The Secret Life of 'Um'

When one person asks another a question, it takes an average of 200 milliseconds for them to respond. This is so fast that we can’t even hear the pause. In fact, it’s faster than our brains actually work. It takes the brain about half a second to retrieve the words to say something, which means that in conversation, one person is gearing up to speak before the other is even finished. By listening to the tone, grammar, and content of another’s speech, we can predict when they’ll be done.

This precise clockwork dance that happens when people speak to each other is what N.J. Enfield, a professor of linguistics at the University of Sydney, calls the “conversation machine.” In his book How We Talk, he examines how conversational minutiae—filler words like “um” and “mm-hmm,” and pauses that are longer than 200 milliseconds—grease the wheels of this machine. In fact, he argues, these little “traffic signals” to some degree define human communication. What all human languages have in common, and what sets our communication apart from animals, is our ability to use language to coordinate how we use language.

I hopped into the conversation machine with Enfield for a very meta chat about the big impacts of tiny words and pauses on human interaction. An edited and condensed transcript of our interview is below.

: Can you explain what the