The Low-Back-Merger Shift is a chain shift of vowel sounds found in several dialects of North American English, beginning in the last quarter of the 20th century and most significantly involving the low back merger accompanied by the lowering and backing of the front lax vowels:,, and .
The back and downward movement of all the front lax vowels was first noted as distinguishing certain California English speakers in 1987,[1] and it was soon known by linguists as the California Vowel Shift. Then, it came to distinguish certain Canadian English speakers in a 1995 study,[2] now known in that variety as the Canadian Shift; today, it helps define Standard Canadian English. The California and Canadian Shifts were initially reported as two separate phenomena, but the same basic pattern was next documented among some younger varieties of Western New England English, Western American English, Pacific Northwest English, and Midland American English, all in speakers born after 1980.[3] Linguists have proposed possible relationships between the low back merger and the similarly structured shifts in these regional dialects, though no unifying hypothesis is dominantly agreed upon yet.[4] Assuming the similar chain shifts found in Canada and various parts of the U.S. have a single common origin, a variety of names have been proposed for this trans-regional chain shift which, besides the low-back-merger shift, include the Third Dialect Shift, Elsewhere Shift, Short Front Vowel Shift, and North American Shift.
Aside from the Low-Back-Merger Shift characterizing these North American varieties, similar, though not identical, shifts to the short front vowels are also attested in other English dialects globally as of 21st-century research,[5] including modern Received Pronunciation,[6] Indian English,[7] Hiberno-English,[8] South African English,[9] and Australian English[10] (the last two dialects traditionally defined by a chain shift moving in the opposite direction of the Low-Back-Merger Shift). These changes outside of North America particularly intrigue linguists as they lack the vowel configuration presumed to initiate this shift: the low back merger.
The Canadian Shift involves the lowering of the tongue in the front lax vowels pronounced as //æ// (the short-a of trap), pronounced as //ɛ// (the short-e of dress), and pronounced as //ɪ// (the short-i of kit).
It is triggered by the cot–caught merger: pronounced as //ɑ// (as in cot) and pronounced as //ɔ// (as in caught) merge as pronounced as /[ɒ]/, a low back rounded vowel.[11] As each space opens up, the next vowel along moves into it. Thus, the short a pronounced as //æ// retracts from a near-low front position to a low central position, with a quality similar to the vowel heard in Northern England pronounced as /[a]/. The retraction of pronounced as //æ// was independently observed in Vancouver[12] and is more advanced for Ontarians and women than for people from the Prairies or Atlantic Canada and men.[13] pronounced as //æ// also retracts more before /l/ than other consonants. In Toronto, /æ/-retraction is inhibited by a following nasal, but it is not in Vancouver.[14]
However, scholars disagree on the behaviour of pronounced as //ɛ// and pronounced as //ɪ//:
Due to the Canadian Shift, the short-a and the short-o are shifted in opposite directions to that of the Northern Cities Vowel Shift, found across the border in the Inland Northern U.S. and Western New England,[19] which is causing these two dialects to diverge: the Canadian short-a is very similar in quality to the Inland Northern short-o. For example, the production pronounced as /[map]/ would be recognized as map in Canada but mop in the Inland North.
In the United States, the cot-caught merger is widespread across many regions of the United States, particularly in the Midland and West, but speakers with the merger are often not affected by the shift, possibly due to the fact that the merged vowel is less rounded, less back and slightly lower than the Canadian vowel. This means that there is less space for the retraction of the vowel pronounced as //æ//, which is a key feature of the Canadian shift. However, there are many regions of the United States where the Canadian shift can be observed, and this is often more closely linked to the raising or retraction of pronounced as //ɑ//, rather than the actual low back merger.
The California Vowel Shift in progress in California English contains features similar to the Canadian Shift, including the lowering/retraction of the front lax vowels. However, the retraction of pronounced as //æ// has happened in California even though the Californian pronounced as //ɑ// may be more centralized and not as rounded as the Canadian pronounced as //ɒ//, leading some scholars suggest that the two phenomena are distinct,[20] while others suggest that it was backed "just enough" to allow the shift to happen.[21] Within speakers, the retraction of pronounced as //æ// is more correlated with the raising of pronounced as //ɑ// than with the low back merger.[22]
See main article: Western American English. The Atlas of North American English finds that, in the Western United States, one out of every four speakers exhibits the Canadian Shift, as defined quantitatively by Labov et al. based on the formant values for pronounced as //æ//, pronounced as //ɑ//, and pronounced as //ɛ//. More recent data, however, suggests that the shift is widespread among younger speakers throughout the West.
Stanley (2020)[23] found evidence of the shift in Cowlitz County, Washington, where the formant trajectories of pronounced as //æ//, pronounced as //ɛ//, and pronounced as //ɪ// flattened, causing the onset of pronounced as //æ// to lower and slightly retract, the onset of pronounced as //ɛ// to lower and retract, and the onset of pronounced as //ɪ// to retract. However, the speakers in the study tended to pronounce pronounced as //ɑ// and pronounced as //ɔ// "close" but distinct, with pronounced as //ɔ// being further back and more diphthongal. Furthermore, this state of near merger had persisted for all 4 generations in the study. An explanation for this is that while the merger itself was not the trigger for the shift, the backing of pronounced as //ɑ// leading to the near-merger of pronounced as //ɑ// and pronounced as //ɔ// was the trigger.[24]
See main article: Midland American English. Durian (2008)[25] found evidence of the Canadian shift in the vowel systems of men born in 1965 and later in Columbus, Ohio. This is located in the U.S. Midland. The Midland dialect is a mix of Northern and Southern dialect features. In Columbus, pronounced as //ʌ// is undergoing fronting without lowering, while still remaining distinct from the space occupied by pronounced as //ɛ//. At the same time, historical pronounced as //ɒ// (the vowel in "lot") is merged with the pronounced as //ɑ// class, which is raising and backing towards pronounced as //ɔ//, such that the two are merged or "close". This allows a "free space" for the retraction of pronounced as //æ//, which is also suggested as a possibility for Western U.S. dialects by Boberg (2005). In Columbus, the Canadian shift closely resembles the version found by Boberg (2005) in Montreal, where pronounced as //ɑ// and pronounced as //ɔ// are either merged or "close", and pronounced as //æ//, pronounced as //ɛ//, and pronounced as //ɪ// show retraction of the nucleus without much lowering (with pronounced as //æ// also showing "rising diphthong" behavior). However, the retraction of pronounced as //ɪ// was not found among all speakers and is more mild among the speakers that do show it than the retraction of pronounced as //ɛ// among those speakers. Additionally, the outcome of low back merger-like behavior is more like the California shift outcome noted above than the rounded variant found in most of Canada.
See main article: Western Pennsylvania English. In Pittsburgh, another region where the cot-caught merger is prevalent, the mouth vowel pronounced as //aʊ// is usually a monophthong that fills the lower central space, which prevents retracting. However, as pronounced as //aʊ// monophthongization declines, some younger speakers are retracting pronounced as //æ//.
See main article: Inland Northern American English. As noted above, the first two stages of the Northern Cities Shift (NCS) move pronounced as //æ// and pronounced as //ɑ// in the exact opposite direction of the Canadian Shift. However, the NCS is gaining stigma among younger speakers,[26] which can trigger the lowering of pronounced as //æ// and the backing of pronounced as //ɑ//. In fact, Savage et al. (2015)[27] found that, while the raising of pronounced as //æ// and fronting of pronounced as //ɑ// are stigmatized, the lowering and backing of pronounced as //ɛ//, a feature of both shifts, is considered prestigious. Nesbitt et al. (2019) say that the Canadian shift may be replacing the NCS.[28]
Jacewicz (2011)[29] found the shift in parts of Wisconsin, where, despite the NCS, pronounced as //æ// is lowered and backed, and pronounced as //ɑ// raises, backs, and diphthongizes to approach pronounced as //ɔ//, although, like in Columbus and in Cowlitz County, the merger is not actually complete for most of the speakers in the study, and the lowering of pronounced as //æ// is more linked with the raising of pronounced as //ɑ//. In addition, pronounced as //ɛ// is lowered and backed which is in alignment with both the NCS and the Canadian shift.
Jacewicz (2011) also found evidence for the shift in parts of North Carolina, where the vowels pronounced as //ɪ//, pronounced as //ɛ//, and pronounced as //æ// lower and monophthongize, undoing the Southern U.S. Shift. pronounced as //ɑ// raises, backs and diphthongizes to approach pronounced as //ɔ//, although the low back merger is not complete for any of the speakers in the study.
In the ANAE, the speech of Atlanta, Georgia is classified as a typologically Midland dialect because it had already lacked the monopthongization of pronounced as //aɪ//. However, it appears that the monopthongization of pronounced as //aɪ// was a feature of Atlantan speech in the early 20th century, and that much younger speakers have undone the reversal of the front lax and tense vowels that is part of the Southern shift, retracted pronounced as //ɪ//, pronounced as //ɛ//, and pronounced as //æ//, and have a near merger pronounced as //ɑ// and pronounced as //ɔ//.[30]
See main article: New York City English and New York accent. In New York City, there is evidence of the lowering and retraction of pronounced as //æ// (except before nasals),[31] pronounced as //ɛ//, and pronounced as //ɪ//[32] particularly among younger non-white speakers. This is despite the fact that Traditional New York City English has an opaque split of the /æ/ phoneme; younger speakers are increasingly lowering pronounced as //æ// before voiceless fricatives and voiceless stops and raising it before all nasals. This also correlates with retraction of pronounced as //ɑ// and the lowering of pronounced as //ɔ//, but not necessarily with the low back merger.