For a cat lover, one of the most pleasant sounds is when your feline friend lightly scratches you behind the ears. Various myths have arisen around this sound that attempt to explain why it is produced and is even said to have healing effects on humans. The real mystery for the scientific community, however, is how cats produce this purr. A recent study published in Current Biology may finally…
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For a cat lover, one of the most pleasant sounds is when your feline friend lightly scratches you behind the ears. Various myths have arisen around this sound that attempt to explain why it is produced and is even said to have healing effects on humans. The real mystery for the scientific community, however, is how cats produce this purr. A recent study published in Current Biology may finally have the answer: It’s more like snoring than a random muscle spasm.
While large cats such as lions and tigers are capable of loud roars, domestic cats can only produce low-frequency purrs. Researchers have wondered how they manage to produce the vocalizations, typically between 20 and 30 hertz (Hz), that are involved in purring. These animals are small, most weighing about 10 pounds, and these frequencies are typically only seen in large species like elephants, which have much longer vocal cords. Only raccoons produce a similar humming sound, although they are unable to do so with the variation in intensity that domestic cats produce.
According to research by Christian Herbst of the University of Vienna, Austria, purring appears to come from “pads” embedded in the vocal cords of domestic cats, which create an extra layer of fatty tissue while causing them to vibrate. low frequencies. The larynx does not appear to require stimulation from the brain to produce this purr.
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Most sounds that mammals make, including cats’ meows, are produced in a similar way: a signal from the brain causes the vocal cords to compress, and the flow of air through the larynx causes the vocal cords to collide. Yes, hundreds of times per second, resulting in a collision sound. This process, called self-sustaining oscillation, is a passive phenomenon: once the vocal folds begin to vibrate, no further neural information is required to keep them functioning. However, some scientists believed that purring was something different.
The so-called active muscle contraction hypothesis suggests that domestic cats actively tense and relax their larynx muscles about 30 times per second to purr. The idea, based on measurements of electrical activity in the laryngeal muscles of purring cats, caught on and has since become a common explanation for cats’ purring.
But the new study calls this into question. The team found that cyclic muscle contractions are not necessary to produce purring. For this research, scientists removed the larynxes of eight domestic cats dying of incurable diseases: they brought their vocal cords together and pumped warm air through them. By isolating the larynx in this way, they ensured that every sound was produced without muscle contractions or neural order. The team managed to produce purring in all larynxes without active neural control, suggesting that purring does not necessarily require muscle contractions.
Herbst and his colleagues suspect that the key to purring lies in the unusual collections of fibrous tissue they call “pads.” Anatomists had previously discovered this, but its function was not known. It’s possible that these increase the density of the vocal cords, causing them to vibrate more slowly and allowing cats to produce low-frequency sounds despite their relatively small size, Herbst explained to the journal Science. Anatomically, the process works similarly to the vibration that is sometimes added to the end of words in human language.
However, the scientific community is not entirely convinced. David Rice, a biomechanics engineer at Tulane University consulted by Science, believes there is no guarantee that the vocal cords of living cats will behave the same as those of cats whose vocal cords were surgically removed for the study. Looking at distant larynxes is “kind of like removing the mouthpiece of a wind instrument and analyzing whether it sounds isolated.” The same authors, for their part, admit that the intervention of the muscle contraction process in vibration is not excluded, but assure that not claimed can be determined that this is the only cause of the purring.
Around 600 million cats live with people worldwide. They are very popular pets due to their ability to form emotional bonds and communicate with people. Additionally, this species has the most complex vocal repertoire of any carnivore. Their purring is precisely a means of communication: they are born with the innate ability to do so and usually begin to emit it from 15 days of age.
Although science has not yet fully deciphered why cats vibrate under certain circumstances, there are certain hypotheses. The kittens purr so their mother can find them; This causes them to produce serotonin, which makes them resemble human smiles and can even promote the healing of their wounds. The truth is that each cat has its own personality, as there are some that do not purr, just as some meow more than others or are less affectionate and sociable.
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