Traditionally, "uh" and "um" were thought to be involuntary products of a momentary difficulty in processing what one wants to say, or in deciding whether one actually wants to say it, and therefore are meaningless themselves. Alternatively, they were seen as merely a means of preventing people from interrupting during a pause in speaking. There's an obvious problem with this view, though. Why do we have more than one such marker of disfluency? In fact, English isn't the only language with more than one. Clark and Fox Tree1 found equivalents of both "uh" and "um" or similar fillers in multiple languages, including Japanese, Spanish, Norwiegan, Swedish, Dutch, French, German, and Hebrew. Distinct elements with no differences rarely survive in a language, much less several languages from different families, so there must be something to "uh" and "um."
Clark and Fox Tree conducted several studies using data from both laboratory experiments and the London–Lund corpus of British English, and concluded that "uh" and "um" have all the properties required to be a words in English:
- Phonetics: They have distinct sounds.
- Prosody: "When placed within intonation units, hey are normally delivered with a parenthetical intonation, a monotone pitch that allows them to be segregated from the melody of the surrounding construction" (p. 104). In other words, we have distinct ways of speaking them relative to the words around them.
- Syntax: Well, according to Clark and Fox Tree, they're interjections, like "like," or "oh!" so they don't really have associated syntactical rules.
- Semantics: They have distinct meanings.
Subsequent research has found that "uh" and "um" may have even more specific meanings. For example, using an eye-tracker (an apparatus that monitors where on a screen a participant is looking), Arnold et al2 found that participants who heard "uh" while listening to speech referring to objects on a screen immediately looked to objects that had not yet been mentioned. So it seems that "uh" not only signals a pause, but more importantly, tells the listener that the speaker is about to refer to something new, or as a later study by Arnold and colleagues found3, to something unfamiliar.
Further evidence suggests that it may not just be new, but also important things that "uh" and "um" signal. Collard et al3 found that after listening to speech that referred to several different objects, participants given a surprise memory test were more likely to remember having heard words that were preceded by "uh" or "um" than words that weren't, suggesting that when they heard "uh" or "um," they devoted more attention to what came next.
There is mounting evidence, then, that "uh" and "um" are more than just involuntary veral tics. Instead, they seem to carry meaning, signalling a pause and perhaps that something new, unfamiliar, or important is about to be said. Researchers are still trying to sort these things out, though, and there are still open questions. For example, Finlayson and Corley5 have shown that people are equally likely to use "uh" and "um" in monologues and dialogues, suggesting that, while they may convey information to listeners, speakers may not intentionally use them to do so. I look forward to learning how such questions are answered by future research, though. If nothing else, I will learn more about why I say "um" so much so that I can explain it to my son when he asks me to stop.
1 Clark, H.H., and Fox Tree, J.E. (2002). Using uh and um in spontaneous speaking. Cognition, 84, 73-111.
2 Arnold, J.E., Tanenhaus, M.K., Altmann, R.J., and Fagnano, M. (2004). The old and thee, uh, new: Disfluency and reference resolution. Psychological Science, 15(9), 578-582.
3 Arnold, J.E., Hudson Kam, C.L., and Tanenhaus, M.K. (2007). If you say thee uh you are describing something hard: The on-line attribution of disfluency during reference comprehension. Journal of Experimental Psychology: Learning, Memory, and Cognition, 33(5), 914-930.
4 Corley, M., MacGregor, L.J., and Donaldson, D.I. (2007). It's the way that you, er, say it: Hesitations in speech affect language comprehension. Cognition, 105, 658-668.
5 Finlayson, I.R., and Corley, M. (2012). Disfluency in dialogue: an intentional signal from the speaker? Psychonomic Bulletin and Review, 19(5), 921-928.