Sean, I hope it's not a psychology class you'll be flunking!

BTW, I found a good way to get the image to look away from the image and concentrate on which direction you want her to spin and picture it. Then squint your eyes so you can barely see the image. This usually jump starts your perception into seeing her turn in the direction you desire. Very cool.

Then concentrating on just her middle foot will cause the illusion to "switch back" to the "normal", clockwise direction. In my experience.

----
Cover her feet and watch her hips. They go up slightly as she turns. (I think). The effect suggests she is spinning clockwise.

However, the shadows of her feet contradict her body.

The shadow of the foot she is spinning around (middle foot) seems to get closer and then farther away. This suggests her body is going up and down as she spins.

The shadow of the raised foot only appears when the shadow of the middle foot is closest to the actual foot, suggesting she is closest to the ground. At that point, the shadow of the raised foot moves from right to left. This shadow movement suggests that the light source is coming from behind her (which I don't think is consistent), and that she is spinning counter-clockwise.

And I mirror the girl's sentiments.

I remember a few years ago when I first started studying psychology and neuroscience that I realized that what I thought was real was simply a model the systems in my brain has been building for me.

I ran around telling everyone to believe lies if you want to get up in the morning.

Undergraduate life was weird for me. =P

Or it's possible you just can't see this illusion. There are some people who are unable to see these illusions. And no one knows why...