Spinning Woman Illusion

At first glance, the silhouette is spinning clockwise. but according to the source website, and the small sample test group I showed it to; you can reverse the spinning.

Here are some hints from the test group.

You have to look down at the shadow, keep your eyes there for some seconds and then slowly move your eyes upward.
Sometimes my brain even changes the direction when I look at different parts of the figure. Dont stare at her, keep your eyes moving up and down.
when she turns clockwise she has the right foot up.. when counter-clockwise its the left foot.. just tell yourself which foot is up and she will turn in that direction..