The Science of Purring

The entrance to the larynx, viewed from behind.

Image via Wikipedia - The entrance to the larynx

My kittens are the princes of purring. They’ll purr for just about no reason at all. One will pad their way on to my lap or lay pretty much on my face and start humming. Usually, it just makes me sleepy but their may be some benefits for me thanks to my kitties purring.

Scientists postulate that the sound is produced by rhythmic contractions of the larynx and diaphragm. “The rhythmic contractions of the muscles and vocal chords open and close the glottis. As the cat breathes in and out, air hits the vibrating larynx muscles in the throat producing the purring sound” (#1). The frequency of purring is between 25 and 150 Hertz. This range has shown signs of improving bone density and promoting healing (#2). This comfort factor may be why cats purr during stressful situations such as a visit to the vet or giving birth.

All cats purr, including big cats like jaguars and tigers. Here’s a cheetah purring in case you don’t believe me:

Unlike domestic cats, who purr during inhalation and exhalation, large cats only purr while exhaling. “Purring” has also been used to describe “sounds made by civets, mongoose, genets, bears, badgers, hyenas, rabbits, squirrels, guinea pigs, tapirs, ring-tailed lemurs, elephants, raccoons, and even gorillas when they eat” (#1).

-Questions-

  • Are cats used in a therapeutic sense for osteoporosis patients? Perhaps that solves the mystery of the “cat lady” as opposed to the “dog lady” (ignoring the factor of easier care). – This would assume a great deal of benefit from the frequency and not just a trivial amount.
  • What is triggered in the body in terms of promoting healing?

Sources:

  1. ABC Science
  2. Scientific American
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