Parents never want their tots to learn to fumble over words, but they need not worry about their own “uhs” and “ums”—­such filled pauses may actu­­ally improve kids’ ability to pick up language.

Such vocal hesitations, called dis­fluencies, tend to occur before we use a word that is infrequent or unfamiliar in our speech. They also precede words used for the first time in a conversation. Disfluencies keep adults tuned in and help them process the real words that come next.

Even infants can distinguish between fluent and disfluent speech, research at Brown Univer­sity has shown. New experiments at the University of Rochester suggest that around the age of two, children make an association between the disfluencies they hear and the likelihood that new words will follow them.

In the study, kids aged 16 to 32 months sat on their parent’s lap in front of a computer monitor that showed images of paired objects, one recognizable (such as a ball) and one imaginary but equally colorful.

The first time a pair appeared, a voice from the computer said, “I see the ball.” The second time it said, “Ooh, what a nice ball.” The third time it instructed the children to look at one of the objects in the pair, using a made-up word for the invented object such as “gorp.”

During this third step, some­times the voice said simply, “Look! Look at the ball,” or “Look! Look at the gorp.” In other trials, the sentence included a disfluency: “Look! Look at the, uh, ball,” or “Look! Look at the, uh, gorp.”

When kids heard the disfluency, they paid significantly more attention to the unfamiliar object for the next two seconds—before the computer finished the sentence with either “ball” or “gorp.” During the “fluent” trials, when the com­puter did not say “the, uh,” the children were no more likely to fixate on one object over the other.

The results suggest that disfluencies help kids follow a conversation, says Celeste Kidd, a graduate student who co-authored the study (published online in April in the journal Developmental Science). “We don’t know whether they’re reasoning about the speaker’s intentions, which is a pretty sophisti­cated understanding, or whether they just notice an association between ‘uh’ and ‘um’ and objects they don’t know the name of,” she says.

Either way, parents can relax and speak normally, ums and all—what seem like verbal stumbles are actually useful signals that tell youngsters to tune in.