Dancing Lady

Thanks are due to the naughtiest guy in class for this. It's not spectacularly amazing or anything, but just pure fun, and really, really, time consuming.

Which direction is this lady dancing in? She is definitely spinning, and she is spinning backwards (for herself). But is she going clockwise or counterclockwise?

There are probably hundreds of such trick images circulating the internet, each one perhaps equally interesting, because each probably presents a different trick, or a different way in which our mind plays tricks on us. Of course this particular one has no answer, because depending on how you see it, she can be moving in either direction. If you try hard enough, you can see both types of spin, and you can even train yourself to make her change direction at will. It's actually really simple: you just have to figure out that critical point of her spin, from where your brain starts to pick up on the direction of her motion. If you happen to start looking at her only from that critical point onwards (achieved easily and simply by a quick shutting and opening of the eyes), you can make her change direction. It's important not to preserve the image of her motion in the mind as you're trying this.

If you received this in a chain mail or forwarded message over the internet, you probably also got a lot of text about left brain and right brain and their relative abilities and so on and so forth. While all of that is probably very interesting, it is perhaps best left to the explanatory capabilities of Wikipedia or some other reliable encyclopedia. For the moment, concentration on enjoying the illusion. This is magic at its best -  the magic of the human mind.

(Image courtesy http://www.nicholasroussos.com/ who're hosting it up there for people to link to)