Sometimes the comments are as interesting as the article...600-some for this brain hemisphere test as of a few minutes ago. I'll read them later.

More to the point, I don't see any authority/study cited to legitimize the claim that the perceived rotation relates to a dominant brain hemisphere. Maybe it does, maybe it doesn't. Maybe it's just an optical illusion, but please read on.

In any event, initially I saw it only rotating counter-clockwise, as reported earlier, while I was sitting at a library. Later, when I viewed the saved web page & test in a different environment, she appeared to be rotating clockwise. Curious, I imported the GIF from the web page into an editor and had a frame-by-frame look.

Being of a somewhat artistic bent, I was unhappy with the poorly executed animation of the Poser model: you see her elevating off her heel with each rotation, and to my eye, at least, she seems slightly out of balance and about to fall over. I wondered if certain subtle cues in the model and animation were forcing perception to favor one direction over the other. I thought such factors as camera angle, for instance, and virtual focal length might play some small but significant role. As well, some of us might pay more attention to her legs, other to her arms, others to her, ah, well...bazoobies, as an ol' pal used to call 'em.

For the sake of argument, I lent some credence to the claims of foul by a few of the people leaving comments. It would be possible, I figured, for an external script to write over the referenced animation at random with a version turning the other way. It's child's play to reverse the order of the frames in an animation.

It is true that whoever created the animation initially gave it a native rotation. It is also true that, properly done, the model could appear to spin in either a clockwise or counterclockwise direction - it would be completely ambiguous in that regard.

In order to ensure that the somewhat flubbed animation was not issuing subtle visual cues, to verify that a sequence like this could be completely ambiguous as to direction of rotation, and to make sure there was no trickery involved, I decided to create my own version of this test.

So I cranked up Poser 4 and created a model somewhat like the one I linked to in the parent of this thread. I imported the mesh to Max, made some necessary adjustments like setting the point of rotation to the correct position on the model's foot, applied a flat black material to the mesh, put a mild reflectivity to the ground, which I set to a medium gray, put my virtual camera in orthographic mode, and created a 32-frame animation of the spinning Poser 4 model, complete with ponytail and full rack.

I turned my animations into Flash SWF files and, after staring at them for probably too long, realized that I could make the animations change rotational direction at will. I restarted the saved web page and discovered that I could make that animation spin either way as well, awkward hops notwithstanding. The possibility of fraud or trickery evaporated. Perhaps it's just an acquired skill. Still, we all initially perceive her spinning one way or the other. Well, most of us, anyway.

As Raoul notes below, sometimes she just seems to be going back and forth. In all, I suppose you could say, therefore, that there are at least four different ways to perceive this simulation.

Overly proud of my work, as usual, I hastily created a YouTube account with only a few typos, uploaded my whirling dervish, and after a small wait, started the animation to see how it would all play out.

Alas, my little video won't loop on YouTube, and I'll have to leave it there, for now.

One final thought on this topic to touch on the most curious thing about direction of rotation: It all depends on your point of view.

Obviously, all the wheels on an automobile turn in the same direction, or do they? In the USA, the wheels of a car going forward rotate in a counterclockwise direction as seen from the driver's side, but in a clockwise direction as seen from the passenger side.

Around any rotating body, our universe is divided along the plane of rotation into two halves; one half sees the body rotating in one direction, while the other half sees it going the other way.

Is there any significance or utility to this observation? Obviously, it all depends on how you look at it.

Trick or Treat,
S