Item on the Today programme this morning (BBC Radio 4) on the different ways a cat can purr, including what a researcher has named "solicitation purring", which is what many cat staff members get in the morning as a request for food. The researcher thinks that cats have learnt to manipulate their blobs (sorry, their staff) by adding a vocalisation which is, she says, on the same frequency as a baby's cry.
There's a piece on this on the BBC website (for which I've forgotten to add the URL, sorry).
To me, the sound sample sounds more like a highly excited cat ...as the small bit of video shows the cat sitting by a food bowl that's how I would have read the sounds myself. But I'm not a paid researcher, so what do I know?
Our cat has a huge variety of vocalisations and purrs and yes, they're manipulative in the sense that she wants us to do things for her (open doors, food packets, play, tickle etc). They're also hugely endearing, so I suppose I'm totally in thrall to the cat.