Despite globalization of film and television, the Internet, world-wide telephone capabilities, and continual travel, we aren't losing distinct regional speech. In fact, linguists say American dialects are actually diverging and thriving.
In a story at Slate, Rob Mifsud writes that 34 million people in cities that ring the Great Lakes are revolutionizing the sounds of the English language. Linguists began noticing a change in the articulation of vowel sounds in those cities in the 1960s, Mifsud writes, and in 1972, three linguists led by William Labov of the University of Pennsylvania called the phenomenon the Northern Cities Shift (NCS). Lebov thinks it may be the most important change in the last thousand years. Think you know how to say caught, cot, cat, bet and but? There's no right or wrong, but it will sound different depending on where you live. Linguists aren't sure about reasons for the changes, and no one is sure how they will evolve.
Labov thinks the new trend may be rooted in the multiply accented versions of English that immigrants brought to the region when they came to build the Erie Canal in the late 1800s. Linguists think NCS began with a change in the way people move their tongues to produce a short "a" sound. As Labov explains, "language is a set of connected items," and that causes all the other vowels to move around "something like a game of musical chairs." So people in Detroit work at a jab, not a job, they roll out the cat, not the cot, for a guest to sleep on, and ride home on a boss rather than a bus. And some flat As, as in flat, grow another syllable, as in "fleaht."
Today's English speakers would need extensive study to comprehend the language of Chaucer. The larger Great Vowel Shift that brought about the modern pronunciations of A, E, I, O and U, began about 1400, and the sounds remained pretty stable for centuries. Until now. In his writing and lectures, the linguist John McWhorter talks about the how language continually changes-eroding, re-growing and emerging, as words shift in meaning, structure, usage and sound, in ways we rarely realize at the time.
Dennis Preston, a linguistics professor from Oklahoma State University noticed when he was teaching in Michigan that NCS speakers there were oblivious to their own distinctions of speech. Mifsud describes an experiment in which NCS speakers hearing a list of words spoken by a person with NCS accent could not distinguish between cat and cot. His story explains that to Preston, the reasons are that people think their own speech is standard and normal, and they reject evidence to the contrary: "They reject it in their daily lives, and they reject it experimentally. They don't even understand themselves."
Allan Metcalf writes in the Chronicle of Higher Education that a traditional eastern New England accent, in which the "r" after a vowel is dropped, as in "New Hampsha," is becoming less common. In New Jersey, some people have "cawfee before wawking the dawg," but some listeners say there the line between a south Jersey and north Jersey accent is shifting. Visit the International Dialects of English Archives to hear samples of speech from each state. Listen to Lebov here.