While dogs can often be taught new tricks, cat-owners will be all too aware that it can be very difficult to persuade them to do something they don't want to do. Eddie Izzard summed it up best in his legendary Pavlov's cat sketch, where felines are quite capable of outfoxing (outcatting?) eminent Welsh-Russian psychologists. Real cats may be less devious, but only just - new research suggests that they are very skilled at getting their human owners to do their bidding.
When they want food, domestic cats will often purr in a strangely plaintive way that their owners find difficult to ignore. By analysing the structure of these calls, Karen McComb from the University of Sussex has found out why. On the surface, the "solicitation purrs" are based on the same low-pitched sounds that contented moggies make, but embedded within them is a high-pitched signal that sounds like a cry or a meow. It's this hidden signal that makes the purr of a hungry cat so irresistible to humans.
McComb has a long history of research into animal communication and she has studied the calls of African elephants, red deer, lions and macaques. But it was her own cat, Pepo (pictured above), who provided the inspiration for this study.
"He consistently woke me up in the mornings with very insistent purring," she said. "I wondered why this purring sounded so annoying and was so difficult to ignore. Talking with other cat owners, I found that some of them also had cats who showed strikingly similar behaviour. As I was an academic who actually worked on vocal communication [in mammals], I had the right background, tools and collaborators to tackle this question directly."
McComb recorded 10 different cats purring under various circumstances, equalised the volume of all the recordings, and played them to 50 people. Her volunteers rated the purrs of a food-seeking cat to be more urgent and less pleasant than purrs made while resting, sitting or petting. When given a choice between the two purr categories, listeners consistently rated the 'solicitation' purrs as being more urgent. They could do so even if they had never owned a cat before (although cat-owners were a little more accurate).
When McComb analysed the acoustic structures of the different purrs, she found that the solicitation purrs have an unusual high-frequency peak that doesn't fit with the rest of the call. At a frequency of around 380 Hz (middle G or thereabouts), this extra sound stood out from the typical low frequencies of a purr, and is more like a cry or a meow. The frequency is actually very similar to that of a crying infant, so small wonder that it tugs on the human heartstrings.
Normal purrs are made by rapidly vibrating the muscles of its vocal cords, but a cat needs to deliberately push air past these muscles - a phenomenon called 'voicing' - to produce the higher-pitched component. This voiced acoustic feature is critical for a cat's food-acquiring antics, for McComb showed that the more intense it is, the more urgent and unpleasant the resulting purr to humans
As the ultimate test of its importance, McComb took recordings of solicitation purrs and removed the voiced element, leaving everything else the same. Without it, human volunteers could no longer tell the difference between these purrs and others.
McComb suggests that cats (and even cheetahs) have this small voiced component in their normal purrs anyway. She says, "We'd be interested to see if kittens use it when their mothers are trying to wean them or don't want to feed them any more."
It certainly seems that cats who spend a lot of time around humans have learned that exaggerating the voiced peak is a good way of manipulating their owners' sensory sensitivities. The resulting calls are also less harmonic, which makes it more difficult for people to become accustomed to them. Plus, they're probably quite useful for conceal drilling activities (see 1:24 in the video).
The manipulative purrs seem to be most frequently used by cats who have the most one-to-one contact with their owners, rather than those who live in large households where purring might get drowned out by the general din. In fact, the private nature of these noises made the simple act of recording cat purrs surprisingly difficult.
"I've worked on communication and cognitive abilities in a wide range of mammals including African elephants and lions - but cats were one of the most challenging subjects to date," she said. Cats often purr in private with their owners and they tend to clam up or leave when strangers turn up. McComb could record Pepo's purrs, but she actually had to train cat-owners to use the recording equipment themselves. These obstacles are reflected in the paper's brilliant Acknowledgments section, which reads:
"We are indebted to Archie, Clyde, Fuzzy, Hippolythe, Marbles, Max, Mojo, Morgan, McKee, Pepo, Socks and their long-suffering owners for participating,"
Reference: Current Biology; citation unavailable at point of writing.
Image: Pepo the cat by Karen McComb
More on animal communication:
- Scientists tickle apes to reveal evolutionary origins of human laughter
- Eland antelopes click their knees to prove their dominance
- Singing fish reveal shared origins of vertebrate vocals
- Crocodiles signal hatching time by calling from inside their eggs
- Chimps call during sex to confuse fathers, recruit defenders and avoid competitors
Life Science
Comments
This explains why one of my overlords is so incredibly good at waking me up too early to feed him and give him cuddles. He gives me that cry and taps my eyelids!
Posted by: Brigit | July 13, 2009 12:27 PM
This is silly. Everyone knows cats communicate that they're hungry by biting you really hard on the ankle!
Posted by: Harlan | July 13, 2009 1:46 PM
They are criminal masterminds.
Posted by: Daneel | July 13, 2009 2:36 PM
My cat used to get shut out of my bedroom when he woke me up at night. He expressed his loneliness by standing outside the door and howling like a beagle: wowwwww, wowwwww, up and down the register. I wish I had a recording of that!
Posted by: Lilian Nattel | July 13, 2009 3:27 PM
Pepo's pet dosen't know how lucky she is. My former owner used to stand on my chest, put her face right down next to mine and SCREAM! Ah...the kitty version of morning breath, coupled with 150-decible yowling...what a pleasant way to wake up in the morning!
Posted by: Kate | July 13, 2009 4:05 PM
Mine just headbutt, scream and bite....
Posted by: RobC | July 13, 2009 6:01 PM
My cat walked across my keyboard and clicked the link to one of the ads while I was trying to read this. I wonder if she's got something to hide...?
Posted by: Kim Hannula | July 13, 2009 6:17 PM
This is not the only combination purr+noise. Our Cassini, a very vocal cat with a large vocabulary, has several variants of what I call a "churr", which is a very pleasant sound, made typically when he wants some petting. I use it to call him in when his outside time expires (we have eagles, owls, racoons, and now coyotes in the neighborhood, so we need to keep an eye out, but he is our athlete/hunter and really pines if he cannot check his perimeters at least once a day). The food call comes later and is quite different. I have also noticed that all our cats switch to a lower pitched yowl when carrying prey (real or fake). At least we can tell when they are bringing in a present before we see them.
As for manipulating their staff. Well, duh! The cat words may differ from cat/human combo to other cat/human combo, but they certainly figure out a way to tell us what they want, and we seem to be hardwired to be unable to refuse them.
Posted by: Gray Gaffer | July 13, 2009 6:49 PM
Well I wish my cat would learn that purr. All he does is meow all day and all night, every second that he isn't getting attention from me.
Posted by: Katherine | July 13, 2009 8:34 PM
Finally, someone has picked up on this. We had a cat that never learnt to purr his whole life, but CCS (who is 10 now) has a large
vocabulary and about 2 years ago, we discovered she was adding this extra sound to her purring. Her purring was already quite loud
but there was this extra "trill" sound, so that it was modulated by the purring. So imagine a loud, purring cat, that adds a high pitched whine to here little song, so it trills with the purr - so we had 2 or three levels of sound. She does this when we are on the bed,
not necessarily looking for food, but perhaps comfort. This song is really quite noticable. Cleo fits the profile because she is an only cat in a quiet household with lots of 1 on 1 time with her humans. The other "human modifying behaviour" trait is what we call "the bedroom dance" - there has to be 3 on the bed. Two is not good enough. If 2 are on the bed, she will seek the 3rd person out and repeatedly brush against them and sit/jump on laps until the second person is also on the bed. We know it is a communication because the cat will loop towards the bedroom and where the person is repeatedly until they go to bed and within seconds the cat will materialise, purring and singing her little song. So there is a lot to cat behaviour and they are extremely complex social manipulators.
Posted by: rachel | July 13, 2009 10:59 PM
How totally fascinating. I expect to get a cat in six weeks or so (after not having one for more than 30 years, because of an allergic husband) and look forward to reacquainting myself with their ways.
The cat-less years were filled with ferrets, because they don't aggravate allergies, but they are generally silent.
I especially recall Katie, who lived with me in SW15. I could tell from all around the house when Katie came in with a bird or a mouse. The continuing growl was like no other sound.
We know that human mothers can tell whether their babies are hungry. But can a human mother hear when someone else's baby is hungry? I suspect there may be a common, hidden note shared by all hungry babies too.
Posted by: Diggitt | July 13, 2009 11:13 PM
Abstract which has DOI
Posted by: rdb | July 14, 2009 1:01 AM
I hear that sound often with twin old men cats who like to go out and mouse at two in the morning. Aaarghh... and they tagteam if they are both in the mood. Relentlessly. If there is a door between them and a person, they scratch at it and make that noise until they are let out. They have different greeting sounds, but MAN do their I WANT OUT sounds sound alike.
Posted by: gmm | July 14, 2009 1:33 AM
Our "Noodle" sits on the hope chest at the foot of the bed and waits for the first sign of movement. As soon as one of us yawns, sighs or stretches, the high pitch purr starts until my husband gets up and feeds them. "Butthead" just meows.
Posted by: Mich | July 14, 2009 12:02 PM
My understanding is that a purr by itself isn't really meaningful -- it's basically "heavy breathing". People just think it means pleasure because they can hear it best when they're petting or holding the cat.
That said, darn right cats are manipulative! Mine has gotten quite adept at telling me when she wants water, food, or to go outside. (And that last was only an option for the last couple of years, by which time Gremlin was already some 12-13 years old.) Also, she uses posture and gaze rather (sometimes in addition to) sound, because I'm hard of hearing.
The nasty part is they learn from "what you do, not what you say" -- remember that bit about erratic reinforcement being most effective? Feed a cat scraps from the table once, and they'll be hovering by you at every mealtime for the rest of their lives!
The flipside of that was that, once she did get to go outside (with me keeping an eye on her), she rapidly learned that if she wanders out of bounds, I'll pick her up if needed to get her back onto my own front yard. (She's too old and fat to dodge me.) Which doesn't actually stop her wandering into the neighbor's yard if I'm not actually out there with her, but if I go out there and glare at her, she'll scoot back over the borders I taught her.
Posted by: David Harmon | July 15, 2009 11:30 PM
As the keeper of several different cats over the past 45 years I have learned they each have unique ways of communicating. The meow/purr combo is very common.
Though my favorite was the big fluffy gray tabby I had in high school who would wake me up by walking on the bookshelf and knocking things off. He broke a few bits of china (including a cat figurine). He resorted to that after failing to wake me from my teenage slumber (which if I can go by my own teenage children is something close to a coma) by sitting on my chest, purring very loud, kneeding and drooling.
Posted by: Chris | July 16, 2009 1:39 PM
You might find this blog "Please can I have some more?" http://cabiblog.typepad.com/hand_picked/2009/07/please-can-i-have-some-more.html of interest. It's based on a study published in CAB Reviews, which suggests pets may be able to negotiate with their owners over what, when and how much they are fed. It seems that there are similarities with the way babies manipulate their caregivers over food to ensure attention.
Posted by: David | July 17, 2009 11:30 AM
You might find this blog "Please can I have some more?" http://cabiblog.typepad.com/hand_picked/2009/07/please-can-i-have-some-more.html of interest. It's based on a study published in CAB Reviews, which suggests pets may be able to negotiate with their owners over what, when and how much they are fed. It seems that there are similarities with the way babies manipulate their caregivers over food to ensure attention.
Posted by: David | July 17, 2009 11:30 AM