Modish public speaking coaches will tell you that it's OK to say "uh" or "um" once in a while, but the prevailing wisdom is that you should avoid such "disfluencies" or "discourse particles" entirely. It's thought that they repel listeners and make speakers appear unprepared, unconfident, stupid, or anxious (or all of these together). Perhaps the biggest foe of "uh" and "um" is Toastmasters International, which charges speakers a nickel for every "filled" pause (that is, for every pause that's not silent). Each of their 12,500 clubs around the world has an official "ah" counter.
But "uh" and "um" don't deserve eradication; there's no good reason to uproot them. People have been pausing and filling their pauses with a neutral vowel (or sometimes with an actual word) for as long as we've had language, which is about 100,000 years. If listeners are so naturally repelled by "uhs" and "ums," you'd think those sounds would have been eliminated long before now. The opposite is true: Filled pauses appear in all of the world's languages, and the anti-ummers have no way to explain, if they're so ugly, what "euh" in French, or "äh" and "ähm" in German, or "eto" and "ano" in Japanese are doing in human language at all.
In the history of oratory and public speaking, the notion that good speaking requires umlessness is actually a fairly recent, and very American, invention. It didn't emerge as a cultural standard until the early 20th century, when the phonograph and radio suddenly held up to speakers' ears all the quirks and warbles that, before then, had flitted by. Another development was the codification of public speaking as an academic subject. Counting "ums" and noting perfect fluency gave teachers something to score.
What's more, "uhs" and "ums" do not necessarily damage a speaker's standing. Recently, a University of Michigan research team turned their attention to phone survey interviewers. They found that the most successful interviewers—the ones who convinced respondents to stay on the line and answer questions—spoke moderately fast and paused occasionally, either silently or with a filler "uh" or "um." "If interviewers made no pauses at all," the lead researcher, Jose Benki, told Science Daily, "they had the lowest success rates getting people to agree to do the survey. We think that's because they sound too scripted." Speaking with a certain number of "uhs" and "ums," it seems, may actually enhance a speaker's credibility.
(Get more stories like this one delivered to your inbox. Please sign up here for Slate's daily newsletter.)
Blithely unaware of the evidence, some parents—call them linguistic tiger moms—strive to keep filled pauses out of their kids' mouths. In April, Sarah Groves wrote an essay in the Christian Science Monitor about training her children to be umless. Her son was torturing her with questions like, "That man, um, not Hector, um er that man, not Paris, um, that man, not ..." After discussing the situation with her husband ("I want to love them by teaching them to be articulate"), she told her son, "Before you speak you must think, 'This is what I'm going to say,' and then when you start to speak you mustn't think about anything else except what you decided you were going to say. Then you say it, quick and clear, with no um's and no er's." Apparently the 5-year-old mastered umlessness in two days.
Yet studies suggest that "uh" and "um" play an active role in how we learn language and communicate. A University of Rochester lab published a paper this spring showing that kids over 2 were more likely to pay attention to an unfamiliar object if the speaker said "uh" before stating its name. Presumably, this tactic gives children a leg up on parsing an adult's speech. Take the example of the mother who says to her child, "No, that wasn't the telephone, honey. That was the, uh, timer." The "uh" indicates that there's a word coming up that might be new and unfamiliar, so extra attention is required.
Of course, "uh" and "um" don't have some magic monopoly on focusing a listener's attention. In a study published in PLoS ONE last May, Martin Corley and Robert J. Hartsuiker reported that listeners' recognition benefits from any delay before a word, whether it's a silent pause, a filled pause, or a musical tone. The delay "attunes the attention."
In the Rochester study, kids under 2 didn't respond to "uh" at all—they didn't seem to tune out or tune in—which probably means they hadn't yet learned to interpret "uh" as a clue to adults' intentions. The authors suggest this ability appears at some point in the second year. They don't say anything about when kids start to say "um," which must happen on a different time line, because my 20-month-old son recently uttered his first. Given my fascination with filled pauses, it was a happy day, and I considered sending out greeting cards to celebrate the accomplishment.
The momentous exchange went something like this: