The image is an animated GIF with only 34 frames, so it's not switching (although there does seem to be a slight hiccup between the 34th and 1st frame).Okay assuming it's not just a simple case of switching the direction of the spin ever so often,
I'm not sure what you mean-- if that were true, wouldn't you expect to see one version if you closed your left eye, and another version if you closed your right eye?I reckon it's probably just a matter of two things being slightly out of sinc, either the frequency of spin of the lady and her shadow, or a difference in strength between the muscles in your right and left eye.
This "illusion" is also flawed due to the shadow in the forefront, moving right to left, which would be moving in the opposite direction if she were even able to spin counter-clockwise.
I think that it's just fine. When seeing her go CCW, your brain thinks the shadow is caused because she becomes closer to the ground, which causes the shadow to come into view.This "illusion" is also flawed due to the shadow in the forefront, moving right to left, which would be moving in the opposite direction if she were even able to spin counter-clockwise.
The only way the acclaimed "left brain" would be able to see her spinning CCW is if they ignored available information.
Placing my hand over the shadow, I can indeed see her spinning CCW. But, sorry, my makes use of all available info, so, given the visual information provided in the "illusion," she's spinning CW.