Good Vibrations? Here's What It Means When Your Cat Purrs

We all assume, as we curl up on the couch with our feline friends, that their contended purring indicates happiness on par with what we, ourselves, are feeling at that moment. Something as simple as a scratch under the chin can elicit the most pleasing of vibrations, but what does it really mean when your cat purrs? Is this familiar sound always a sign of extreme pleasure or can it also be a sign that something might be wrong?

According to the Library of Congress, no one is certain why cats purr. There are some theories, of course, and more than a few good guesses based on quantifiable evidence. Most cats purr when they are content, when they are pleased, or when they are feeling good. Then again, some cats might also purr when they are hungry, when they’re injured, or if they are frightened. The purpose of the purr is also the subject of some debate. 

If the purr can mean so many different things, what’s the point of it? Some scientists believe that purring is a form of communication, only meant for those the cat and those nearest to it. Low-frequency vocalizations like purring are often associated with positive social situations in the animal kingdom. They are generally uttered when nursing, grooming, relaxing or generally being amiable. 

A cat’s purr uses their larynx and diaphragm muscles, both as they inhale and as they exhale. The low-frequency sound they emit, as a result, is what we call a purr. Oddly enough, we don’t yet understand how the cat’s central nervous system generates and controls those contractions. It’s something science is still working on. 

One bizarre theory indicates that purring frequencies stimulate bone regeneration, specifically in domestic cats, as reported by Futurism. This isn’t just some shot-in-the-dark theory, either. The hypothesis has been reinforced by observation. Broken cat bones typically take less time to heal than those of other animals, and cats are the only creatures among those studied that utter those same low-frequency purrs. 

Other evidence behind this hypothesis exists as well. Domestic cats purr at a frequency of about 26 Hertz, which scientists believe to be in a range that promotes tissue regeneration. If you look at the lifestyle and natural setting of house cats and their relatives, you can see that they spend a lot of time lying around, waiting to hunt. If purring does regenerate bone or stimulate bone health, it might also prevent cat bones from becoming weak or brittle in the interim. 

According to ScienceDirect, scientists are so interested in the potential regenerative value of purring that some researchers have proposed strapping vibrating plates to astronauts' feet during long space flights. The theory is that purring vibrations will help mitigate bone loss and retain bone density while the astronauts travel in low gravity. 

According to early 19th century taxonomists, purring is actually one facet of the Felidae family. This taxonomical split puts cats into two distinct lines: purrers and roarers. Purrers were cats of the Felinae subfamily and roarers tended to be subfamily Pantherinae. That theory has since changed to include most cats, with only a few exceptions. Lions, leopards, jaguars, tigers, snow leopards, and clouded leopards are all allegedly incapable of purring, whereas cheetahs and cougars can purr as gently as a house cat. 

This is entirely possible, but it also might be a form of self-soothing for kitties in stressful situations. This could explain why some cats purr when they are in pain or frightened. It’s like us humming to ourselves during an emotionally trying time. Still, if your cat is purring the moment you walk in or as you pet them, you can safely assume they like you.