Do you see the dancer spin clockwise or counter clockwise?
Apparently if you see the dancer spin clockwise you use the right brain more and if you see the dancer spin counter clockwise you use the left brain more.
http://www.news.com.au/perthnow/story/0,21598,22492511-5005375,00.html
I found this particularly cool because of the image because it's sort of amusing focusing to make the dancer go counterclockwise then clockwise and such




















