Pacman Optical Illusion

This is an amazing optical illusion.

I found this illusion on several sites on the internet. One semi-popular link farm spent 6 pages of comments discussing this optical illusion. Many were confused about what this optical illusion was all about so let's start off with the following. (If all goes well you might see something like the small image to the right).

1. The below image is an animated gif file.
2. The image is composed of 12 frames, each frame has 11 purple dots on a gray background.
3. These frames are designed so it looks as if one dot is removed at a time progressing clockwise.
4. There is no green dot in this image at all.
5. There is no green dot in this image at all.
6. There is no green dot in this image at all.
   

Stare at the center cross, you will notice a green dot start going around the circle. As you continue to stare the green dot will appear to consume the purple dots until all that is left is the green dot circling the cross, then the purple dots will reappear one by one until they are all visible again.

Jeremy L Hinton
Copyright 2004
Used w/permission

Simply put the reason you see the green dot is because that is the afterimage (or negative) of magenta.

For a more thorough explanation of how this optical illusion works go here.