A recent study has shown that people subconsciously can tell the difference between a pleading or soliciting meow and a run of the mill, casual one just by listening to sound clips taken from different felines in different situations. The subjects said the soliciting sounds came across as more urgent and less pleasant than a normal meow, much like the cries a human baby makes when she's hungry.
In fact, further studies have proven that a cat's cry for food or attention shares a remarkable similarity in frequency to a baby's cry. It's not coincidence- it's pure, kitty evil genius.
Using their expertise in Soviet-style subliminal advertising, cats adjust their purrs and meows to include this frequency which then prompts their owners into responding to them more quickly. Like well trained animals ourselves, we respond because, not only is the sound annoying to us, but it also stimulates our natural instinct to immediately nurture anything that sounds like our offspring, even if it is covered in fur and named Mr. Bojangles.