There are two kinds of tickles. Knismesis is a soft, gentle kind of tickling, such as when an insect crawls across your skin, or someone strokes you with a feather. But here we’re talking about the other kind. It’s called gargalesis and is the full-on, go-for-the-ribs or armpits tickling that makes you laugh out loud and wiggle and squirm.

Stop and think about it for a minute, and you’ll notice something very odd about tickling. When you’re being tickled, you laugh, sometimes a lot. That’s a sign of happiness and joy, right? But you also squirm and try to get away from the tickler. You might even push them away or beg them to stop, even as you erupt into yet more spasms of giggles and shrieks. What gives? Is this fun or not? 

Sure, we laugh when we’re tickled, but it’s very different from the kind of laughter that follows hearing a joke or seeing a funny meme, explains Alicia Walf, a neuroscientist at Rensselaer Polytechnic Institute. Those experiences are processed in the frontal lobe, where memory and abstract thought are processed.

The sensation of being tickled, however, is processed in the limbic system, the part of the brain involved in emotions. Those emotions can be either negative or positive, explains Walf, but they’re very basic. The limbic system is the oldest part of the brain, the seat of the “fight or flight” response.

Why are we Ticklish?

Even though scientists know what happens in the brain when we’re tickled, it’s still something of a mystery why we have this response in the first place. One of the most common theories is that tickling is a form of social bonding. Walf points out that, generally, we don’t like to be tickled by strangers. 

Tickling may play a developmental role as well. Babies and children are more ticklish than adults, and adults seem eager to tickle them. When babies are born, their sensory systems have to be trained, Walf says. By tickling our young, we may be helping train their nervous systems to distinguish between sensations that are safe and those that might become harmful. 

That could explain why we’re most ticklish around the ribs, the area near our most vulnerable organs.

“It’s good to train that area of the body to know that ‘OK, this touch is fine,” she says, “but when you go to this next level, that’s not fine.”

So, our tickle response may be a friendly way to explore and establish our boundaries. Tickle me a little and we’re having fun, but don’t go too far. If I’m a baby, I might start wailing. If I’m an adult, I might slap you. 

Robert Provine, a psychologist who studied laughter, once argued that the laughter that comes as a response to tickling might be a kind of preverbal communication between babies and their parents. Being tickled might also help an infant to gradually learn to distinguish self from other, me from mom. 

Walf, who specializes in studying stress, points out that tickling is situational.

“The same kind of touch could be processed completely differently by the brain depending on the situation,” she explains.

If you’re in a bad mood or stressed, a friendly tickle might not evoke any giggles at all. It might just be irritating. 

Read More: Do Rats Laugh? Researchers Tickled Rats to Reveal the Brain’s ‘Play Zone’

Why Can’t We Tickle Ourselves?

We react, often excessively, to being tickled by others, but most people can’t tickle themselves. This is in part because self-tickling lacks the element of surprise, according to some research. (Try asking someone to tickle you and see how that works.) But there’s a little more to it than that. 

Tickling sends a message from the body to the brain. But there’s also a descending pathway that can mute the sensation, Walf explains — for example when we’re in a bad mood or aren’t comfortable with the person who’s doing the tickling. But we always know when we’re touching ourselves.

“We have really strong body maps, so we’re controlling the sensation and muting some of the tickle pathway,” she explains. 

Not being able to tickle yourself also supports the idea that tickling is a way babies learn to distinguish self from other. Once you’ve got that down, you can’t tickle yourself.

Read More: Why We Can’t Tickle Ourselves

Article Sources

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Avery Hurt is a freelance science journalist. In addition to writing for Discover, she writes regularly for a variety of outlets, both print and online, including National Geographic, Science News Explores, Medscape, and WebMD. She’s the author of “Bullet With Your Name on It: What You Will Probably Die From and What You Can Do About It,” Clerisy Press 2007, as well as several books for young readers. Avery got her start in journalism while attending university, writing for the school newspaper and editing the student non-fiction magazine. Though she writes about all areas of science, she is particularly interested in neuroscience, the science of consciousness, and AI–interests she developed while earning a degree in philosophy.