Brain hemispheres...?

I've just done an optical illusion test where there is a woman dancing (ballerina spinning really) and you have to decide if she is spinning clockwise or anti-clockwise. I chose clockwise and the answer was it could be either depending on what hemisphere of your brain is being used!! Apparently if you watch her feet you are more likely to be able to see her spinning the other way but I couldn't. Anyone know any other sites with tests like this with pics and not just asking questions? Also...I guess this is why sometimes on cars i think the alloys are spinning anti-clockwise while I know in reality that is impossible as the wheels are going clockwise. I've done a few searches and only getting word based quizzes but I'd like one with more pics like this.