Lab Notes: Why are we ticklish?

Now, being tickled is sort of fun but sort of torture, and it seems to me kind of hard to define precisely.

How do scientists describe ticklishness?

So there's two forms of what we might call a tickle.

Uh, one is knismesis, which is that kind of featherlight feeling, and you can actually do it to yourself, that feeling that, of an insect crawling on your skin that you want to get off.

And that's kind of a different category from what you might be thinking about when you're thinking about that strong, laughter-inducing, uncontrollable, convulse, try and escape kind of, uh, tickle, which is known as gargalesis.

Gargalesis.

Isn't that a great word? [laughs]

That's an amazing name.

So this sort of feeling is one that usually most people can't give themselves, probably because when you start to move your fingers or set yourself up to tickle, then y- the motor program in your brain is saying, "I'm about to move my hand" and you're anticipating, so it's not surprising, and it's a, a different sensation.

You're getting the, the messages from both sides.

So that sort of gargalesis strong laughter inducing tends to need to be by someone else.

Does that point towards what a scientific definition of that gargalesis might be, that it's a feeling imposed externally on you that kind of makes you want to laugh? What's this, what's the definition, Anina?

You, you've kind of encapsulated all they've got.

So in this field really as far as I can work out, the definition of a tickle in this gargalesis sense is a strong laughter-inducing sensation that's different from usual touch and typically evokes a feeling of, you know, wanting to get away.

So a bit of a, an escape reflex, some convulsing.

The laughter is a, a, is the most common reaction, and [laughs] people typically end up trying to then tickle the, the tickler.

That sounds pretty familiar from my, uh, home life with a [laughs] two and a five-year-old.

Is it valid that you can kind of steel yourself and get through without it really feeling like being tickled? Is there any evidence behind that? [laughs]

I think the thing that happens when we're doing that encompasses the way that we process sensory information in general, right? So there's the incoming sensory information, and then there's the interpretation by the brain, which is huge.

The co- the component of our sensation and experience that is based on your brain having its best guess at what's about to happen is, is a lot.

So I suspect what's happening when you're bracing yourself for being tickled is you're predicting.

You're predicting the sensation.

You're trying to take away the emotional extra response so that it's literally just the physical sensation.