laughing baby gets a tickleInteresting question. I used to be so incredibly ticklish, I would start laughing even before someone tickled me. Just the very thought of being tickled would do it. But as I got older (and the fun got sucked out of me, I guess), I grew less and less ticklish — and I’ve often wondered why that is. Before I ponder the answer to my query, though, the polite thing to do would be to answer yours, no?

There are two types of tickling, named in 1897 by the psychologist G. Stanley Hall. There is knismesis (a light tickle that does not induce laughter) and gargalesis (the heavy tickling that does induce laughter). You can reproduce knismesis by yourself but not gargalesis ... but why?

First we need to understand why we laugh so much when other people tickle us. You know those people who laugh uncontrollably in somber, serious situations? Like in a job interview, or when they’re fighting with you, or maybe at a funeral, for instance? I have firsthand experience with such people because (ahem) I am one of them. No, seriously. I was once getting yelled at in high school by the assistant principal and was so nervous that I started laughing, so uncontrollably in fact, that I hid my head in hands and pretended I was crying. The assistant principal immediately started apologizing, which made me laugh even harder. It was a mess. Needless to say, I get caught in many a sticky situation because of it — the kinds of situations that are funny only way after they’re over.

So why is it that we laugh when we’re tickled? Simply put, because of the unexpectedness of it. The cerebellum, the part of our brain that monitors our movements, can detect the difference between expected sensations (scratching an itch, for instance) and unexpected sensations (a bug landing on your ear). Because of this difference, we can’t predict where someone will tickle us or how we will feel when they do, so it makes us panic. That panic is manifested through uncontrollable laughter — sort of a more acceptable “nervous laugh,” if you will. Interestingly, this “panic mode” is thought to have been an evolutionary protection against predators. (Though I’m not sure what laughing at the snake that has just brushed up your leg is going to do.)

I therefore can’t tickle myself because if I do, it is my brain telling my hand to make those bizarre tickling motions under my arm, and since we are not surprising ourselves with the action, we do not laugh. In order to induce a laugh, there must be an element of surprise involved.

And though tickling induces laughter, it may not be the best way to get a good laugh. In fact, there are rumors of “relentless tickling” being used in ancient times (and even today, amongst some quarreling siblings) as a means of torture. That’s right, people — tickling as torture. In my opinion, if you’re looking to get a good laugh, all you really need to do is spend a few minutes cruising YouTube’s funniest videos (during your lunch break, of course), particularly this one, a classic that always brings me to giggles. After watching it, I’ll bet you’ll be positively tickled.

— Chanie

Related on MNN: 28 weird facts about the human body

Photo: jencu/Flickr
Why can't I tickle myself?
We know you've wondered about tickling. A nervous laugher explains the types and the science behind this weird body response.