How Do I See This Illusion?

At first, you probably see an image of some evil-looking monkeys hanging on the right side of the image. Focus your eyes in the middle of the image, right beneath the lower monkey's chin, for about a minute. While staring at that area, clicj the "Toggle Show Illusion" button. You will see an imprint of a face in the blank space left behind. If you're curious about how the face belongs to, click the "Toggle Show Face" button to reveal the reference image! You can also overlay the image over the illusion to see how it matches up.

How Does This Illusion Work?

The mind has a difficult time recongnizing faces in negative space, so on first viewing of the illusion, it is difficult for you to recongize the image as a face. When you focus on the image, an afterimage will be created in your eyes, and so when you disagble the image, the afterimage is imposed on the blank background. Because the background is blank, there is no longer any negative space, so now your mind can see the face.

Another example of this kind of illusion. At first glance, you may see a vase, but if you par attention to the negative space, you will be able to see two faces looking at each other.