18000 Hz Sine Wave: it's the frequency a human being stops hearing at about the age of 20. A girl trying to tell you she's 18 when you suspect she's 25? There's an easy way to test it, and you can find the sound sample on Youtube with ease.

Stare at the central point (plus sign) of the black and white picture for at least 30 seconds and then look at a wall.

If you're suffering from an injury, try looking at the injured part through the wrong end of some binoculars. Your pain should decrease gradually.

Stare at the eye of the red parrot while you slowly count to 20, then immediately look at one spot in the empty birdcage.

You need three people for this. One of them wears a headset connected to routine plastic pipes on the either side and sits on a chair inbetween the two observers. Each of them hold the pipes from the headset on the corresponding sides and say something into the pipes, one after another. The subject will rightly tell the direction of the sound. Exchange the pipes and repeat voicing into the pipes. Their brain will get confused and point in the opposite direction of sound.

Lift your right foot a few inches from the floor and then begin to move it in a clockwise direction. While you’re doing this, use a finger your right index finger to draw a number 6 in the air. Your foot will uncontrollably turn in an counterclockwise direction. See if you can stop it from doing so.

Look at the very center of this illusion and then slowly move your face closer to it. The 2D picture should look like a 3D tunnel. Now try it with one eye closed. See how the illusion stops? It's because the illusions come from your brain trying to handle the perception and failing.

1) Tune a radio to a station playing static. 2) Lie down on a couch and tape a pair of halved ping pong balls over your eyes. 3) Save on LSD.

Have two people sit on chairs, with one person facing the back of the other. The person in the rear wears a blind fold. The blindfolded person then reaches around and touches the nose of the person in front, and places his other hand on his own nose, then begins gently stroking both noses. Over 50% of the subjects report their nose starts feeling incredibly long. It's called the Pinocchio’s Effect.

The rubber hand illusion is an experiment where human participants view a dummy hand being stroked with a paintbrush, while they feel a series of identical brushstrokes applied to their own hand, which is hidden from view. The illusion that the dummy hand is the subject's own hand is haunting.

Take a look at the spinning girl. Do you see her spinning clockwise or counter-clockwise? You should be able to switch it in the other direction, if you focus hard enough. Give it a try.

Couldn't do it? Here's some help.