Forget the scientific nonsense, just take this simple test......
This is a static picture, if its moving then you are overtaining & you need to get a life.
( Also stare at one spot for a couple seconds and everything will stop moving. Or look at the black center of each circle and it will stop moving. But move your eyes to the next black center and the previous will move after you take your eyes away from it)
[img]http://www.smartgroups.com/picvault/17572202.jpg/untitled.jpg[/img]