Words like “um” and “er” tend to have a bad reputation, but a new study suggests that they might actually do listeners a favor.

Researchers at the University of Edinburgh and the University of Stirling in the U.K. measured brain activity to assess listeners’ understanding. Immediately after a person hears words, brain activity spikes downward. In the study, the larger the spike, the more difficult it was for the listener to put the words into context.

The scientists measured these spikes in 12 people after they heard four combinations of sentences: with either predictable or unpredictable target words at the end and with or without “er” uttered right before the target. They found that an “er”—especially when heard before an unpredictable word—shrunk the brain activity spikes of listeners, suggesting this syllable helped subjects place words in context more easily.

Afterward, the scientists tested the subjects to see which target words they remembered best. “Words that were preceded by this disfluency were more likely to be accurately recognized later,” says Martin Corley, a professor at Edinburgh and one of the study's authors. Although the scientists are not sure why the “er” aids listener comprehension and memory, it may warn listeners that something unexpected is coming up.