An Amazing Illusion

http://www.sandlotscience.com/Ambiguous/Ambiguous_frm.htm 

Go to this  illusion site and you will find a figure that appears to be spinning.  As you observe the figure, it is liable to change spin directions without warning.   But, amazingly, with a little practice and concentration, you should be able to make the wheel reverse its spin just thinking about it!  This is neat stuff, try it.