Trapped between uncontrollable laughter and excruciating discomfort, it's difficult to decide when being tickled: do I like this or not? But why doesn't this happen if we tickle ourselves? New research on rats shows why.
Image: picture-alliance/Everett Collection/IFC Films
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Tickling someone else and being tickled is fun. So why isn't it fun to tickle ourselves? As new research on rats shows, there's an important factor missing when the tickling hands are your own.
Neuroscientists from Humboldt-University in Berlin have found that rats react very similarly to humans when they are tickled. When scratching or grooming themselves, for example, researchers found rats behaved differently to when they were being tickled. The part of the brain that is responsible for vocalization or laughter was inactive.
Whereas when the researchers tickled the rats, the part of their brain that recognizes sense of touch — the so-called somatosensory system — was active and the rats made a sound.
Neuroscientist Michael Brecht, a lead author of the study, said this happens because "the inhibition associated with self-touch prevents self-tickling." As the human response to tickling has been found to be quite similar, this means that we don’t associate any kind of self-touch with the sensation of tickling and therefore don’t get the same reaction as when someone else tickles us.
"If we tickle ourselves, the cerebrum (our cognitive reaction centre) interprets the sense of self-touch as non-threatening and deems it unimportant," explains psychologist Michael Titze from HumorCare in Germany.
The thrill of fear — "Nervenkitzel"
So because we are not threatening enough to ourselves, for tickling to be effective we need "Nervenkitzel" — the thrill of fear — which the tickle attack from others provides.
The rats in the study showed freezing behavior and tensed up when they voluntarily participated in tickling. Children who are tickled behave similarly. Often, their reaction to a tickle attack is contradictory, because while their laughter indicates amusement, at the same time they can’t stand the sensation and try to escape the tickler.
That’s because we associate tickling with a friendly mock-attack. "Psychologically speaking, tickling leads to interference from the opposite impulses of closeness and escape. Neurologically speaking, we feel lust and pain simultaneously which leads to tension that is released with uncontrollable laughter," says Titze.
But why do we laugh?
Sometimes, the sensation of tickling can indicate danger to our body. Especially for body parts that have the most neurons, like the stomach, armpits and groin. That’s where we are the most ticklish.
But as soon as the brain recognizes the tickle-attack as non-threatening, we release tension by laughing sometimes until we’re crying. Laughter is a natural stress reliever to restore balance and wellbeing.
Anticipatory laughter is also part of ticklishness. Even just the thought of being tickled can make us giggle. The study found that the same part of the rats’ brain that is activated when they are tickled is also stimulated when they anticipate being tickled.
Scientists think that when we laugh in anticipation in the context of a play fight, it signals a positive invitation for a play attack. So, try not to laugh next time someone intends to tickle you, and maybe they won’t discover where exactly you’re the most ticklish.
Mouths, snouts and beaks: The most bizzare mouths in the animal world
Long and pointy, wide and oddly-shaped, and sometimes monstrously large — the animal kingdom has some seriously impressive mouths. Here are some of the most fascinating.
Image: picture-alliance/blickwinkel/fotototo
Long and pointy
The sword-billed hummingbird’s beak is longer than its body. It has the longest beak of all known hummingbird species. And it needs it! One of the bird's main sources of food is nectar, which it drinks from very long, slender hanging flower crowns. With its beak wide open, it can also catch insects.
Image: picture-alliance/WILDLIFE/P.Oxford
Gobble, gobble, gobble
Two star-like shapes on its snout make the star-nosed mole a very well-equipped hunter. The appendages around its nostrils — a total of 22 fleshy tentacles — are sensory organs. With these it can examine 13 potential prey animals per second. We can't even look that fast!
Image: picture-alliance/dpa/K. Catania
Neither duck nor beaver — what are you?
An egg-laying mammal with a beaver‘s tail and a duck‘s beak. What sounds like a fantasy creature actually exists — in Australia. The platypus boasts a large, flexible beak with a leather-like surface. A built-in snorkel is also included: its nostrils are on top. This allows the animal to dive underwater and breathe at the same time.
Don't worry, as scary as it may appear, this vampire is vegetarian. The tufted deer prefers to graze at dusk. If it senses danger, it does something unusual: it barks. Deer do this to warn each other. While fleeing, they erect their white tail — an escape-signal among tufted deer.
Image: picture-alliance/blickwinkel/W. Layer
More beak than bird?
This bird may look like a character from a comic, but the shoebill actually walks among us — in the swamps of central tropical Africa. It often stands motionless in the water and looks downward. When it detects prey, it strikes at lightning speed. With the hook at the top of its beak, it grabs its prey. Even large lungfishes are swallowed up whole.
Image: picture-alliance/imageBROKER
That's one big mouth you've got
With a body length of up to 10 meters, the basking shark is the second-largest fish in the world, after the whale shark. Despite its monstrous size, it's anything but bloodthirsty; basking sharks eat just one thing: plankton. They swim with their mouths wide open to catch and filter food. Water that enters its mouth with the plankton is filtered out through its gills — 1800 tons of water per hour.
Image: gemeinfrei
A bit less ferocious than its big brother
Gavials live in Southeast Asia. In contrast to the crocodile, gavials don't eat zebras or deer, but fish. Its snout is therefore long, narrow and home to very many teeth. Perfect for catching fish!
Image: Josh More
Turbo-charging through a sea of flowers
The sucking trunk of the hummingbird hawk-moth is not only very long, it's also extremely precise. The butterfly can suck nectar from up to 100 flowers per minute. While doing so, the moth hovers in front of the flower. With its long trunk, the hummingbird hawk-moth can also reach the nectar of flowers with particularly long calyxes — out of reach for others.
Image: FARS
Just a spoonful
The spoonbill is equipped with the perfect tool. No matter fish, frog or other water-dweller, nothing escapes this beak. In searching for food. the spoonbill usually goes into shallow water. However, sometimes it also wanders the coast. In the mud flats, it swings its head back and forth, filtering food from the shallow water.
Image: picture-alliance/blickwinkel/B. Zoller
Lawn mower at the bottom of the sea
Dugongs feed on seaweed. They prefer the part of the plants that lay underground. And they have developed a special technique for this: this manatee can dig. It digs out the plant with its upper lip, then the roots are pulled out of the ground. It shakes off the dirt and then sucks the plant into its mouth.
