Cats purr by rapidly moving the muscles of their larynx (voice box) and diaphragm (the muscle at the base of the chest cavity) at around 20 to 30 times per second. As the cat breathes, air touches the vibrating muscles, producing a purr. The purr is produced during the entire respiratory cycle, unlike other cat vocalizations such as the meow, which are limited to the expiration of the breath.

While many suggest that cats purr from contentment and pleasure, cats also purr when they are injured and in pain. Purring may be linked to the strengthening and repairing of bones, relief of pain, and wound healing. Purring may also be feline self-comforting behavior, first expressed when kittens are only a few days old, perhaps signaling their presence to their mother and encouraging her to feed them. This form of communication continues into their adult lives.

Cats can conceal a cry within their purr that triggers a nurturing instinct in their owners, similar to the cries of a human baby. They can manipulate their purrs to communicate different things, such as when they’re hungry or nervous. Therefore, understanding a cats body language and the context is the best chance of understanding why they are purring.