Hinton’s “Lilac Chaser”
If your eyes follow the movement of the rotating pink dot, you will only see one colour, 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 only see a green dot rotating.
It’s amazing how our brain works. There really is no green dot, and the pink ones really don’t disappear. This should be proof enough; we don’t always see what we think we see.
Explanation and original source
See also: Sisters of St. Francis (St. Francis)