From wild cheetahs and cougars to the tiniest little fuzzball, just about all cats can purr – and, just like the wag of a dog’s tail, it’s an unmistakable signal that everything in that kitty’s life is A-OK right now. Or is it?
As it turns out, this most ubiquitous of feline noises is way more mysterious than you might imagine. We don’t even know for sure how the noise is made, let alone why, or what it means. Add to that the strange effects this diminutive rumble has on both the cats and their owners, and purring is a phenomenon that has long puzzled scientists.
First things first: it doesn’t always mean a cat is happy.
Why do cats purr?
It’s probably the first – maybe the only – piece of unambiguous cat communication we learn as humans: a purring cat is a happy cat. That’s definitely true – sometimes.
Assuming it’s always the case would be a mistake, Tony Buffington, a cat expert and veterinarian at Ohio State University, told Wired back in 2015: “All behavior depends on history, context and expectation,” he explained. “It's naive to think that cats can only purr for one reason – it's like thinking that people can only laugh for one reason.”
Just like we may laugh to ease tension or out of surprise, a cat’s purr can convey a wide range of emotions. It may most often indicate contentedness, but not always: sometimes it signals nervousness or fear; other times it’s a sign of stress.
“I’ve witnessed a lot of cats purring when they’re dying, and when they’re being put to sleep,” cat behaviorist and photographer Marjan Debevere told BBC Future in 2018. “The vet will say something like ‘They were purring right up until the end’, and people assume they’re happy when they’re purring. That’s just not always the case.”
In other words, purring on its own can mean, well, just about anything. In fact, the first purr a kitten makes, at only a few days old, has nothing to do with happiness at all – it’s actually more of a homing beacon, so their mama cat can find them for feeding time. For some kitties, that purr stays with them for life: “Researchers have recorded ‘ordinary purrs’ and purrs that were soliciting food from their owners,” author and cat behavioral expert Celia Haddon told the BBC.
Part of the problem with deciphering this happy hum is that, unlike dogs, cats have been relatively ignored in the study of animal communication and behavior. Researchers report much more interest in canine behavioral studies than feline – a discrepancy which, to a certain extent, just comes down to practical reasons, like dogs’ natural obedience versus cats’... well, not that.
Equally, though, experts point to our different expectations for cats as compared to dogs. As a general rule, we don’t expect cats to be affectionate or talkative – and let’s face it, a scared or angry pet kittycat is generally easier to deal with than a panicking Doberman – so there’s historically not been much motivation for trying to figure out what they’ve been telling us.
That’s started to change, but only recently: “We’re just beginning to understand it,” Gary Weitzman, a veterinarian and CEO of the San Diego Humane Society, told the BBC, “and there are more unanswered questions than answered.”
Some of the most intriguing of those questions don’t relate to your cat’s emotional state at all. “In the early 2000s we hypothesized that purring has other purposes besides [communication],” Weitzman said. “It’s likely that purring has communication, appeasement, and healing properties.”
The Healing Power of a Purr
Yes, you read that right: a purr may actually have healing properties. The frequency of the vibrations that cause the tell-tale sound range from around 20Hz up to 150Hz – and “Purr frequencies correspond to vibrational/electrical frequencies used in treatment for bone growth/fractures, pain, edema, muscle growth/strain, joint flexibility, dyspnea, and wounds,” as one 2001 paper pointed out.
It’s not as far-fetched as it sounds. While studies haven’t yet confirmed the effect in cats, we do know that low-intensity vibrations can promote the growth of connective tissue and blood vessels in injured mice, and other studies have shown that vibrational therapies at frequencies of around 30Hz can improve bone density in humans.
That’s led some researchers to suggest that your kitty’s contented purr may double up as a sort of self-therapy after injuries or stress. It’s not something you’ll read in the scientific literature, but some cat enthusiasts will even tell you they’ve seen their fuzzballs using this “purr therapy” for their pals, rumbling out those magic frequencies into an injured companion.
Evolutionarily speaking, it’s ingenious. Cats can easily spend up to 18 hours a day asleep, only occasionally getting up for a manic half hour or so of zooming around murdering small toys and critters – and as it turns out, that’s probably not the best routine for promoting bone and muscle health. With purring, the animals may have figured out a way to cheat leg day, so to speak: the vibrations humming through their little bodies are acting as a low-energy, unconscious way to stave off brittle bones and weakened tissues from their mostly-sedentary lives.
The Master Manipulation of a Purr
So, there’s clearly more to a cat’s purr than meets the eye – or, uh, ear. But as it turns out, the therapeutic effects of the sound go even deeper than the physical: “I think the purr has a big benefit for humans,” Weitzman said. “The physiological benefits aside, we’ve always responded to purring’s psychological effects. It calms us and pleases us, like watching waves against a beach.”
So relaxing – and, perhaps, vibrationally advantageous – is the feeling of petting a happy purring cat that living with one of the little furmonsters has been shown to radically reduce your risk of death from a heart attack or disease. It’s not an effect of pet ownership alone, either: no such benefit was shown from having a (famously non-purring) dog, for example.
Don’t think, though, that your kitty is purring in your lap purely out of the goodness of their own heart. Cats have long proven themselves something of an evil genius species – who else would purposefully pitch their meows to match the sound of a crying baby just to better attract their owner’s attention? – and it turns out their purrs are no exception to the rule.
“In the morning loud purring can be used, together with human face patting or rubbing, to wake up a human and thus get breakfast,” Haddon pointed out. “Most of us feed the cat before ourselves, which shows how effective their communication is.”
And just what makes their purrs so irresistible is particularly sneaky: when a cat wants something from us, it can embed an unusually high-frequency call into the normally low-pitched rumble. It’s kind of like an aural subliminal advertising: “The embedding of a cry within a call that we normally associate with contentment is quite a subtle means of eliciting a response,” University of Sussex Professor of Animal Behavior and Cognition Karen McComb told BBC Science Focus Magazine, and "purring is probably more acceptable to humans than overt meowing.”
If you’re feeling hurt or betrayed by that information, however, just know this: cats may use their purrs to manipulate our emotions and bend our behavior to their will, but we love them for it. “We respond to a cat’s purr as a calming stimulus and may have even genetically selected cats with more propensity to purr,” Weitzman said.
In other words: you asked for it, sucker. There’s just no fighting the purr of a happy cat – so why even try? Bow to your furry overlords, puny human!
All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.