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Cool Eye Tricks

Cool eye tricks

Ready to try a do-it-yourself optical illusion? Check out the games below.

Hole in the hand

What you need:
A piece of paper


Roll up a piece of paper in the shape of a tube.


Hold the tube up in front of one eye. Keep both eyes open and look forward.


Take your free hand (the one not holding the tube), and hold it up in front of the eye that is not looking through the tube. Keep this hand open with your palm facing your face. Place your open hand against the side of the tube.

What you should see:
It should look like there’s a hole in your free hand. The objects in the distance should be visible through this hole.

What happened?
Your brain takes information from both of your eyes to make one image. One eye sees a hole, and the other sees a hand. When the brain adds the images together, you see a hand with a hole in it.

Pencil test

What you need: Two pencils


Close one of your eyes.


Hold the two pencils horizontally out in front of your face and try to touch the pencils ends together, keeping one eye closed.


Now, try it again with both eyes open.

What you should experience:
It should be harder to touch the pencil ends together with one eye closed than it is with both eyes open.

What happened?
Having two eyes helps you judge depth and distance. Can you think of some other activities that would be hard with just one eye?

Ask a Scientist: Eyes at Night

Switch to video with audio description

Dr. Cheri Wiggs explains what our eyes do while we sleep and why we can't see colors well in the dark.

Last updated: June 10, 2022