Whenever we stroke a cat, they sometimes respond with a soft purr, and so we think the reason why cats purr is because they feel happy or relaxed, or something of the sort. Many researchers thought that cats' purring was caused by voluntary muscle contractions of the larynx, but new studies have shown that it is much closer to snoring than a voluntary response when they feel comfortable or stressed.
Although the researchers do not rule out the possibility that cats purr because of voluntary muscle contractions, they argue that it wasn't the sole cause for the purring. Instead, their research suggests that it was the flow of air that activated the vibrations causing the purring, much like how we snore when our breathing is obstructed. Despite not having fully understood the reasons behind purring, scientists are in consensus about some aspects of purring such as it is used as a signal by kittens so their mothers can locate them, it produces serotonin in cats, it helps in healing wounds, and purring is not merely a response to positive stimulus, but it is also done when cats are stressed.
To learn more about the biomechanics of cats' purring, check out the article on Wired.
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