Ask someone from Cleveland what they think they talk like, and they might tell you, “I don’t thenk I hee-av an ee-accent.” Ask someone from Syracuse, Chicago, or Madison the same question and you might get the same response. Obviously, they do have an accent, but it goes past just being a simple regionalism. It’s part of another well-established linguistic phenomenon, called the Northern Cities Vowel Shift.

The Northern Cities Vowel Shift, or just Northern Cities Shift, has significance beyond just sounding odd to some ears. It marks an unexpected change among North American dialects, and vowel sounds in the English language generally. As one may expect, many American accents are shifting closer together, an effect generally attributed to mass communication, mandatory primary education, and increased mobility and migration within the nation.

But starting in the 60s, linguists started noticing a change in the way people in inland northern cities stretching from upstate New York to Wisconsin pronounced short vowels, starting with the change of the short a, the sound in cat or bat. The sound moved up, that is, the tongue moved higher in the mouth when saying it. Some tensing also took place, making the noise more nasal. Then the sound became more and more diphthongized, sounding in some areas like the last part of idea. From there, a domino effect took place: short vowel sounds kept morphing, falling into the place left behind by another shifted sound. Wis-kawn-son became Wis-keahn-sin, can became kin, job became jab, bus became boss, bell became bull. The result is somewhat reminiscent of Sarah Palin’s accent.

Take the words caught and cot, for instance. Most of the country pronounces those words identically, but inland Northerners often pronounce them differently, keeping a sort of wha noise for caught and leaving cot the way the rest of the country says it. With the Northern Cities Shift, cot took the short a sound and caught moved into cot’s place.

At the forefront of research into this phenomenon is University of Pennsylvania linguistics professor William Labov. “This area used to be the closest to network pronunciation. It was what the NBC standard was based on. And today it is moving further and further away,” Labov said in the documentary Do You Speak American?

The Northern Cities Shift startled linguists for several reasons: first, it came in an area of the country that used to be the standard for American accents–as professor William Labov said in the documentary Do You Speak American? Second, it was a change in vowel sounds that hadn’t changed in centuries. The last major change in vowels (the Great Vowel Shift) began in the twelfth century, but that was a shift in long vowel sounds. Short vowel sounds haven’t changed much since about the eighth century. Additionally, people who speak this way seem especially unaware that they’re doing anything differently. Of course, most people don’t hear their own accents, but NCVS speakers are surprisingly unaware. When played recordings of NCVS speech, many speakers don’t even understand the word they’re hearing or recognize it as different from the way others would say it. “There’s just an incredible deafness to the local pronunciation,” said Dennis Preston, a professor of perceptual linguistics at Oklahoma State University, in a Slate article. “They believe that they are standard, normal, ordinary speakers, and when they’re confronted with evidence to the contrary, they reject it. They reject it in their daily lives, and they reject it even experimentally. They don’t even understand themselves.”

Another surprising element of NCVS is the group who speaks it: while most regionalisms don’t have clearly defined boundaries, NCVS is spoken by a fairly set group of people in a fairly set area. In cities, not rural areas, surrounding the Great Lakes, by mostly white people, and mostly liberals or Democrats, according to Labov, although that may not have a causal link. Most shocking may be the linguistic divide between speakers in these cities and those in cities just a few hours away in Canada. The difference between a speaker from Detroit, Michigan and one just over the bridge in Windsor, Ontario is striking.

Many Americans think NCVS speech sounds bizarre, more like a mispronunciation than an accepted regional shift. In reality, NCVS marks the diversity of North American English. Minnesota falls right on the edge of NCVS territory, and its effects are only just beginning to creep into the language. Generally, only the first few steps in the chain (the change in the short a vowel) can be heard in a Twin Cities speaker, and not for everyone. Still, NCVS keeps spreading–recently, it has begun creeping into St. Louis, which has long been considered a sort of linguistic island, although some argue that the shift is different there or that it may be retreating. Minnesota, of course, has its own accent (Upper Midwest American English, sometimes typified by the monophthongal long o sound) independent of NCVS, which was popularized in the 1996 movie Fargo. Even so, NCVS still seems to be spreading. Who knows, maybe inland north will become the national standard once again–or should I say agan?