Why do we say “um”? What the science says about filler words
19 October 2026 · 5 min read
Everyone says “um”, and almost everyone wishes they said it less. It turns out researchers have studied why for decades, and the answer is more interesting than “nerves”.
Short answer: you’re buying time
Speaking is hard work. While you say one phrase, your brain is already choosing the next words, finding the right one in your vocabulary and lining up the grammar. When that planning runs behind your voice, you have two options: go silent, or fill the gap. “Um” and “uh” are how we fill it.
Fillers are not a quirk of English. French speakers say “euh”, Germans say “äh”, and Japanese speakers say “ano” or “eto”. Almost every language studied has its own sound for the same job.
“Um” and “uh” aren’t the same
In a well-known 2002 paper, the psychologists Herbert Clark and Jean Fox Tree studied thousands of fillers in recorded conversations. They argued that speakers use “uh” to signal a short delay and “um” to signal a longer one. In other words, they work a little like words, and speakers choose between them. Not everyone agrees on every detail, and other researchers have questioned how reliably they predict a pause, but the idea that fillers carry some meaning is now widely discussed.
The harder the choice, the more ums
Fillers track thinking effort, not just nerves. In a classic study, researchers sat in on university lectures across ten subjects and counted the ums. Lecturers in the humanities said far more than lecturers in the natural sciences. Press accounts of the study put it at roughly four to five a minute for humanities lecturers against about one and a half for scientists. The authors’ explanation: the more open-ended the subject, the more choices a speaker has at every point, and choosing takes time.
It fits everyday experience. You say more ums when you’re explaining something you’re still working out than when you’re reciting something you know by heart.
Do listeners actually notice?
They do, and not always in a bad way. A 2007 study recorded brain activity while people listened to sentences. When a speaker said “er” just before an unexpected word, the brain’s surprise response to that word was smaller. The “er” seemed to warn listeners that something less predictable was coming. Those listeners were also slightly more likely to remember the word later.
A 2011 study went further. People who heard a story with “uh” and “um” added remembered more of it than people who heard the same story without. A later replication across English and German partly agreed, though other work finds that too many disfluencies, especially at a fast pace, hurts recall. So a few fillers may help, and a lot of them don’t.
So should you remove them from your videos?
Here the science stops and judgement starts. The research suggests that natural speech is full of fillers and that listeners cope with them well. But a recording is different from a conversation. People watching a video can’t interrupt, they can easily leave, and they often hear the same sentence only once. Many speakers also dislike how they sound, and studies of how audiences judge hesitant speakers tend to find they are seen as less sure of themselves.
A sensible approach is the one the research points to: don’t aim for zero. A few well-placed fillers sound human. A long run of them, or a pause of several seconds while you find the next point, is what loses people. Cut those, and leave the rest.
Where erm fits
This is why erm shows you every cut before anything is saved. It finds the ums, erms, uhs and long pauses in your video, and you decide which to keep. Words that are sometimes real, like “so” or “you know”, are left alone unless you ask. Everything happens on your Mac, and nothing is uploaded. If you’d rather do it by hand, our guide to removing ums from a video on a Mac shows how.
Sources
- Clark, H. H. & Fox Tree, J. E. (2002). Using uh and um in spontaneous speaking. Cognition, 84(1), 73–111.
- Schachter, S., Christenfeld, N., Ravina, B. & Bilous, F. (1991). Speech disfluency and the structure of knowledge. Journal of Personality and Social Psychology, 60(3), 362–367.
- Corley, M., MacGregor, L. J. & Donaldson, D. I. (2007). It’s the way that you, er, say it: Hesitations in speech affect language comprehension. Cognition, 105(3), 658–668.
- Fraundorf, S. H. & Watson, D. G. (2011). The disfluent discourse: Effects of filled pauses on recall. Journal of Memory and Language, 65(2), 161–175.
- Muhlack, B. et al. (2021). A partial replication of Fraundorf & Watson (2011) in English and German.
Questions
Why do people say um and uh?
Speakers use fillers like “um” and “uh” to buy time while they plan what to say next. The harder the choice of words, the more fillers tend to appear.
Is saying um a sign of nervousness?
Not mainly. Research links fillers more to thinking effort and open-ended choices than to anxiety. Lecturers in subjects with more room for choice say more of them.
Do filler words ever help?
A little. Studies found that a filler can prepare listeners for an unexpected word and that a few can help them remember a story, but too many hurt.
erm is coming soon to the Mac App Store. First 3 videos free, then $29.99 once or $19.99 a year.