Nearly every language and every culture has what are called “filled pauses,” a notoriously difficult-to-define concept that generally refers to sounds or words that a speaker uses when, well, not exactly speaking. In American English, the most common are “uh” and “um.” Until about 20 years ago, few linguists paid filled pauses much attention. They were seen as not very interesting, a mere expulsion of sound to take up space while the speaker figures out what to say next. (In Russian, filled pauses are called “parasite sounds,” which is kind of rude.) But since then, interest in filled pauses has exploded. There are conferences about them. Researchers around the globe, in dozens of different languages, dedicate themselves to studying them. And yet they still remain poorly understood, especially as new forms of discourse begin popping up. Read more.