From Live Science
"If you've ever wondered who's in control, you or your cat, a new study points to the obvious. It's your cat.
Household cats exercise this control with a certain type of urgent-sounding, high-pitched meow, according to the findings.
This meow is actually a purr mixed with a high-pitched cry. While people usually think of cat purring as a sign of happiness, some cats make this purr-cry sound when they want to be fed. The study showed that humans find these mixed calls annoying and difficult to ignore.
"The embedding of a cry within a call that we normally associate with contentment is quite a subtle means of eliciting a response," said Karen McComb of the University of Sussex. "Solicitation purring is probably more acceptable to humans than overt meowing, which is likely to get cats ejected from the bedroom.""
That's my cat's description. He can be such a pain that you simply cannot ignore it. He purrs and meows simultaneously, not to mention he will literally sit on my head when he needs more food or to go out.