The Null Device
Researchers at the University of Sussex have discovered how domestic cats have developed a purr that psychologically manipulates humans, subtly triggering a sense of urgency without being as confronting as a meow. The "soliciting purr" contains an embedded high-frequency component similar to a cry:
Dr McComb and her team set up an experiment which tested human responses to the different purring types. She says: “When humans were played purrs recorded while cats were actively seeking food at equal volume to purrs recorded in non-solicitation contexts, even those with no experience of cats judged the ‘solicitation’ purrs to be more urgent and less pleasant.”
Not all cats, however, use this solicitation purring: “It seems to most often develop in cats that have a one-on-one with their owners rather than in large households where there is a lot going on and such purring might get overlooked. Meowing seems to be more common in these situations.”Cats tend to use the "soliciting purr" at times such as early in the morning, to elicit compliance from humans who may otherwise prefer to do something else, such as remaining asleep. It appears to be individually learned rather than an evolved instinct. There are more details, including embedded video, here.