A cat’s “solicitation purr” contains a cry, and sounds more urgent and unpleasant than a normal purr

Sadly, I haven’t owned (or rather, been owned by) a cat in a while, but those who do may recognize that there are several different kinds of purrs. The two most notable are the “solicitation purr,” in which your cat purrs urgently when it’s mealtime or it wants fusses, and the “non-solicitation purr”, in which your moggie is vibrating away in your lap or before a fire.

In a new paper in Current Biology with the nice title “The cry embedded within the purr” (reference and free download below), author Karen McComb and colleagues show that the solicitation purr contains an element absent in the “normal” (non-solicitation) purr, and that this element is judged by listeners (whether or not they own a cat) as more unpleasant and more urgent than a normal purr. Further, the added element is similar in frequency to a meow, as well as to the cry of a human baby!

What has apparently happened is that cats either learn or have evolved—these can be distinguished by looking at kittens separated from their mother at birth and raised by hand— to make their purrs sound more urgent and annoying at feeding time, which, because the humans are disturbed, get the cats fed sooner. If the “meow” element in the purr has indeed evolved, it would be through a combination of natural and artificial selection: those cats with more disturbing purrs got more food from humans and hence left more offspring. Such a combination of natural/artificial selection may, in fact, be the way that cats became domesticated in the first place.

Why do cats purr at all? They begin doing it as kittens during feeding time, which may stimulate the mother to relax and feed them. I’m also told that cats often purr when injured, and that the frequency of vibration acts to heal things like broken bones (I can’t vouch for that and can’t be arsed to look it up, but I know there was a paper.) And some cats, but not all, purr at feeding time.

The authors recorded both solicitation and normal purrs from ten cats, and played them back to 50 people. They also made sonograms of the purrs. They followed this up with a statistical analyses.

The results:

1. When both types of purrs were played at the same volume, nearly everyone, whether or not they had a cat, found the solicitation purrs significantly more urgent and less pleasant. However, the difference in reaction was stronger in those who had a cat—people who had obviously been trained.

2. The sonograms of the two types of purrs show that the solicitation purr has less of a low-frequency “pure purr” peak (extreme left in graphs below, which plot frequency of purr elements versus their loudness in decibels), but also shows a unique “voiced” peak of higher frequency 220-520 Hz (mean 380).

3. Statistical analysis showed that height of the “voiced peak” on the left was significantly associated with a greater sense of urgency and unpleasantness in the listeners.

Here are the same “solicitation” (left) and “normal” (nonsolicitation) purrs as shown in the short paper. Note the presence of the “voiced” peak on the left (arrow) and its absence on the right:

Screen Shot 2015-06-03 at 6.47.06 AM

4.  The authors then manipulated the sonograms by removing or altering the “voiced” peak. When they did that, and played the altered sonograms back to people, they perceived the altered purrs missing the peak as less urgent than purrs with the voiced peak. They didn’t, however, perceived the altered purrs as more pleasant, which the authors attribute to the reduced intensity of the “normal” purr elements in these sonograms (“lower harmonicity”).

The authors note that the voiced peak has frequencies similar to those of a human infant’s cry, which of course calls parents’ attention to the child’s needs. This, they say, might be a general mammalian sensitivity to that frequency (presumably evolved).  Surprisingly, they don’t mention that the “voiced” element might have evolved in cats, but not other domestic animals, as a way of manipulating their human owners to get out the can opener! It is of course possible to test whether there is, as the authors note, “an inherent mammalian sensitivity to such cries.” My guess is that this vocal element is cat-specific.

Here’s a cat giving a solicitation purr; you can clearly hear the high-pitched meow-like element:

Next time you feed your purring cat, see if you can hear the difference.

__________

McComb, K., A. M. Taylor, C. Wilson, and B. D. Charlton. 2015.  The cry embedded within the purr. Current Biology 19: R507-R508.

43 Comments

  1. Mary Sheumaker
    Posted June 3, 2015 at 10:13 am | Permalink

    I don’t recall my cat purring when feeding, but he has a very specific meow when his bowl is empty. His dish generally has food left in it but in the event it gets empty and is not noticed in a timely fashion he has a very clear meow that he doesn’t use at any other time. At any location in the house when he uses that cry I look at him and say, “What? Is your bowl empty? Do you need some food?” I just now realized this. 🙂 I will have to check on the purring.

    • Posted June 3, 2015 at 10:30 am | Permalink

      “Ditto.” Hadn’t noticed anything different in the purr, but Baihu makes it quite plain when it’s mealtime.

      b&

    • chris moffatt
      Posted June 3, 2015 at 1:22 pm | Permalink

      Summer-the-stripey-cat, who was bottlefed from week1, does not purr when we have a case of Empty Food Dish Syndrome (EFDS) nor does she meow. Apparently not having been brought up in a feline family she did not acquire some normal cat behaviours. But she gets her message across by sitting silently beside the food dish until it gets filled. If that doesn’t work she will come and claw silently at my arm until the dish gets filled – that can be much more annoying than the meowing of the other cats. She reserves purring for when all are in bed and she is lying across the larger part of my pillow with her whiskers tickling my face.

  2. tubby
    Posted June 3, 2015 at 10:40 am | Permalink

    Orson does purr while eating, but for his large vocabulary for meows he seems to have only one purr. When he wants food or fusses he looms. He’s very good at looming.

    He used to rarely purr at all really.

  3. Linda Grilli Calhoun
    Posted June 3, 2015 at 10:43 am | Permalink

    Training one’s humans is SUCH a full-time job. L

    • Jeffery
      Posted June 4, 2015 at 8:40 am | Permalink

      Maybe Jerry remembers “The Fabulous Furry Freak Brothers” comics from his college days- One of the “brothers”, Fat Freddy, had a cat (who’s name is Freddy Scat) whose life was the focus of many of the cartoons. In one, he’s sitting by the door going, “Me-out; prowl-now”; as his owner Freddy walks by, his cries become more insistent: “ME-OUT! ME-OUT!” Finally Freddy says, “Oh, you wanna go out, huh?” He opens the door and the cat exits, thinking, “What IS it with these humans? Don’t they understand English?”

  4. eric
    Posted June 3, 2015 at 10:44 am | Permalink

    I’m also told that cats often purr when injured, and that the frequency of vibration acts to heal things like broken bones (I can’t vouch for that and can’t be arsed to look it up, but I know there was a paper.)

    That last part seems…unlikely. But I don’t doubt the purring-while injured part, as I’ve had cats that purred in the vets office when they were simultaneously too scared to move.

    At the risk of anthropomorphizing, to me the most sensible explanation for both is that they are trying to comfort themselves when they do that. Kinda like a scared person may sing to themselves or talk incoherently or do some other nervous habit as a way of distracting themselves from a source of stress.

    • Mary Sheumaker
      Posted June 3, 2015 at 3:09 pm | Permalink

      http://www.ncbi.nlm.nih.gov/pubmed/23416966

      Hope I am linking correctly- it is an abstract of a study published 2013 Komrakova et al, “Identification of a vibration regime favorable for bone healing and muscle in estrogen-deficient rats”

      so apparently it has been studied. The self-comfort theory makes a lot of sense too.

    • Larry Smith
      Posted June 3, 2015 at 3:25 pm | Permalink

      Re: purring in the vet’s office. We had a cat that would start purring when the vet took its temperature rectally. I figured this was way for Cleo to self-soothe herself in a stressful and uncomfortable situation.

  5. JJH
    Posted June 3, 2015 at 10:59 am | Permalink

    Fascinating. The cat I work for never “purrs” when she wants something, she meows. And it doesn’t matter if what she wants is kitty treats, a door open, brushing and fusses, etc., it’s always a meow. The only time she purrs is when she is actually getting fusses or if she has already commandeered my lap even if I’m reading and not actively petting or brushing her.

    But, now that I think about it, yes those “I want something” meows are truly annoying. Well, at least now I have a scientific explanation of why I am willing to get up and open and close the same door 5 times in a 2 minute period!

    • eric
      Posted June 3, 2015 at 11:07 am | Permalink

      Ours meows but you can hear the ‘burr’ in her meow from an underlying purr going on. Sort of a “Mmmmmrra” rather than the typical “mraaaooow”

      • Mark Sturtevant
        Posted June 3, 2015 at 4:08 pm | Permalink

        With talkative cats like those I always meow back, and with some cats we have quite a conversation. Our neighbor cat down the street is non-stop talkative.
        The problem is, then, that when I get into these conversations with a cat I feel it would be rude to stop so I just keep meowing, wishing for someone to bail me out.

      • winewithcats
        Posted June 3, 2015 at 7:35 pm | Permalink

        Mine does that as well. It sounds like the video cat, except it’s just a brief comment instead of an entire monologue. That must mean that I’m a skilled executive assistant?

  6. docbill1351
    Posted June 3, 2015 at 11:17 am | Permalink

    Kink has several distinct vocalizations. He also responds to certain phrases.

    If he comes up to me and gives a questioning non-purr meow: mrrr-YOW? Followed by a chewing motion with his mouth, it means he’s hungry.

    If I ask “Are you hungry?” No response.
    If I ask “Do you want a bird?” No response?
    If I ask “Do you want some CAT FOOD?” He makes a mrrrrrrPP sound and runs to the kitchen.

    When Kink comes into a room he always announces himself, usually with a meeeowwPP! But when he’s in a really good mood he has a three tone that starts high, goes low then high at the end: mmrrrrr-oooo-YOWWWW! Sometimes with an imbedded purr.

    Hey, stop laughing, this is science!

  7. Posted June 3, 2015 at 11:31 am | Permalink

    My guess is that this vocal element is cat-specific

    As a long time representative of the dark side (dog owner) there is a difference between an excited/happy bark and an alarmed/aggressive bark. But given the article and the subsequent comments, it seems cats are making much more subtle and complex vocalizations than dogs.
    The lizards don’t generally make a lot of noise.

    • eric
      Posted June 3, 2015 at 1:37 pm | Permalink

      I’ve owned both; the wide range of signals is there (in cats), but yes I agree with you, with cats its more individual-specific and so harder to figure out ‘on the fly.’ I can walk up to a new d*g and have a good idea of their mood. Its not so easy with cats, you have to know the individual animal better. This should not be too surprising, as (IIRC) the time of cat domestication is shorter and the domestication process for each was different. I don’t think we selectively chose cats that were easy to communicate with/give orders to; we selectively chose cats that were great at killing the mice in the granary.

      • Posted June 3, 2015 at 1:59 pm | Permalink

        I thought about that as well. I suppose it is likely that different traits would have been favored in a cat when humans first began to domesticate them.

  8. Posted June 3, 2015 at 11:49 am | Permalink

    Purr spectra…clearly I studied the wrong organism.

  9. E.A. Blair
    Posted June 3, 2015 at 12:11 pm | Permalink

    I can definitely tell the difference among my older cat’s purrs. She has her ordinary purr, her solicitation purr, and something I call her Nirvana purr, which has a loud, sustained musical tone that she uses when she appears to be especially content, as when she’s curled up against me at night. She vocalizes every time I pet her as well.

    Paul Layhausen, ethologist and author of Cat Behavior: The Predatory and Social Behavior of Domestic and Wild Cats (a book I have mentioned many times) noted the many different circumstances under which a cat purrs: when at rest, in pain, in distress, and gave what I think is a very good interpretation of what the purr’s message is: “I am not a threat.” with the subtext, “Please be nice to me.”

    Leyhausen’s book is available on Amazon, but the cheapest used copy is about $80.00, which, adjusted for inflation, is what I paid for it new back in 1979 ($24.95).

  10. noncarborundum
    Posted June 3, 2015 at 12:24 pm | Permalink

    I do wonder how common that solicitation purr actually is. We’ve had about 10 cats over the years and I don’t think I can recall any of them purring that way. Certainly none of the current 3 seem to.

    Or maybe I’m just tone-deaf to catspeak and my cats are really frustrated with me.

    • charitablemafioso
      Posted June 3, 2015 at 7:39 pm | Permalink

      One of my cats does what sounds like solicitation purring. But it’s never for food (she’ll whine loudly and sink her claws in my leg for food). She makes a sound pretty similar to the solicitation purr when she’s stretched out on me, kneading my chest. For her, it’s a purr of ultimate contentment.

    • Diane G.
      Posted June 4, 2015 at 4:35 am | Permalink

      I’ve had a lot of cats in my life and don’t remember any solicitation purrs.

  11. Kevin
    Posted June 3, 2015 at 12:42 pm | Permalink

    I have definitely noticed in both of our cats two distinct purrs.

    One is normal, happy, I am being pet and I am warm, etc., etc. The other is I just had a bath or something very stressful like a car nearly ran me over and I am in utter mental pain. The second kind of purr is unexpected; they are clearly not happy but maybe they are comforted by their owner. Ha, like that ever happens.

  12. Posted June 3, 2015 at 1:12 pm | Permalink

    I’m owned by cat(s), over a lifetime, but recall that the most annoying call I’ve ever heard in nature is that of baby bears. There’s no mystery for me in why such calls evolved–unignorable! What’s interesting here is that one of our domesticated spp/companions may have acquired the “annoying” part through long cohabitation. Heh.

  13. Gregory Kusnick
    Posted June 3, 2015 at 1:21 pm | Permalink

    If the “meow” element in the purr has indeed evolved, it would be through a combination of natural and artificial selection: those cats with more disturbing purrs got more food from humans and hence left more offspring.

    Seems to me that artificial selection requires more than just human involvement in the selection process. There must be some element of human purpose or conscious intent in the selection criterion. I don’t see how that applies in this case; it’s not like humans deliberately planned to breed cats with distinctive solicitation purrs.

    So I’d be inclined to classify this as a case of pure natural selection adapting the animal to an environment that includes humans.

  14. Jeff Rankin
    Posted June 3, 2015 at 1:36 pm | Permalink

    and that the frequency of vibration acts to heal things like broken bones (I can’t vouch for that and can’t be arsed to look it up, but I know there was a paper.)

    I’ve heard this too. When I broke a collarbone a few years ago I was told a vibrating massager thingamajig would help the healing process.

    • E.A. Blair
      Posted June 3, 2015 at 2:07 pm | Permalink

      Back in 2001 I had a severe break in my left humerus about 4 cm just above the elbow. Because of the leverage on the bone so close to the joint and the fact that it was a complex fracture (the bone shattered – not a clean break), I ended up having a number of surgeries. Part of my treatment was an ultrasonic device that I was supposed to strap onto my arm and use for several hours each day. It occurred to me while I was using this device that it felt a lot like when I held one of my purring cats. I did, in fact, find the treatment rather soothing. In a successive surgery, I found out that they had miniaturized the process and they put an implant in my arm that was supposed to do the same thing. I couldn’t feel its effects, and even though its battery has long gone dead it’s still stuck in my arm and causing me problems whenever I go through a metal detector. I think I might have done better treating my arm with the application of a purring cat.

      • Mark Sturtevant
        Posted June 3, 2015 at 4:12 pm | Permalink

        Maybe the idea was that the sound would generate heat, and the resulting increased circulation would speed up healing.

      • Diane G.
        Posted June 4, 2015 at 4:37 am | Permalink

        That is so interesting!

  15. E.A. Blair
    Posted June 3, 2015 at 2:26 pm | Permalink

    Cats differ widely and a lot of this depends on their experiences. Most of my cats have been shelter cats (two were strays) and there was one who was a shelter cat who had been a street cat. The (hypocritically named, since they aren’t a no-kill shelter) Anti-Cruelty Society of Chicago had a cat that looked so much like the cat I already had that they could have been twins – except for size. Freti* was almost feral, and it was a year before he even let me touch him. Once the barrier was breached, he became a sweet and loving cat, although he never liked being picked up or held – it drove him into a panic. His purring was the first time I heard the “singing” or “musical” purr (see my previous post). It was this that clued me in to the nuances of the purr. Freti’s purr reflected his mood, and when he used the singing purr, he seemed to be at his most content.

    *Freti’s name came about because his shelter diet made his poop really reek. It took two weeks to get him on a cat food that didn’t stink up the apartment. “Freti” is an Old Norse nickname that means “Little Foul-Farted One”.

  16. Posted June 3, 2015 at 2:31 pm | Permalink

    Mrrrp

  17. Posted June 3, 2015 at 3:04 pm | Permalink

    “(I can’t vouch for that and can’t be arsed to look it up, but I know there was a paper.)”

    You’re not being deliberately lazy to give yourself and excuse for using that phrase, are you Jerry? 😀

    /@

  18. Sebastian Dieguez
    Posted June 3, 2015 at 3:12 pm | Permalink

    I love this paper! It’s not new though, was published in 2009.

  19. Les
    Posted June 3, 2015 at 4:35 pm | Permalink

    Prof CC doesn’t own a cat? That’s a surprise.
    Will you get on upon retirement?

    • Posted June 3, 2015 at 10:11 pm | Permalink

      No; he’s been bereft of feline overlordship for a while.

      Rumor has it that this insufferable deficit will be remedied this summer when he is to be bound to a Bengal.

      b&

  20. Sheila B and Zin
    Posted June 3, 2015 at 4:50 pm | Permalink

    Zinnia’s solicitation usually involves knocking things off the window sill in our bedroom, usually around 5 am. She does a chirrupy purr when she eats though.

    • Diane G.
      Posted June 4, 2015 at 4:41 am | Permalink

      Winston’s solicitation behavior progresses from Slightly Annoying Behavior to jumping to the top of the bookcase and threatening to jump down into the potted palm. The palm is now a ghastly sight.

  21. Posted June 4, 2015 at 1:32 am | Permalink

    We had to lose our old tabby moggie at Hogmanay due to very old age and increasing ill-health. She was a very loving little cat and had one of the loudest purrs I remember amongst the many cats who’ve shared my life. There was an obvious difference between her solicitation and contentment purrs and I’ve been aware of this semi-vocalisation purr for some time.
    Our current cat is a re-homed silver tabby bengal female who’s eight years old. Although she does purr, it’s very quiet and can only be heard when you’re very close to her. She doesn’t seem to have a solicitation purr, but is otherwise very vocal and it’s possible to hold miaowing conversations with her.

  22. Posted June 4, 2015 at 2:32 am | Permalink

    My cat doesn’t normally use a solicitation purr. He has other methods of getting my attention. If I’m on the computer, he starts by hitting my arm. (He’s also been known to go for the face.) He then looks at me in the eyes and meows repeatedly. If it’s food he wants, he knows where I keep it. He sits there and meows over and over.

    Also, I find it odd that the recommended videos ,after the one posted on the blog, contained one Hitchens video and some “thug life” cat videos.

  23. Rachel
    Posted June 4, 2015 at 8:26 am | Permalink

    My cat, Sophie, doesn’t purr for food, but she does purr for cuddles, and I’ve noticed that there’s a difference between the way she purrs when she wants something and the way she purrs when she has what she wants. She also incorporates this small, dry, very needy-sounding meow. I realize I’m being played, but I love her, so I don’t care. 🙂

    It’s interesting – to me, anyway – observing the difference between Sophie and my other cat, Lloyd. I’ve had Sophie since she was two months old; she’d been a feral, and she’d only been at the shelter for a couple of days, so I was really the first human being to have much interaction with her. Anyway, I find her vocalizations much more varied and … personal … than I do Lloyd’s, whom I adopted when he was three years old, and who’d had previous owners.

  24. Diana MacPherson
    Posted June 5, 2015 at 6:48 am | Permalink

    When I was patting my friend’s cat, he meowed in a way that clearly told me, “don’t pat my face, pat my back!” The cat might as well have said it in English, his demands were so clear to me.

    And I sneezed later as I’m allergic to cats but who can resist patting a kitteh?

  25. Posted June 6, 2015 at 7:04 am | Permalink

    Every time this work gets brought up, I go listen to the purrs again, and I never find one more “urgent” (or “less pleasant”) than the other. They are obviously distinct, but I just can’t seem to work up different emotional responses to them.

    I guess this confirms what my cat has long suspected: that I am pretty much the worst monkey ever.

    • Diane G.
      Posted June 6, 2015 at 11:04 pm | Permalink

      That’s funny! 😀


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