Strange Phenomenon

Here's a simple thing to try:

1. Start spinning clockwise circles with your right foot.
2. Now hold up your right hand in front of you and try to draw the number "6" in the air.

When you do this can you keep your foot moving in the same clockwise direction or does the simple movement of your hand mess up what you're trying to do with your foot?

I can't and anecdotal evidence has revealed that most people can't either. I'd LOVE to hear a definitive scientific answer about why this occurs!