Is there a universal law of ponytail rotation?

I was observing girls jogging on a visit to my sons campus and noticed an interesting phenomenon. Their ponytails all seem to rotate in the same direction. Nearly always in a figure 8 pattern, rising on the left side and descending on the right. This leads me to wonder about the physics of hair and perhaps a unified theory of hair rotational gravity. Or perhaps I have way too much time on my hands. At any rate, has anyone any ideas? Will their hair reverse direction after December 12th?