This is an optical puzzle, which was circulating a few years ago on the internet. Dependant on the viewers mindset, the dancer could be rotating clockwise or anti-clockwise. A popular hypothothesis is whether the brain is left or right hemispherically oriented, but I attribute the rotational direction assignment to an arbritrary unconcious brain decision based on a number of ambiguous frames.

If one percieves the left leg out, it is a rear view.......right leg out is percieved as a front view. Both are valid, but the image is ambiguous. dance_still The pervceived rotational direction is dependant on how one first sees this could be perceiving the view of the silhouette of the dancer from either the rear or the front..hence either clockwise or anticlockwise rotation.