Hack 65. Why Can’t You Tickle Yourself?
Experiments with tickling provide hints as to how the brain registers self-generated and externally generated sensations.
Most of us can identify a ticklish area on our body that, when touched by someone else, makes us laugh. Even chimpanzees, when tickled under their arms, respond with a sound equivalent to laughter; rats, too, squeal with pleasure when tickled. Tickling is a curious phenomenon, a sensation we surrender to almost like a reflex. Francis Bacon in 1677 commented that “[when tickled] men even in a grieved state of mind . . . cannot sometimes forebear laughing.” It can generate both pleasure and pain: a person being tickled might simultaneously laugh hysterically and writhe in agony. Indeed, in Roman times, continuous tickling of the feet was used as a method of torture. Charles Darwin, however, theorized that tickling is an important part of social and sexual bonding. He also noted that for tickling to be effective in making us laugh, the person doing the tickling should be someone we are familiar with, but that there should also be an element of unpredictability.
As psychoanalyst Adam Phillips commented, tickling “cannot be reproduced in the absence of another.” So, for tickling to induce its effect, there needs to be both a tickler and a ticklee. Here are a couple of experiments to try in the privacy of your own homeyou’ll need a friend, however, to play along.
6.5.1. Tickle Predicting
First, you can look at why there’s a difference between being tickled by yourself and by someone else.
6.5.1.1 In action
Try tickling yourself on the palm of your hand and notice how it feels. It might feel a little ticklish. Now, ask a friend to tickle you in the same place and note the difference. This time, it tickles much more.
6.5.1.2 How it works
When you experience a sensation or generate an action, how do you know whether it was you or someone else who caused it? After all, there is no special signal from the skin receptors to tell you that it was generated by you or by something in the environment. The sensors in your arm cannot tell who’s stimulating them. The brain solves this problem using a prediction system called a forward model. The brain’s motor system makes predictions about the consequences of a movement and uses the predictions to label sensations as self-produced or externally produced.
Taken from : Mind Hacks
