Green dot illusion...

Green dot illusion...  Reader Simi L. sends along this great optical illusion.  The first effect (the green dot) I saw immediately.  The second effect (the disappearing pink dots) took longer – it requires steady focus on the black cross to see it:

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

It's amazing how our brain works. There is no green dot, and the pink ones don't disappear. This should be proof enough, we don't always see what we think we see.

One surprise for me on the second effect was that I sometimes saw some of the pink dots, but not others – they'd disappear and reappear seemingly at random.  The brain is a funny thing!