Why do cats knead?
Kneading is that rhythmic movement you might have seen when your cat pushes her paws, usually against something soft like a blanket or your lap. It's called 'kneading' because if you could persuade the cat to do the same thing to a lump of dough you would end up with a decent loaf of bread. So when and why do cats do this?
Picture from: FASTILY
As to the 'when' cats often knead when they are lying on their side while being petted. Cats will often purr while kneading which definitely suggests that the kneading is something done when the cat is happy and content. But why do they do it?
Kneading probably has its roots in kittenhood. When feeding, young often knead mama's tummy probably as a way to stimulate milk flow, though kneading might also comfort the kitten with the assurance that mum is right there. It may even be a way to spread kitten’s own scent onto a nursing nipple. Cats are born blind and deaf so in early days the world is a very scary place. But one thing which is well developed from birth is a kitten’s sense of smell.
A study carried out by scientist Robyn Hudson and his colleagues showed that within 12 hours of birth kittens already have a preference for posterior nipples and by day 3 each kitten has a preference for a particular nipple. Indeed 86% of kittens went to use the same nipple even after the mother changed the side she lay on to nurse. Earlier it was suggested that kittens were competing for the nipple which gave the most milk, but Hudson disagreed. His research showed that there was no correlation between kittens’ use of a particular nipple and their weight gain, and also no correlation with their milk intake (ref). It may be possible that by kneading around the nipple, the kitten spreads her own scent so when the next meal comes along she will more easily recognise where the feeding bar is.
Of course a well-fed kitten is a happy kitten and this kneading behaviour may well reinforce the feeling of content. So most cats carry it to adulthood. When a cat feels particularly happy it will start kneading a soft blanket or your lap whichever happens to be on hand (or paw). Of course by doing so the cat also leaves her scent on the kneaded surface thus claiming your lap or that blanket as her own. Cats which have grown up together or have a good relationship will also knead each other.
The fact that most cats will knead if happy and relaxed has led to the abandonment of the earlier theory that kneading is a sign of anxiety from cats that were prematurely separated from their mothers. However there are a couple of other suggestions which have been put forward. One interesting idea is that cats will knead to create a comfortable place to sleep. A wild cat, for example, will knead grass into a soft bed,rather as a dog may turn in circles before lying down.
Another theory proposes that cats knead to stretch their legs and paws. Most cats will knead just with front paws but some cats will use all four. Many cats will also extend their claws when kneading which can get somewhat uncomfortable when they do it on your lap. Most humans find this behaviour adorable but you may want to wear thick denims or put a blanket between your lap and a kneading cat.
Robyn Hudson, Gina Raihani, Daniel González, Amando Bautista and Hans Distel. Nipple preference and contests in suckling kittens of the domestic cat are unrelated to presumed nipple quality. Dev Psychobiol (2009) vol 51(4) pp:322-32. https://onlinelibrary.wiley.com/doi/abs/10.1002/dev.20371