Are You Right or Left Brain?

This is a video clip I often use when leading sessions for trainee teachers - just to emphasise that although a group of students may all be looking at the same thing, what they actually see may be entirely different. It is amazing how in a group of people you get a broad division between those who see her twirl clockwise and those who see her go anticlockwise. Last time out of a group of fifty just one person saw her twirl both ways. For me she turns clockwise most of the time but she does occasionally flip if I concentrate. Not sure if there is any scientific cause for this but it is very odd.