Don’t we just love to test ourselves to see “which one” we are! I think I did this test years back. Perhaps you’ve seen it? Can you see the dancer turning clockwise or anti-clockwise?
If clockwise, then you use more of the right side of the brain. And vice versa. Most see her turning anti-clockwise. Which I find IMPOSSIBLE to fathom. I can only see her going clockwise. Surprising…I’ve always convinced myself I’m completely left brained – rational, logical etc.
See the rundown of the right and left-brain functions. Apparently you can try to focus and change the direction.
Since I posted this, reader Teresa sent me a link to a site that explains how this works (and that the right/left brain divide isn’t accurate – we use both in tandem)…
What they reveal is how our brain processes visual information in order to create a visual model of the world. The visual system evolved to make certain assumptions that are almost always right (like, if something is smaller is it likely farther away). But these assumptions can be exploited to created a false visual construction, or an optical illusion.
The spinning girl is a form of the more general spinning silhouette illusion. The image is not objectively “spinning” in one direction or the other. It is a two-dimensional image that is simply shifting back and forth. But our brains did not evolve to interpret two-dimensional representations of the world but the actual three-dimensional world. So our visual processing assumes we are looking at a 3-D image and is uses clues to interpret it as such. Or, without adequate clues it may just arbitrarily decide a best fit – spinning clockwise or counterclockwise. And once this fit is chosen, the illusion is complete – we see a 3-D spinning image.