‘Proprioception’ is the sense of your own body; the understanding of the position of your limbs relative to each other. You can investigate, and fiddle with, this sense with these simple illusions.
1 - Rubber hand illusion
This is a classic experiment to trick your sense of self. Sit someone down with a stuffed rubber glove in front of them, and their actual hand hidden from view. Stroke both the rubber hand and real hand for about a minute, and they should start to feel like the rubber hand is theirs! Test if it’s worked by slamming down on the fake hand.
2 - Working in a mirror
Have you ever tried this? Looking only in a mirror (block your direct view of your hand), try writing your name. Pretty disorientating when your sight doesn’t match what you feel, right?
3 - Extra finger
Try this to give someone the sensation of having six fingers! Set up the participant in front of a mirror like this, and ask them to look at their hand in the mirror. Stroke their fingers, one by one, from the knuckle to the fingernail, on matching digits of each hand, counting each finger as you go. Repeat it again, but this time, on the concealed hand stroke the inside of the little finger on ‘5’, and then add a sixth stroke, stroking top of the concealed hand’s little finger and thin air next to the visible hand. They should feel like they have a sixth digit!
4 - Double nose
This is a simple one, showing the confusion that can be caused when different parts of our bodies feel different things. Cross your fingers like this, and stroke them across your nose. Because the outside edge of your fingers are touching the nose, it might feel like you have two noses!
5 - Confused fingers
Have your participant stick their arms out, cross them over, interlink and pull them towards themselevs, like this. Then, point at a particular finger - they’ll find it hard to move the finger you pointed at because of the tangle.
6 - Cutaneous rabbit
Test how closely we can feel sensations. Get someone to stick their arm out, then tap them like this: four times at the wrist, 3 times at the elbow, and twice higher up. If you do it consistently, they might feel like the taps were all equally spaced up the arm, not in three distinct spots!
7 - Through the floor
This will give the impression that your arms are sinking through the floor. Get your participant to lie down on the floor with their arms straight out and eyes closed. Pull their arms by the wrists and hold them up for about a minute, then very slowly lower them back to the floor. As you slowly drop them, ask what they feel.
8 - Heavy boxes
Get two boxes that weigh about the same, but are different sizes, and put the same weight in each one. Ask people which is the heavier box. They’ll tend to guess the smaller one, although they actually weigh the same, because their expectation is that the small one should be lighter, so their perception of it’s surprising weight is exaggerated.