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And you always thought it was a poor performance from guilty children offering explanations and lame coworkers who weren’t prepared for presentations. But it turns out there’s a scientific reason people tend to “um” and “uh,” and researchers have determined that it’s sometimes dead useful. (No one’s going to tell you it’s not annoying though.) Uh, how does that work? We’ll quit hemming and hawing and lay it out here.

Um, How Do Inane Words Guide Conversation Again?

Basically, if a conversation was a herd of sheep, you would be the shepherd and “um” and “uh” would be the border collie. In other words, they’re valid tools people use to control the flow when they talk. In days gone by, though, business speakers, in particular, used to work hard to stop using filler words.

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But recent findings from the Max Planck Institute for Psycholinguistics indicate “ah” and “you know?” and the like have their place in everyday speech and learning situations. According to research published in the Journal of Memory and Language in March 2019, listeners may not love drawn-out “Ums” or “You know?” added to every sentence uttered. But they do understand what’s coming next when someone uses that phrase, and they adjust their expectation based on whether the speaker is talking in a way they’re familiar with or using atypical speech patterns.

The Planck Institute researchers based their research on earlier work. Linguists at Stanford Univesity and University of California at Santa Cruz concluded almost two decades ago that these seemingly random blurts are actually a form of shared cultural literacy. Speakers use them to signal and listeners pick up the message from those two-letter utterances. While they may seem like subconscious tics to drive the co-conversant mad, “uh” and “um” actually save time by warning of an imminent break in the speaker’s train of thought.

This saves time and smoothes the conversation. “Speakers can use these announcements in turn to implicate, for example, that they are searching for a word, are deciding what to say next, want to keep the floor, or want to cede the floor,” the researchers wrote.

Know What I Mean When I Say ‘Um’?

Plank psycholinguist Hans Rutger Bosker and his team delved deeper on the function of these pausing words, which linguists call “disfluencies.” They found that listeners not only pay attention to “uhs” and “ums,” they adjusted their expectations based on what type of talker was making the sound. The researchers used eye-tracking technology and corresponding images flashed on a computer screen to help them determine if study subjects were paying attention to disfluency and when.

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One of the pictures displayed on the screen was fairly ordinary, the second not so much. Then the subjects listened to both typical and atypical speakers, who either used an “um” ahead of an uncommon word (which is typical) or in front of a common word (which people aren’t used to). The study noted that the subjects quickly adjusted their anticipation of what was to follow based on which type of speaker they were listening to when the disfluency popped in.

When “Uh” Is Spoken With An Accent

Another huge finding from the study: If people spoke with a foreign accent and then used a disfluency ahead of an uncommon word, the subjects adjusted their expectations as usual. But if the person speaking with an accent didn’t have predictable speech patterns and hesitated ahead of an ordinary word, the subjects never altered their expectations. According to co-author Geertje van Bergenthe in the researchers‘ press release, this may mean the listeners had concluded the non-native speaker was struggling with stating even the ordinary words. “So listeners likely took the odd ‘ums’ and ‘ahs’ as unreliable cues for what kind of word might be coming up next,” Bergenthe said.