February 6: The Baby Purr

A few years ago my husband and I watched a Cat Documentary on Netflix. While I can't remember what it was called, we both specifically remember one part that we quote all the time. We learned that cats have different kinds of purrs, one of which is the same frequency as the cry of a human baby, so humans respond to it more quickly than other purrs. We started calling this "the baby purr". In lieu of finding the actual documentary, I did find the study that discovered the baby purr, titled "The cry embedded within the purr" by Karen McComb, published in Current Biology, August 2009 whose abstract summaries that "We discuss how the structure of solicitation purrs may be exploiting an inherent mammalian sensitivity to acoustic cues relevant in the context of nurturing offspring." The first few lines of this BBC story say it all in a more palatable way:

Researchers at the University of Sussex have discovered that cats use a "soliciting purr" to overpower their owners and garner attention and food.

Unlike regular purring, this sound incorporates a "cry", with a similar frequency to a human baby's.

The team said cats have "tapped into" a human bias - producing a sound that humans find very difficult to ignore.

It turns out that adult cats who live in the wild rarely purr at all; only kittens purr to their mothers in the wild. But domesticated cats not only retained the trait to purr, they learned to purr even as adults, in order to communicate to their human owners. Domesticated cats created a specific language that they use exclusively with us including a variety of purrs. Dr McComb said cats learn to dramatically exaggerate the solicitation purr when it proves effective in generating a response from humans. When the research team played the recordings of purrs back to human volunteers, even those people with no experience of cats found the soliciting purrs more urgent and less pleasant than other purrs. Fascinating!

One of our three cats (Fela) does the baby purr sound all the time. It is a noticeably different sound and frequency than his other purrs. He is already very vocal, with a huge variety of sounds he uses to communicate with us, but the baby purr is definitely one of my favorites. He tends to use it when he wants attention, basically saying to us "Please pet me, please love me, please cuddle with me, please hold me, please pay attention to me." And you cannot help but to give him what we wants. He has definitely tapped into the evolutionary advantage of crying like a human baby, knowing we HAVE to respond. 

I delight in this purr as much as I delight in the knowledge of the purr. I love witnessing science and evolution sitting right here in my lap. 

With delight,

♥Jamie