Why do we laugh when tickled?

What did the buffalo say to his son, when he was leaving for college?

Bison!

While jokes like these do ‘tickle our funny bones,’ did you ever wonder about the phrase in itself? As in, why is it ‘tickling’ the funny bone and not just touching it? Consequently, an even better question to ask would be: Why do we laugh when tickled?

Tickling has such a history that the Greek philosopher Aristotle wrote about it in 350 BC. He stated that “The fact that human beings only are susceptible to tickling is due:

1) to the fineness of their skin and,

2) to their being the only creatures that laugh.”

While that doesn’t stand entirely true today, as research suggests that apes and rats too can laugh. Yet there’s still a lot of mystery around tickles. But many scientists have actually delved into the topic. Here’s what we know:

What is tickling?

Even after so many centuries since the existence of Aristotle, there’s no one definition for tickling. According to Glenn Weisfeld, a psychologist who studied human emotions and tickling, ‘it’s a sensation you get either when something mildly moves across your skin, or when someone attacks you in a vulnerable place for fun’. 

There are different kinds of tickles

Beneath your skin lay millions of tiny nerve endings that alert the brain to all types of touch. It’s this sense that prevents us from, burning our hands when we put it on a hot cup of tea or whether we should put on a sweater when it’s cold outside. Scientists speculate that the feeling of being tickled comes when the skin cells are telling us we are feeling pain and touch together.

Two types of feelings that are described as a “tickle”. Their scientific names are “knismesis” and “gargalesis”.

1) Knismesis occurs from a light touch, like a feather touching you, and can happen on the skin anywhere on the body. This type is also seen in cats, dogs, and lots of other mammals.

2) Gargalesis occurs from a heavier touch to “ticklish” parts of the body (like the tummy, underarms, and the soles of the feet). This can make us laugh even if we don’t want to. This response also happens in apes.

Parts of our brain that respond to tickling

When the nerve endings in our skin are lightly stimulated: for example, by another person’s fingers or by a feather, they send a message through your nervous system to your brain. The brain then analyzes the message. The effect of a light touch that results in a tickling sensation is the result of the analysis of two regions of the brain. The somatosensory cortex is responsible for analyzing touch. The signal sent from the skin’s sensory receptors also passes through the anterior cingulate cortex, which governs pleasant feelings. Together, these two regions create the sensation of being tickled. This sensation seemingly results from a light touch. As anyone who’s ever been tickled too hard can attest, too much pressure can cause tickling to go from pleasurable to painful.

Our brain has to deal with a lot of information coming in all the time. When that touch is from another person or thing, this is important to know. It could be a spider crawling on you! The knismesis, feather-touch type of tickle might be part of our system for determining when some foreign object is touching us.

Some researchers think gargalesis, the heavy tickle, might help us learn to fight. The laughing from tickling encourages the tickler to keep going. While the person being tickled tries to protect the ticklish parts of the body. It could be something like a reflex – just like when there’s a loud unexpected noise like a balloon popping near your face. You can’t help being startled.

Why some people are ticklish and others are not, and why people have different ticklish spots is still a mystery! But as long as there are older siblings, prankster uncles and sneaky friends around,  it would be safe to assume that this informal experimentation will continue unabated!

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