Why is it impossible to tickle yourself?

Question

Even if I know someone else is going to tickle me it still tickles, so it is not just 'the surprise factor'...

Answer 1

Have you ever tried to tickle yourself? Did you resort to brushing the tip of a feather or a thread of wool against your own foot? And it still didn't work? According to English neuroscientists, the reason it didn't work is the very same why we don't feel our shoes rubbing against our soles every step of the way: the brain blocks sensations caused by the body's own movements. Including the feeling of self-tickling.

Scientists have long believed that every order for the execution of a movement leaves a "copy" of itself circulating in the brain, as a means of informing other brain areas and preparing for the movement that is about to take place. Thanks to this copy we can perform complex movement sequences, monitor our own movements, and even recognize them as our own.


But the copy of the motor command probably has a second function: forecasting and suppressing sensations that will result from the movement itself. This would leave the brain "free" to receive unexpected, and much more informative, sensations. Thank goodness, because "self-inflicted" sensations are potentially so many, and so constant, that they could drive us nuts. Ever wonder what it would be like to feel your tongue wiggling inside your mouth with every word you say? Of course you can do that if you choose to pay attention to your tongue, but otherwise it would be just too distracting. Better let the brain worry about the unpredictable.


The proposed sensation forecasting from the internal copy of motor commands is interesting, but was not much more than a proposition until 1998 - when some serious English neuroscientists had the improbable idea of tickling their subjects.


They had several predictions to test. First, self-tickling should give but an inkling of what being tickled feels like. Duh... everybody knows that! But this is science, where "everybody knows that" is not worth much. One must test, get data, and if possible, numbers to compare. So Chris Frith and his team at the Welcome Department of Cognitive Neurology, in London, came up with a small robot to tickle people's hands, and showed them how to "grade" sensations. And, as expected, the unexpected sensations caused by the robot were rated more intense, pleasant, and ticklish than when subjects used their own fingers.


Another prediction to put to test was that the brain should be much less responsive to self-tickling than being tickled. Six subjects got into a magnetic resonance machine (one at a time, of course!), and had their brain activity scanned as they used a gadget to tickle their own hands. This funny-looking box had a lever that, when pushed with a finger, moved a small sponge that brushed the palm of the other hand. Sometimes the subject operated the lever himself, trying to self-tickle; at other times, the researchers did it from outside the machine.


Indeed, the response of the somatosensory cortex, that brain region that feels touches to the skin, was much larger when the researchers did the tickling. If subjects controlled the sponge, producing exactly the same stimulation, there was much less activation of the somatosensory cortex. And if there is less activation, it should follow that sensation is dampened. Just like they expected: the brain does not respond as well when stimulation comes from itself.


And how does the brain know it's trying to tickle itself? The response lies just above the nape, in the cerebellum, the posteriormost part of the brain. Exactly what the cerebellum does is still a cause of heated debate, but it certainly works, among other things, to coordinate movements to the senses. Touching a finger to your nose, for instance, is one of the oldest ways to check if your cerebellum is o.k. - if it's not, your finger will move erratically until it lands, instead of moving on a smooth, straight line.


So researchers propose that it is the cerebellum who forecasts what sensations will result from movements, working more or less as a "detector of unforeseen sensations." When sensations don't match the prediction, it "goes off", and sends a signal to the somatosensory cortex that enables responding to the stimulus. But when sensations match the prediction, it does not go off - and not much happens in the cortex.


This is just what Frith and colleagues found. Tickles coming "from the outside" are caught by the detector and activate the cerebellum, while self-made tickles match the forecast and come up to... nothing special.


If the difference is in the prediction, fooling it must be a way of upgrading self-tickling. And Frith's volunteers managed to do it by tickling themselves by remote-control (bet you never thought this kind of thing went on in scientific labs!). Instead of tickling one hand with the other, movements made with the left hand were transmitted to the right, via robot, by remote control. As usual, it wasn't very ticklish. But occasionally the remote control lagged a bit before passing on the command, to wait for the prediction to "go away". And the longer the lag, the stronger they managed to tickle themselves!


Great: ticklish sensations are those that the cerebellum cannot predict. But how to explain the rolling laughter of children and the tumbling defenses of even the toughest guy at the mere sight of wiggling fingers poised ready to strike?


Now it was a group of Swedish scientists who got their turn tickling volunteers. Or rather, threatening to tickle. Martin Ingvar, one of the pioneers of the resonance imaging technique, compared the brain response to tickles and to the anticipation of tickles. Both work the same, activating the somatosensory cortex just as much. For the brain, the threat of a tickle feels just like the real thing.


But science has yet to explain why some touches feel like touches, and others feel ticklish. What makes the difference: intensity? The repetitions in tickling? The body part struck? Research volunteers still have to laugh some more...


Now for the last detail. And for the most ticklish among readers, a hope. Activation in the somatosensory cortex is attenuated by any movement you do. In Frith's experiment, moving the lever, even if the sponge was not there anymore, still deactivated the cortex.


If all this is true, there may just be a remedy against tickling: striking back tickling yourself, on the very same spot, at the very same time.


The only problem is that I have yet to find a willing volunteer. I tried to test this revolutionary method to provide the reader with a tried-and-true recipe, but my husband, whose feet would provide the perfect test, didn't really appreciate the idea. Would somebody like to try? Send your results to the author and join the Revolutionary Anti-Tickle Method's First World Test Volunteers' Club!

Answer 2

I think to be tickled, 2 things have to be true.

First to have to basically trust the person tickling you. For example, you can't easily be tickled by someone you are afraid of or a complete stranger.

Second, there has to be some kind of uncertainty about what is going to happen. This generates the excitement.

For the same reasons, you can't tickle yourself (no uncertainty). You might be able to feel a tickling sensation using a feather say. But you are not going to be rolling around with laughter.

Answer 3

It seems to be 'not just the surprise factor' but really it is. The mind is NEVER in the present. And so the intelligence at the cellular level is EVER surprised when someone else tickles us ! Hold that somebody's finger and ask him to allow you to tickle with his finger, if he does not interfere (surrendering his finger), still it will not tickle ! It is not just about tickle alone, even injecting a needle, slapping, etc is also perceived only as a surprise, and the body IS surprised, with appropriate responses !

Answer 4

.
very simply put, because you cannot suprise yourself
with touch, there is always foreknowledge of the exact
spot you are going to touch therefore you expect the
sensation.

With other touching you there is a recognition but
the mind / body is not in control of the exact location
and so cannot prepare its resopnse in the same way.

There is an emotional aspect of this that involves
expectations but I havnt time to go into it, mentioning
it here may entice someone to give a description of the
phenonema for you or you could search it for yourself,
try something like Emotional implications of tickling and
pain, hope of some small help ... :-) ...

Answer 5

It's not that it doesn't tickle, but that self-tickle is less tickly than external-tickles. This isn't the case for schizophrenics though who experience self-tickle to be as tickly as externally generated tickles. Also, if you self-tickle after having a dream it can be as tickly as external tickles. This is believed to be because schizophrenics and waking from a dream leads to problems in monitoring where the tickle is coming from. After a dream you mistakenly believe that the tickle is from someone else

Answer 6

it's not impossibl to tickle one's self. you can tickle yourself on your top palate. The reason it's not easy to tickle ones self is because you know what's coming. You expect it and this takes away the unexpectedness which is what allows us to be tickled. which is also why you often get the sensation of tickling yourself when you apply cream as you're not actually trying to tickle yourself so it's unexpected.

Answer 7

That must make me a weirdo then, because I can!!
I can't touch my neck or feet, no one can Its too much, I cant stand it. Washing my feet in the bath is F*****up. You should see it. No you shouldn't see it. l lie
Check this out!! If I see someone else being tickled (neck) I feel it. mad I know, I live it

Answer 8

That may be becoz tickling involves the touch and feeling of another person, but u can tickle ur feet with ur own hand.

Answer 9

Because your brain tells your fingers exactly how to move, so the nerves know to expect where to feel the sensation. When someone else tickles you your nerves are responding very quickly and cant anticipate the sensation which is why it feels weird.

Answer 10

It isn't impossible. I accidentally tickle myself all the time. Like when when I rub cream on my feet...

Answer 11

AHA!

If you watched a particular episode of 'Braniac, science abuse'. It showed us that there was one place on the human body where we could tickle ourselves.

Touch the roof of your mouth gently with your finger (At this point I can see the entire Yahoo Community with there fingers stuck in their mouths. Lol).