Life's Great Mysteries - If tickling makes us uncomfortable, why do we laugh?

Our normal response to another person tickling us is to pull away, to put an end to the discomfort. Because it really is discomfort, right? Almost like a type of pain. We squirm, we run away, we do whatever we can to put an end to it. Laughing seems like a weird response to such discomfort. We don’t laugh when we burn our finger on a hot pan, yet we pull away from a tickle as enthusiastically as we pull away from a hot pan. What’s up with the laughing? Why don’t we cry or shout instead?

I should point out that humans are not the only animals capable of laughing. Scientists have found that at least 65 other species laugh (hyenas are not one of them, by the way). And some of those also laugh when tickled.

Researchers recognize two types of tickling. Light tickling (knismesis), which is light touching with fingers or something like a feather. People can often respond to this in different ways, and they do not have to laugh. Heavy tickling (gargalesis) is intentionally touching sensitive areas like feet and armpits intending to get a reaction. When getting their feet tickled, most people have to laugh, even if they try not to. It’s involuntary. Other species of great apes also laugh when their feet get tickled.

When we get tickled, the nerve endings under the skin send signals to our brain. The anterior cingulated cortex analyzes the signals—this is the part of the brain that deals with the perception of pleasure. So, it’s important to know that your brain is interpreting the sensation as a type of pleasure (this helps explain why we respond with laughter instead of aggression).

But there’s more. The hypothalamus is the part of the brain that tells us to laugh when we are lightly tickled, but it is also the part of the brain that tells us we should expect pain when something is touching our most sensitive spots. The amalgamation of all these signals usually results in laughter.

That may explain how we end up laughing, but it doesn’t explain WHY. Evolutionary biologists and neuroscientists suggest that this response might have evolved as a defensive mechanism. Think of it this way… when a dog is intimidated by a larger dog or person, the dog will show submissive behavior, like rolling on its back to expose its vulnerable belly. This serves to signal that the dog is not being aggressive and is not looking for a fight, and therefore this behavior often prevents escalation. Well, the same idea could be true for laughing when being tickled. Laughing signals that we are not angry, that we are not the aggressor. Contributing to this is the fact that we know tickling is typically something people do out of fun, rather than as an attack, and therefore we do not need to do something more aggressive than laugh.

And this helps explain why we don’t laugh when we tickle ourselves. The cerebellum of your brain knows that you are about to self-tickle, and therefore it doesn’t bother wasting energy sending signals to the other parts of your brain that would trigger a laughing response. Your brain knows there is no need for a defensive response. It knows you do not need to signal another person to show that you are not angry.

Photo Credits:
- Tickling in bed - DepositPhotos