I finally saw it spinning anti clockwise and now I can see it change directions
fairly regularly. Not sure how it works though, sometimes it seems to 'stall' a bit
but that might be due to a varing load on the CPU, and it does not always change directions at that point.
I guess if it was a spinning cross you would just see the 'arms' shorten and lenghten and you could choose which way it was spinning, but it is a more complicated image.
Maybe your brain just gets bored after a while and decides to spin her the other
way around :)