From an early age many of us are taught that when cats purr, they’re telling you they’re happy. While purring is thought to be partly voluntary and partly instinctive, research suggests that cats can purr for various reasons, using the soft rumble as a way of communicating and as a form of self-soothing or even healing. This is why cats will often purr when they’re injured, or after a stressful event.
Kittens are born blind and deaf, remaining so until they are around two weeks old. However, they begin purring after just a few days, primarily to let their mothers know where they are, and to attract their attention at feeding time. This behaviour continues into adulthood and will be familiar to cat owners who are treated to a coercive display of purring come dinner time. But this is just one of several different ways in which the purr is used.
Cats often purr when humans stroke them, leading to an association between purring and pleasure. Observed feline behaviour suggests they may also be trying to encourage further interaction, as if to say “please continue to stroke me”.
A 2009 study found that cats can conceal a cry within their purr that triggers a nurturing instinct in their owners, similar to the cries of a human baby. The study observed that when purring to solicit food, the noise cats made was “more urgent and less pleasant”, suggesting they can manipulate their purrs to communicate different things.
According to New Scientist readers, cats will also adapt noises like their meow to elicit a response from their owners. This means that if a cat were to have a deaf owner, it is likely they would meow less once they learned it did not trigger a response. However, the same cat would probably continue to purr, without changing the frequency of the sound.
Research into feline behaviour has lagged behind that of dogs, but a 1991 study concluded that purring emanates from the cat’s voice box, or larynx. When cats breathe, they dilate and constrict the glottis, the area around their vocal cords, in a rapid, rhythmic fashion. As the air vibrates over the laryngeal muscles of their larynx, the purring sound occurs.
But why do they purr after a stressful event? A 2001 study published in The Journal of the Acoustical Society of America showed that domestic cats and some species of big cats, including pumas and cheetahs, could purr at frequencies optimal for pain relief and even bone repair.
So how can you tell why your cat is purring? Your best chance of understanding them is to look at their body language and the context. If they’re purring first thing in the morning, they may be asking to be fed. If you’ve just returned from a day at work, they might be saying hello and if they are sitting on your lap, purring contentedly, they might just be signalling their approval.