Ever wonder why people are ticklish? If so, you’re in not alone—great writers and thinkers, including Aristotle, Sigmund Freud and Charles Darwin have pondered the subject. But they were not able to answer the question.
In fact, so far, no one has—but that’s not to say people aren’t studying it. While there’s not a lot that’s definitively known about tickling, there’s more research on the subject than I’d expected.
Tickle researchers (yes, there are people who do this for a living!) separate tickling into two distinct categories:
1. Gargalesis is the kind of tickling that makes you laugh and squirm (Let’s call this laughter-associated tickling.)
2. Knismesis is the kind of tickling you experience when you run your fingernails or a feather lightly over your skin—or, as a creepier example, imagine the feeling of a spider crawling up your leg. It’s probably not something that would make you laugh. (We’ll call this light-touch tickling.)
Researchers also note that the laughter that comes with tickling seems to be different than the laughter that comes from watching a funny movie. For example, there’s a “warm up” effect with humorous laughter—if you hear several jokes in a row, the later ones may seem funnier than the first because the first jokes got you warmed up.
The same is not true with ticklish laughter. One study found that people didn’t laugh harder when being tickled after watching a funny movie than people who had not watched the movie. One prominent tickle researcher, Christine Harris, Ph.D., compared this idea to the fact that crying from cutting an onion and crying at a funeral are very different states.
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