
Stare at the gray dot in the center...
Now move your head forward and backward. As your head moves closer to your monitor and then back away from your monitor, the circles will appear to be spinning.