Thread the Needle

Visitors are invited to demonstrate the usefulness of binocular depth perception by trying to thread a needle with only one eye. They can "thread" the giant needle in the exhibit with a long metal rod held about at arm's length. Most people don't even come close when they first try it with one eye. After several attempts, however, they begin to get closer and closer to the target. People who have no stereoscopic vision learn to use other clues in place of two eyes.