Readers reply: why can’t people tickle themselves?

Read the tickle experiment done in the early 2000s by a group of psychiatrists in Glasgow (Robbie Steel was one of the main authors – he was my supervisor during part of my psych training). They demonstrated that people with schizophrenia can tickle themselves but the rest of us cannot. They invented a machine to give standardised tickles (to reduce bias in the result) at the push of a button. They asked people with schizophrenia and controls without, some of whom had other psychiatric conditions, to press the button on the machine to tickle themselves. They were able to vary the delay between pressing the button and the tickle being applied. They found that people with schizophrenia could tickle themselves, even if they were not having a relapse (were not actively psychotic) at the time. When the delay between the button press and tickle was increasedm people without schizophrenia eventually become able to self-tickle as well.

The thinking is that when we plan to do something, our frontal lobes make predictions of what is expected to happen. Data from the senses is then matched to the prediction and any discrepancies used to enable the plan to be modified to match sensory data better next time – ie, learning. As part of this process the action plan is labeled as “self derived”, and the sensory data as “externally derived”. The group postulated that in schizophrenia the labelling process can go wrong, so the brain is less able to tell what is “internal” v “external”, so thoughts can mistakenly appear to come from outside, and sensations from inside. concernedpleb

Because they don’t think it’s funny? Lucille Byrnes

When you touch yourself, there is a control loop between your hand and brain that reassures you that you are in control of the sensation. When someone or something else touches you, your brain immediately goes on alert, defence mechanisms kick in (fight or flight), and a heightened sensation results. DrBlamm0

Yes, they are called efference copies – a neural representation of the movement you have made and expected consequences of that movement. AnticitizenOne

AnticitizenOne is completely right. An intentional movement is in theory a goal-directed movement towards a type of perception, suggesting a kind of pre-activation of the anticipated consequence (the “efference copy” mentioned). The suggestion is therefore that if you know that a tactile sensation will happen by your intentional movement, this cancels out the sensation itself. None of this needs a neo-Freudian “defence mechanism” and there does not have to be any threat perception by somebody else touching you. In fact, you might notice that it’s easy to tickle loved ones (I wouldn’t try with strangers), so the “threat” part to the explanation doesn’t work and is rather redundant. Instead, there are two explanations. Either you can perfectly predict your own sequence of movements and therefore no sensation is unexpected (which is something the Glasgow group mentioned studied) or that the intention to act creates the efference copy of the perceived sensation (which is the theory favoured by proponents of ideomotor theory). The differences are slight, however, one focusing more on motor timing and the other on the intentional aspect of the action. A similar but reversed effect is sometimes seen in the ability to hear your own clapping in a crowd, despite the relatively slight amount of noise it produces and strong similarity with the clapping of other people. sovspape

If I tickle the palm of my hand very lightly, a few moments after stopping, I then have to scratch. I can’t bear the having-been-tickled sensation that persists. More generally though, I’m unticklable by others. I think I taught myself to relax into it as a child, mainly because I thought it was a neat trick to be able to pull off. Witnessing

I can – the soles of my feet are extremely sensitive (my idea of hell is a foot massage). If the questioner means why can’t we make ourselves laugh when tickled – well, it’s a very long time since I found it funny, if ever I did (when I was a child my uncle used to tickle me mercilessly, which I came to hate). Rotwatcher

You don’t laugh because you find it funny, you are forced to laugh no matter how unpleasant it is and that is exhausting. That is why it is such a bizarre phenomenon. cielosdeazul

Tickling is all about a relationship of play-acted control and play-acted fear. When you’re doing a tickling game with an infant, all you have to do is approach your hands and the kid will laugh uncontrollably. It’s because the child is safely acting out their fear, delighting in it while knowing that they will not be harmed. mjback

I can tickle myself. The soles of my feet are really sensitive, and the tickle sensation remains on my sides and feels as uncomfortable as if someone else had done it. But I guess a big part of the tickle is the surprise or anticipation, which is lost when you are controlling the action. zhage00

You can’t tickle yourself because you know when you are going to stop. The tickle response, laughter and squirming, is a minor fear of not knowing when the tickler is going to stop, which can become a major fear (for small children, especially) if the tickling persists. If you are in control of the tickling, then there is no fear response. forkevinsake

Proper tickling is I think where you can’t endure it for very long. Palms of the hand and soles of the feet are sensitive, but I wouldn’t call it self-tickling. Most people can however tickle themselves on the roof of their mouth very gently. Ernie_Bilko

When my students enter nasal swabs for quick Covid-19 self-tests, almost all of them report a sensation of being tickled. Enanti

If people could tickle themselves, the world would come to an immediate standstill. nottaken

The sensation we have of being touched as we touch a part of our own body is known as “the double sensation” in the field of phenomenology that concerns itself with the body. Maurice Merleau-Ponty, Jean-Paul Sartre and other thinkers from the mid-20th century onwards describe this phenomenon in detail through their work and vary in their analyses. What they do tend to agree on however is that it is through our bodies that we know the world, it’s not just our brain that is doing the work. The phrase most commonly used to describe this is “embodied subjectivity”. CiaranGaynor