Vowels

In discussing the vowel patterns, we begin with the elements considered essential as points of departure for the phonological analysis of North American English dialects, according to Labov (1991: 21). The lack of a merger between low, back, unrounded /a/ (LOT) and mid, back, rounded, lengthened  (THOUGHT) and the behavior of low front /æ/ (TRAP/BATH) as a unified phoneme (rather than split into tense and lax classes) is seen as essential conditions for the Northern Cities Chain Shift (NCCS), a major ongoing change in American phonology. The presence of these two phonemic patterns is necessary for the onset of the NCCS: TRAP/BATH raises, leaving a space for LOT to move forward and maintain its distinction from THOUGHT (Boberg 2001: 11; Labov 1994: 184; Gordon, this volume), thus initiating a chain shift.