The Real Reason Only Some People Are Ticklish

Being ticklish is, well, a ticklish business. Youngsters especially wriggle and giggle after the slightest brush against their toes or tummies while others react with a shrug or look annoyed. "As with any sensory experience, people have different levels of sensitivity to touch and tickle," says Alicia Walf, Ph.D., a senior lecturer in cognitive science at Rensselaer Polytechnic Institute in Troy, New York (via The Healthy).

There are a couple of reasons why people are ticklish — and there are different types of tickling, too. One is knismesis, which occurs when a light irritation (like an ant crawling on your arm) triggers the urge to brush it off. You actually can tickle yourself this way with a fast, feathery touch (via Medical News Today).

The other type is gargalesis, which is when you laugh once someone touches a sensitive spot like the neck, sides, armpits, feet, and stomach. Some research indicates that this type of tickling is a reflex-like response to protect these sensitive areas.

One 2013 study discovered that researchers who tickled subjects' feet, making them laugh, activated the hypothalamus, or the area of the brain responsible for involuntary responses. Basically, tickling starts a chain reaction between your brain and your sense of touch, causing reflexive giggles, Walf told The Healthy. If you have happy memories of being tickled or you're in a good mood, you might laugh in anticipation even before the tickling starts, she said.

When you're happy and being tickled, you're more likely to laugh

But tickling isn't always a laughing matter. Another study found that subjects' brains responded differently depending on whether the tickling resulted from joking around or whether the person being tickled processed it as a painful experience.

In general, people are more ticklish when someone catches them by surprise and when they're not angry or sad, other studies show. If the person doing the tickling is a trusted friend or relative, that's also more likely to generate a relaxed tickle response than a stranger, research shows.

Although scientists are studying whether some sensations such as whispering or tickling can temporarily improve depression, some people just don't like being tickled (via Healthline). To keep tickling playful, experts recommend tickling slowly and gently on the palms, the tops of the feet, and the back of the head — and stopping when someone asks, even if they're laughing.