Illusion - Making Your Eye Feel Closed When It Isn't

Cognitive Daily has an excellent post on an interesting illusion that you can try at home.

1. Go into a room, shut the door and turn out the lights so that the room is mostly dark.
2. Wait until your eyes adapt to the darkness. You should be able to make out the basic shapes of the room from the tiny bit of light coming in from under the door.
3. Next, close your right eye and cover it with your hand. Turn the light on, keeping your eye closed and covered. Leave the light on for about a minute or until your left eye has adapted to the light.
4. Uncover your eye and look around the darkened room.

What do you see? What you might experience is an illusion discovered by researcher Uta Wolfe in which it seems that your left eye is closed, even though it is open.

"Wolfe et al. say that the effect is related to other somatosensory illusions, such as the "phantom leg" effect that amputees feel. A milder version of this effect can be experienced by most people: if you see a rubber hand in a spot where your hand could be (e.g. in front of a screen that hides your hand), then if someone scratches the rubber hand, you feel your own hand being scratched. In fact, for a wide variety of physical sensations, when the visual sense contradicts the touch sense, usually vision will win out.

That appears to be what is going on in Wolfe's team's illusion. You don't normally see your eyelid, so the only visual confirmation you get that your eye is closed is that things appear darker. The illusion takes advantage of the fact that everything appears darker when you first enter a darkened room. After a few minutes, your eyes adjust and you can see again. In the illusion, only one eye is adapted to the dark, and so while one eye sees normally in the darkened room, everything seems dark in the other eye. Even though our tactile sense tells us the eye is open, vision trumps touch, and we experience the illusion of the eye being closed."

Read More: How to Make Your Eye Feel Like It's Closed, When It's Actually Open