BOSTON HAS SEEN a dramatic increase in its Hispanic population since 2000, over 25 percent according to census records. That’s left an obvious and significant mark on the way locals speak English — but the city’s Spanish is also evolving, according to forthcoming research from Boston University linguist Daniel Erker.

Erker’s paper focuses on pause fillers, those tiny unconscious blips of sound, “um” or “uh” in English. What he’s found is that, as the city’s Spanish-speakers study English and come into contact with different varieties of their own language, filled pauses are evolving — part of what Erker thinks could be a new Bostonian Spanish, a way of speaking that’s consistent across nationalities but distinct from the Spanish spoken in Miami or New York or Chicago. Erker’s research, although still preliminary, suggests how much this phenomenon could resemble regional dialects in English — while making another argument for the power of the humble pause filler.

Pause fillers were long dismissed as stumbles or informal ways of stalling for time. Over the past few years, though, linguists have become far more interested in their subtle and varied functions. Pause fillers — which University of Pennsylvania linguist Mark Liberman says should be more appropriately called “hesitation phenomena” due to their wide-ranging applications — can be used to hold a place in conversation, to interrupt, to introduce a thought, or even to communicate something about what’s being introduced. Liberman uses the example of former New York mayor Ed Koch’s radio talk show. Koch would often introduce himself, “This is Ed, uh, Koch.” This wasn’t a verbal stumble or a sign that Koch was forgetting his own surname. “The only point was to emphasize what came after,” i.e., Koch’s last name, Liberman said.

Across many languages, pause fillers often bear a broad family resemblance: French has “euh,” Welsh “ym,” Russian “ah.” Most of the Germanic languages use versions of “um” and “uh,” according to Liberman, who has studied the preference for “um” over “uh” among women and young people across those languages. Spanish-speakers, meanwhile, most frequently fill pauses with “eh” or “em” or “ah.”

The “schwa” sound that you hear when you say “uh” or “um,” and which is written in the phonetic alphabet as an upside-down “e,” is the most common vowel sound in English — but it doesn’t exist in Spanish at all. After looking at 1,600 pause fillers used by a group of 24 native Spanish-speakers from across Latin America, Erker concluded that the longer they’d been in Boston, the closer their “eh” approached the schwa of “uh”/“um,” stopping along the way at “ah,” a sound that’s phonetically in between “eh” and “uh.”

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