I've been trying to sit on this one for a while and figure it out some more..

When the foot that is swinging around on the left hand side, your supporting foot is lower. When the outswinging foot travels to the right hand side, her supporting foot is up in the air a bit...

I wish I was able to edit the picture somewhat, so that this would be opposite, i.e. her supporting foot would be lower when she's swinging onto the right...


My conclusion on how this one works is based on that upward and downwards movement.. The only constant if you take into account that people can see her spinning both ways, is her being perceived as being up on the right side, and down an the left.

How our brains perceive the upwards and downwards motions mixed with the swinging, will subtley but solidly determine which was she spins... That's my take on it anyway.

Either eliminating that perceived up and down motion, or swapping it around so that she is lower on the right now instead of the left may make the results reverse or be more varied....

I've spent way to long thinking about this one.. And almost been looking at the picture long enough to get a boner... Time to give this one away..