Right... it's freaked me out so much I've researched it...

It's two pictures - two, 2D images that keep switching to give the illusion she's moving all the way around - which explains how Jackie managed to stop it. It also explains how people see her going different ways at different points.

Apparently it has bog all to do with your right/left brain. It shows how our brains haven't evolved to accept 2D images such as this - but instead have evolved to see the 3D world as it is and if it doesn't work like that our brains automatically assume that's how it should work.

Linky: http://www.theness.com/neurologicablog/index.php?p=27