Find the green dot... or not

Ok, so tonight I was reading The Redhead Riter's blog and was fascinated by something she had posted, so here it is. Oh, please go read the whole story behind this exercise. She's an awesome gal with great insight in to life's incredible intricacies. 
Try this:

Let your eyes follow the movement of the rotating pink dot. The dots will remain only one color, pink.

However if you stare at the black '+ ' in the center, the moving dot turns to green.

Now, concentrate on the black ' + ' in the center of the picture. After a short period of time, all the pink dots will slowly disappear and you will only see a single green dot rotating.

It's amazing how our brain works. There really is not a green dot and the pink ones really don't disappear.