shamelessly copied from Michael Kleef's blog (where he took it from Michael Kordahi)

It's a test to see which side of your brain you predominantly think with.
Which way do you think she is spinning - clockwise or anti-clockwise?

Right brain thinkers see her spin clockwise. Left brain thinkers see her spin anticlockwise.

LEFT BRAIN FUNCTIONS	RIGHT BRAIN FUNCTIONS
uses logic detail oriented facts rule words and language present and past math and science can comprehend knowing acknowledges order/pattern perception knows object name reality based forms strategies practical safe	uses feeling “big picture” oriented imagination rules symbols and images present and future philosophy & religion can “get it” (i.e. meaning) believes appreciates spatial perception knows object function fantasy based presents possibilities impetuous risk taking

 See if you can make her switch direction.

FWIW I always considered myself a left-brain person, but I saw her spinning clockwise, and it took some effort to get her to change (but I can make her change direction).