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In the fourth century BCE, Aristotle wrote in Parts of Animals 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.” Although this ancient theory misses the mark, it lies at the beginning of a long tradition of philosophers and scientists questioning the nature of tickling. Thinkers such as René Descartes, Baruch Spinoza, Galileo, and Charles Darwin have provided their own theories about this weird autonomic response. Yet despite 2,500 years of investigating the matter, scientists still aren’t sure why it’s impossible to tickle yourself.
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It's a fibHumans stand apart from other animals in many ways, but being ticklish isn’t one of them. Homo sapiens’ closest relatives — bonobos, chimpanzees, and gorillas — all respond to tickling. Dogs, penguins, rats, and many other animals can also be tickled (metaphorically) pink.
A few theories about the nature of tickling have grown out of this legacy of scholarship. One idea is that tickling is a form of parental bonding, while another posits that it’s a warning mechanism to protect sensitive areas of our bodies from potential injury. We’ve also learned that there are actually two types of tickling: knismesis and gargalesis. Knismesis occurs when something light brushes across your skin, which is something you can induce by yourself. However, gargalesis — that uncontrollable funny-but-not-funny tickle — can only be triggered by another person. Why? Well, basically, your brain knows a tickle is coming when you do it to yourself, which in turn suppresses its response. Evidence from brain scans shows that the somatosensory cortex and the anterior cingulate cortex, which process touch and happy things, respectively, are more stimulated when tickled by someone else compared to ourselves. The only exception to this biological rule is people with schizophrenia, because they often can’t differentiate between self and external touch. Even though tickling usually induces a smile, just remember that those “happy feelings” during a tickle are actually part of an uncontrollable defense mechanism, not genuine laughter. So please — practice safe and consensual tickling.
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A “genuine” smile with upturned lips and eye wrinkling is called a ______.
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A “genuine” smile with upturned lips and eye wrinkling is called a Duchenne smile.
The FBI considered the co-creator of Tickle Me Elmo a Unabomber suspect.
The year 1996 was a good one for Mark Johnson-Williams. The laughing toy sensation Tickle Me Elmo, which he co-created with the company Tyco, was flying off the shelves. The other bit of good news came on April 3, 1996, when Ted Kaczynski was finally apprehended after sending bombs in the mail for nearly 20 years. These two facts may seem unrelated, but not for Johnson-Williams — because in 1995, he had somehow become a potential suspect in the decades-long manhunt for the Unabomber. Johnson-Williams became a suspect mostly due to a series of amazing coincidences: For example, he lived just 22 miles from Kaczynski’s parents, he owned blueprints to a plane that the Unabomber had tried to blow up in 1978, and his hometown was Forest City, Iowa (Kaczynski signed one of his letters as “F.C.”). Other strange similarities between Johnson-Williams and the Unabomber included ties to Massachusetts-based alma maters and frequent visits to Chicago. Of course, receiving lots of mechanical parts and fuses in the mail while also sending electronic schematics for his work on toys didn’t help things for Johnson-Williams. For six months, he was frequently interviewed by the FBI, and agents even met him at his office at the toymaker LeapFrog in Berkeley, California. Once Kaczynski was captured in April 1996, Johnson-Williams breathed a sigh of relief — unaware that he was soon to play a big role in another major manhunt. Thankfully, this time the target was red, fuzzy, and ticklish.
Darren Orf lives in Portland, has a cat, and writes about all things science and climate. You can find his previous work at Popular Mechanics, Inverse, Gizmodo, and Paste, among others.
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