Draw a small X on paper. Place it on a table in front of you, an arm’s length away.
Hold a pencil, and use your other hand to cover one eye.
Reach out to where you think the center of the X is.
Uncover your eye. Try to touch the center of the X again. It may seem easier. Why? Think of your own best answer, then read our explanation below.
How It Works
A person’s eyes each give the brain a slightly different picture of what the person is looking at because they see it from slightly different positions, a few inches apart. The brain combines these two views to figure out the distance to the object. That gives a person 3D vision (depth perception). Seeing with just one eye gives the brain less information about distance and, as a result, less accurate depth perception.
