Disappearing Act: Exploratorium Exhibits. QuickTime Version. An animal that blends in with its environment is much easier to see when it's moving than when it's still.

You can only see each object when it's moving. Many animals, including humans, have specialized brain cells that detect motion. These cells receive information from light-sensitive cells at the back of the eye. As an object moves past your eyes, some of your light-sensitive cells experience rapid changes in light and dark.These rapid changes trigger your motion detector cells.

If you didn't have special motion detector cells, you wouldn't be able to pick out the objects in this exhibit. All the other clues you might use to detect an object--such as contrast, outlines, or changes in texture--are missing.

It's no accident that many animals have evolved a sensitivity to motion. In the wild, anything that moves is potentially predator or prey. An animal's survival depends on it ability to detect motion quickly.

The museum version of this exhibit was originally developed by Professor Ken Nakayama of Harvard University.