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Whether it’s your armpits, ribs or soles of your feet, the experience of ticklishness is common to almost every person on Earth.
Research is yet to deliver a satisfying answer as to what causes this funny phenomenon.
Gargalesis and knismesis, the technical terms, have puzzled thinkers like Aristotle, Galileo and Darwin for millennia.
Nobody has been able to solve some of the most enigmatic questions: Why are we ticklish? Why are certain body parts more ticklish than others? Why can’t we tickle ourselves? Why do some enjoy being tickled while others despise it?
Caption: Babies often love being tickled.
Credit: Kyle Flood CC BY-SA 2.0/Wikimedia Commons
What do we agree about?
Two types of ticklishness have been nailed down.
Gargalesis is the hard stuff. A hand jammed in the ribs or fingers pressed in an armpit.
It’s the tickling that makes us squirm and scream and cackle like hyenas. It also seems to only occur in certain areas of the body.
Children might love it, whereas most adults will avoid it like a parking fine.
However, there are serious ‘professionals’ who tie themselves up and partake in competitive endurance tickling worth huge sums of prize money.
Knismesis is the gentler variety. It can be elicited almost anywhere on the body, by the tip of a feather or the microscopic feet of an ant.
According to certain pockets of the new-age wellness space, it’s a mode of therapy.
It seems that context and consent is crucial, though. Both varieties have been used as forms of torture by corrupt regimes for centuries.
Caption: According to legend, ‘goat’s tongue’ was a form of torture that supposedly involved soaking the victims feet in salt and allowing a goat to lick them clean
Credit: Nan Palmero/Rothenburg Germany Torture Museum CC BY 2.0/Wikimedia Commons
Brain chains
In neuroscience, the two types can be clearly distinguished.
Gargalesis leads to a firing of neurons in many different areas of the brain. A reaction can occur in as little as 300 milliseconds.
A similar reaction has been measured in other primates, like bonobos, gorillas and chimpanzees. In a lab setting, rats are useful subjects. The rodents love to be tickled on the napes of their necks.
Knismesis, unsurprisingly, is more subtle. It only lights up a few of the same neural pathways as gargalesis and does not have the same proliferation in motor-related areas.
A laughing matter
Dr Shimpei Ishiyama, a neurobiologist at the German Central Institute of Mental Health, is focused on the positive science of playfulness and fun.
“This ‘why’ question is always difficult to answer because biologists tend to associate things with adaptive function,” he says. “There must be a survival benefit.”
Some have argued that knismesis is a response to parasites, like ticks, trying to get at our warm and vulnerable spots.
Whereas gargalesis is often argued to be a group phenomenon.
Inherently social creatures, human beings want to fit in with those around us, and maybe tickling is a result of our love for play and laughter.
“Many mammals are social animals that show this ‘play’ behaviour,” Shimpei says.
Caption: Rats, like us, often adore being tickled and will clamour for more.
Credit: Matt French/Flickr
“If you prevent ‘play’ behaviour in young rats … they have some cognitive problems or social problems later on as adults.”
Though the reasons for why these experiences evoke laughter specifically, why it occurs in even extremely young children or only in certain body parts remains elusive.
Shimpei notes that it isn’t even related to the amount of sensory fibres present.
“Fingertips are the most sensitive body parts, right? But they’re the least ticklish parts.”
He also points out that context appears to be crucial in other mammals too.
“Rats are nocturnal animals – they’re afraid of bright environments,” he says. “If I put them in an environment where they feel anxious, they don’t respond to tickling any more.”
