According to the Guardian:
For those with a deep suspicion of cats and their motivations, this may well be the scientific proof they have been waiting for. New research has finally laid bare the degree to which cats exploit humans.
Instead of loud miaowing when they want food, behaviour likely to have them ejected from the bedroom, some cats disguise their cries for attention within an otherwise pleasant purr. The result, according to a study published tonight in the journal Current Biology, is a complex "solicitation" purr with a high-frequency element that triggers a sense of urgency in the human brain. Owners find it irritating, but not irritating enough to kick the cat out, and feel driven to respond.
. . .
However, not all cats have the cry; the researchers, who examined 10 cats, found it only in those living in single-person households. "We found that cats learn to dramatically emphasise the peak when dealing with human owners that have a one-on-one relationship," McComb said.
There's more at the link.
Miss D. and I have each been 'owned' by several cats during our lives so far, and we're currently regarded by Gremlin, Oleg's 'owner', as surrogate humans (we feed him, play with him and clean his litter-box when Oleg's out of town). These photographs of Gremlin were taken by Oleg - as if I needed to tell you that!
We're also friends with a neighborhood cat who keeps trying to persuade us that we really, really need a house-cat of our own, and he'd loooove to apply for the vacancy. I think we'll have to test this theory on them, and see what emerges.