Yes, I know this is a suggestive silhouette that was no doubt created by a man. BUT: see if the visual effect does not bend your brain.
The question is very simple: is this figure, as viewed from the top, rotating clockwise or counterclockwise? If you’re like me, you’ll have an immediate and unshakable opinion on the matter. One glance and I was certain it was clockwise. I was so certain that I was extremely puzzled when I read that it’s possible to perceive this as rotating in the other direction. It made sense; there are no depth cues to the profile. And yet I could not imagine how I might jump start my brain into seeing it go the other way. My eye flitted away from the screen briefly, and then POP! I’m now seeing it spin counterclockwise. Now I can’t see it go the other way. Can you switch your brain from one direction to another on demand?
This short piece in the Australian Herald Sun puts a pop psychology gloss on it, which is probably about as meaningful as a horoscope, but the claim is that if you’re a clockwiser, then you’re a right-brained bearded herbal tea drinker. And you wear those weird, comfortable shoes. Otherwise, you went to MIT. Those being the only two kinds of people in the world and all.
After a little Googling, I came across this impressive site dedicated to optical illusions. His take on the spinning girl effect is that you can reverse the direction by looking at the shadow. Work for you?