Phatic speech was first noticed seriously in 1923 by the academic Branislaw Malinowski. He noted that people spend a lot of time saying effectively meaningless things (Hello! Whoops! How are you? Toodle-pip!) and his theory was that people did it in an attempt to keep everyone friendly.
Douglas Adams' character Ford Prefect in The Hitchhikers' Guide To The Galaxy Trilogy came up with a parallel theory:
...it is worth repeating...the theories that Ford came up with, on his first encounter with human beings, to account for their peculiar habit of continually stating and restating the very very obvious, as in 'It's a nice day,' or 'You're very tall,' or 'So this is it, we're going to die.'
His first theory was that if human beings didn't keep exercising their lips, their mouths probably shrivelled up.
After a few months of observation he had come up with a second theory, which was this - 'If human beings don't keep exercising their lips, their brains start working.'
But which of these theories is the more likely to be true?
Well, of the three authorities quoted, Ford Prefect was definitely not a genius; Douglas Adams definitely was a genius; and Bronislaw Malinowski I don't know much about, but he gained PhDs in philosophy and science in two different languages, so he was presumably no slouch.
But the foremost authority on this subject is, of course, you, yourself.
Why do you keep saying completely meaningless things? Things that don't convey much at all, and definitely don't expect an answer? Things like hey?
What would you think of someone who didn't?
Phrase To Use Today: a phatic one (Hello will do). The word phatic comes from the Greek phatos, which means spoken.