What do you think of this fact?
Tickling is actually a strange feeling. It’s a touch that should be unpleasant, and yet we laugh. It turns out we’re not the only ones. Rats do it too.
A laugh above your hearing range
According to NPR, when rats enjoy being tickled, they make high-pitched squeaks that humans normally can’t hear because they are ultrasonic. The idea that this is a kind of laughter goes back to brain researcher Jaak Panksepp. According to National Geographic, he and his colleague Jeffrey Burgdorf studied it years earlier. Panksepp thinks ticklishness may have evolved to encourage play.
In 2016, Shimpei Ishiyama and Michael Brecht of Humboldt University in Berlin went a step further. They tickled rats while measuring activity in their brains. The study was published in the journal Science.
Joy jumps in the lab
The rats reacted like little kids. They squeaked, and according to National Geographic, they even did “Freudensprünge” after being tickled, German for joy jumps. The researchers borrowed the German word, and English-language media use it too. According to NPR, the animals even sought out the hand again instead of running away from it.
In the brain, Ishiyama and Brecht found the area responsible in the somatosensory cortex, the region that processes touch, specifically in the part that handles the trunk of the body.
Bonus fact: According to National Geographic, the ticklishness disappeared when the rats were stressed, for example under bright light or on a raised platform.
Why it matters
Maybe you know the feeling: when you’re in a bad mood, tickling is more annoying than funny. According to NPR, Ishiyama calls tickling “very mysterious”. But the study shows it is closely tied to play and mood, and that it isn’t just a human thing.
Panksepp summed it up for NPR: “Children love to be tickled.” Rats apparently do too.
Somewhere in a lab in Berlin, a rat is giggling right now, and nobody can hear it.