We think we know what a cat’s purr means.

　　我们以为自己知道猫咪呜呜叫是什么意思。

　　It is arguably the most recognisable sign of animal contentment: a pleasurable rasp that erupts whenever a cat is tickled or petted, the soundtrack to countless sessions sprawled on an owner’s lap.

　　通常认为动物开心时会这样：抚摸或胳肢猫时，猫咪会开心地呜呜叫，躺在主人的大腿上，猫咪会不断发出这样的声音。

　　But that’s not quite the full story. There is a lot more going on with the cat’s purr than you might reasonably expect.

　　如果认为只是这样而已，你就错了。猫咪呜呜叫的背后故事，多到超乎你的想象。

　　Even the ‘how’ was long a subject of debate. Some thought it was linked to blood flowing to the inferior vena cava, a vein that carries deoxygenated blood to the right side of the heart. But with more research it seemed likelier that the noise came from the muscles within the cat’s larynx. As they move, they dilate and constrict the glottis – the part of the larynx that surrounds the vocal chords – and the air vibrates every time the cat breathes in or out. The result? A purr.

　　单是猫咪是如何发出呜呜声这一点，人们都争论了许久。有人认为和血液流到下腔静脉有关，下腔静脉将没有氧气的血液送入右心房时会发出声音。但是更多的研究发现呜呜声更可能来自猫咪喉部的肌肉。当猫儿的肌肉运动时，肌肉就会扩张或压缩声门(喉部声带周围的部分)，因此猫咪每次呼吸时都会震动空气。结果呢?发出呜呜声。

　　Even though science is now fairly sure this is the process, there’s no definitive answer as to what triggers the response. The biggest clue is a neural oscillator deep within the cat’s brain, one that otherwise has no clear purpose.

　　虽然现在科学可以肯定过程就是如此，但是什么引起猫咪呜呜叫，还没有明确的答案。可能与猫咪大脑内一个尚无明确功能的神经振动子有关。

　　But if that neural oscillator is triggered, is it just when a cat is happy?

　　但是触发神经振动子时，猫咪是开心的吗?

　　Sometimes. But only sometimes.

　　有时是开心的。仅仅是有时候。

　　Marjan Debevere is a cat shelter photographer in London who is currently studying for a degree in feline psychology. She is also the owner of four cats – Clive, Hula, Luigi and Archie – who are something of an Instagram sensation (33,000-odd followers and counting, Instagram fans).

　　代贝维尔是伦敦的一名猫咪收容所摄影师，正在读猫心理学。她自己也养了四只猫——克莱夫、胡拉、阿尔奇和路易，她是Instagram上的网红(IG上有33000多粉丝，还在不断增加)。

　　Part of the mystery around the purr is that we often only notice cats purring “when we tickle them in places that they like to be tickled”, says Debevere. Yet they also purr when we’re not around, and the extent of that purring varies between individuals. “All cats are different, some never purr and some will purr constantly,” she says. She draws the comparison between her cat Luigi – a stray who followed someone in to their office and was subsequently taken to a shelter – and Archie, who “moved in from next door” and became part of the family. Luigi purrs little, and Archie a lot.

　　代贝维尔说，问题是我们通常只注意到"胳肢它们喜欢被胳肢的部位时"，猫咪会呜呜叫。但是，我们不在身边时猫咪也会呜呜叫，不同的猫叫声是不同的。她说，"没有两只猫是一样的，有的从不呜呜叫，有的叫个不停。"她比较了她的两只猫，路易和阿尔奇。路易是一只流浪猫，跟着某人来到她们办公室，后来被送到了收容所。阿尔奇"从隔壁搬过来"成了家庭的一员。路易很少呜呜叫，阿尔奇却经常叫。

　　“I’ve photographed more than 3,000 cats so far [at shelters] and no two are the same,” Debevere says. “I’ve witnessed a lot of cats purring when they’re dying, and when they’re being put to sleep. 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.”

　　代贝维尔说："我给3,000多只猫拍过照片(在收容所)，没有两只猫是一样的。我见过许多猫濒死的时候呜呜叫，被安乐死的时候也呜呜叫。兽医说’它们直到生命的最后一刻还在呜呜叫’，人们以为它们呜呜叫的时候是开心的，其实不总是这样。"

　　The study of cats’ behaviour and communication has lagged behind that of dogs, which are usually more willing participants, especially if there is a reward of food involved. But in recent years more light has been shed on the purr.

　　对猫的行为和语言的研究比狗的研究落后。因为狗通常很积极配合，尤其是有食物作奖励的时候。但是近些年来，对猫呜呜叫的研究也有了一些进展。