It’s a Trick On Our Eyes and Brains

Binocular stereopsis is fundamental in the way our vision works, but how does it apply to stereograms and autostereograms? Fascinatingly, these computer-generated pictures are messing up with the way our eyes work to present us with a coherent single image in the context of a random repeating pattern.

When the viewer converges the two eyes at a point behind the pattern, autostereograms start doing their magic. At that moment, our brains are tricked into thinking that element A (seen by the left eye) and element B (seen by the right eye) form just one single image. In fact, such an image isn’t there in the stereogram; it’s in our eyes.