Illusion

From the Sidney Herald Sun, an astonishing optical illusion. Does the dancer turn clockwise, or counter-clockwise.

I was absolutely convinced that, not only does the dancer turn clockwise, but there is no way to interpret the image sequence in any other way. I tried defocusing. I tried one-eyed viewing. I tried looking away. I tried sleeping on it. There's just no question.

Then I dissected the animated gif. Frame by frame: clockwise, incontrovertible.

And then, just to pin it down, I compared the frames in reverse sequence. And there, frame by frame, she's still turning clockwise.

I can find no explanation for why this illusion reflects hemispheric dominance.