, the green dots represent speakers who have completely merged the vowels of cot
and caught''. The dark blue dots represent speakers who have completely resisted the merger. The medium blue dots represent speakers with a partial merger (either production or perception but not both), and the yellow dots represent speakers with the merger in transition. The presence of the merger and its absence are both found in many different regions of the North American continent, where it has been studied in greatest depth, and in both urban and rural environments. The symbols traditionally used to transcribe the vowels in the words
cot and
caught as spoken in
American English are and , respectively, although their precise
phonetic values may vary, as does the phonetic value of the merged vowel in the regions where the merger occurs. Even without taking into account the mobility of the American population, the distribution of the merger is still complex; there are pockets of speakers with the merger in areas that lack it, and vice versa. There are areas where the merger has only partially occurred, or is in a state of transition. For example, based on research directed by
William Labov (using telephone surveys) in the 1990s, younger speakers in
Kansas,
Nebraska, and the
Dakotas exhibited the merger while speakers older than 40 typically did not. The 2003 Harvard Dialect Survey, in which subjects did not necessarily grow up in the place they identified as the source of their dialect features, indicates that there are speakers of both merging and contrast-preserving accents throughout the country, though the basic isoglosses are almost identical to those revealed by Labov's 1996 telephone survey. Both surveys indicate that, as of the 1990s, approximately 60% of American English speakers preserved the contrast, while approximately 40% merged the phonemes. Further complicating matters are speakers who merge the phonemes in some contexts but not others, or merge them when the words are spoken unstressed or casually but not when they are stressed. Speakers with the merger in northeastern New England still maintain a phonemic distinction between a fronted and unrounded (phonetically ) and a back and usually rounded (phonetically ), because in northeastern New England (unlike in Canada and the Western United States), the
cot–
caught merger occurred without the
father–
bother merger. Thus, although northeastern New Englanders pronounce both
cot and
caught as , they pronounce
cart as . Labov et al. also reveal that, for about 15% of respondents, a specific – merger before but not before (or other consonants) is in effect, so that
Don and
dawn are homophonous, but
cot and
caught are not. In this case, a distinct vowel shift (which overlaps with the
cot–
caught merger for all speakers who have indeed completed the
cot–
caught merger) is taking place, identified as the '''
Don–
dawn merger'''.
Resistance According to Labov, Ash, and Boberg, the merger in North America is most strongly resisted in three regions: • The "
Inland North", encompassing the eastern and central Great Lakes region (on the U.S. side of the border) • The "
Northeast Corridor" along the Atlantic coast, ranging from Baltimore to Philadelphia to New York City to Providence. However, the merger is common in Boston and further northern New England. • The "
South", somewhat excluding Texas and Florida. In the three American regions above, sociolinguists have studied three phonetic shifts that can explain their resistance to the merger. The first is the fronting of found in the Inland North, in which the vowel is advanced as far as the cardinal (the
open front unrounded vowel), thus allowing the vowel to lower into the phonetic environment of without any merger taking place. The second situation is the raising of the vowel found in Providence, New York City, Philadelphia, and Baltimore, in which the vowel is raised and diphthongized to , or, less commonly, , thus keeping that vowel notably distinct from the vowel .
African-American Vernacular English accents have traditionally resisted the
cot–
caught merger, with pronounced and traditionally pronounced , though now often . Early-2000s research has shown that this resistance may continue to be reinforced by the fronting of , linked through a
chain shift of vowels to the raising of the , , and perhaps vowels. This chain shift is called the "African American Shift". However, there is still evidence of AAVE speakers picking up the
cot–
caught merger in
Pittsburgh, Pennsylvania, in
Charleston, South Carolina, in Florida and Georgia, and in parts of California.
Origin In North America, the first evidence of the merger (or its initial conditions) comes from western Pennsylvania as far back as the data shows. From there, it entered
Upper Canada (what is now
Ontario). In the mid-19th century, the merger also independently began in eastern New England, In Canadian English, further westward spread was completed more quickly than in English of the United States. Two traditional theories of the merger's origins have been longstanding in linguistics: one group of scholars argues for an independent North American development, while others argue for contact-induced language change via
Scots-Irish or Scottish immigrants to North America. In fact, both theories may be true but for different regions. The merger's appearance in western Pennsylvania is better explained as an effect of Scots-Irish settlement, but in eastern New England, and perhaps the American West, as an internal structural development. Canadian linguist
Charles Boberg considers the issue unresolved. A third theory has been used to explain the merger's appearance specifically in northeastern Pennsylvania: an influx of Polish- and other Slavic-language speakers whose
learner English failed to maintain the distinction. ==Scotland==