You don't say? Does that tickle?

Ever wonder why people are ticklish? If so, you're not alone. Great minds such as Aristotle, Sigmund Freud, and Charles Darwin also have pondered the subject. Yet no one knows for sure.Ticklishness fa

Ever wonder why people are ticklish? If so, you're not alone. Great minds such as Aristotle, Sigmund Freud, and Charles Darwin also have pondered the subject. Yet no one knows for sure.

Ticklishness falls into one of two categories: gargalesis (the kind that makes you laugh and squirm) and knismesis (the disconcerting or itchy sensation like a feather brushing lightly over your skin, also known as light-touch tickling).

There are some ideas about why the laughing kind of ticklishness occurs:

It's a way humans bond. When a mom tickles her baby, the baby laughs, the mom smiles, and they share a happy moment. Similarly, kids who enjoy tickling each other may bond over the experience. (Then again, tickling can be a form of bullying.) Among adults, tickling can be a kind of sexual foreplay. (However, some people hate to be tickled and view it as painful.)

Ticklishness protects vulnerable areas. The top ticklish spots are around the armpit and the abdomen, and it's thought that our reaction to tickling here is a protective reflex. However, there are some holes in this theory, since the hands and face are more vulnerable, but they are not particularly ticklish.

The feeling that comes from light-touch tickling may be another type of protective reaction, as it makes you want to rub the area. So, if you feel a bug crawling on you, the impulse from its light-touch tickling is to brush it off and thus stop it from causing any harm.

Why can't you tickle yourself? Once again, there are no convincing data. But one idea is that laughter-associated tickling requires that you not know it's coming. Studies show that people laugh more when they're blindfolded and don't know where or when they'll be tickled.