“It does seem to be the case that ‘um’ generally signals a longer or more important pause than ‘uh’,” says Mark Liberman, a linguist at the University of Pennsylvania.
At least that’s what he thought.
Liberman has been studying these so-called “filled pauses” for almost a decade, and he has made a rather curious discovery.
“As Americans get older, they use ‘uh’ more,” he says. “And at every age, men use ‘uh’ more than women.”
If you look at “um”, exactly the opposite is true. Younger people say “um” more often than older people. And no matter the age, women say “um” more than men. Nobody, not even the linguists, were expecting this result; until they studied these hesitations, they thought it was more about the amount of time a speaker hesitates than who that speaker is.