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  • Okay, think of the last time you were physically tickled.

  • Whether it was done by a friend or family member, they were probably trying to make

  • you laugh.

  • But for most of us, especially the most ticklish among us, being tickled isn’t necessarily

  • fun, or funny.

  • So why do we laugh?

  • And where did this whole bizarre reflex come from?

  • Tickling actually refers to two different types of sensations.

  • A light tickling, like when something just barely brushes your skin and makes you want

  • to scratch or rub the area.

  • This is called Knismesis, or a moving itch.

  • And it has a helpful role: like if you have an insect on you, your response to that tickling

  • sensation can help get it off quickly and prevent a bite

  • But when we talk about tickling, were usually talking about the other sensation: where someone

  • touches you with more pressure, causing you to laugh involuntarily.

  • This is called Gargalesis, and some people are more susceptible to it than others.

  • While we don’t know exactly why, we have some ideas.

  • Most people are ticklish in areas like the neck, ribs, inner thighs, knees, or feet,

  • but these aren’t the most sensitive areas of the body.

  • If being tickled was based on sensitivity, people should be ticklish on their face, or

  • the palms of their hands.

  • Instead, our ticklish areas are the ones most vulnerable if were in a fight or being

  • attacked.

  • So, tickling may be evolution’s way of teaching even very young children to protect their

  • weak points.

  • This also explains why we can’t tickle ourselves.

  • It’s hard to attack yourself when we can predict the outcome of our own actions.

  • Being able to tickle yourself would serve no evolutionary purpose.

  • What this doesn’t tell us, is why we laugh when were tickled.

  • But think about it: imagine tickling a kid, and they start screaming and crying.

  • You’d probably stop, right?

  • But laughter is fun!

  • Scientists think the laughter response is to encourage tickling, and the self-defense

  • training that comes with it.

  • And it’s not just humans who participate in this strange activity.

  • Other great apes make a laugh-like noise when tickled, which is thought to be the evolutionary

  • precursor to human laughter.

  • But you can also tickle meerkats, owls, penguins, or rats.

  • These animals let out laugh-like noises, and most of them seem to enjoy it.

  • One study found that young rats love being tickled and will seek it out, but female rats

  • find it aversive as they get older, and will start to avoid it.

  • This behaviour sounds pretty similar to what

  • we see in humans.

  • Kids can find being tickled entertaining, but many adults don’t like being tickled

  • at all.

  • The involuntary laughter is uncomfortable, or even painful, an experience that’s supported

  • by brain scans.

  • A research group in Germany put a bunch of people in an fMRI to study the differences

  • between ticklish laughter and voluntary laughter.

  • And only ticklish laughter activated the hypothalamus, which is responsible for visceral or involuntary

  • reactions.

  • Also, ticklish laughter activated parts of the brain responsible for pain anticipation.

  • So just because youre laughing, doesn’t mean youre having a good time.

  • It turns out, the natural and common reflex to tickling is surprisingly complicated, and

  • individual opinions on the experience are surprisingly varied.

  • Are you ticklish?

  • Do you like being tickled?

  • Tell us about it in the comment section!

Okay, think of the last time you were physically tickled.


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B1 中級

なぜくすぐったいのか? (Why Are We Ticklish?)

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    PC home に公開 2021 年 01 月 14 日