In chain shifts, tense nuclei rise along a peripheral track.
Principle II
In chain shifts, lax nuclei fall along a nonperipheral track. (176)
Principle II applies to the series shown above in (1) for tense vowels which become lax/nonperipheral and are then lowered. Additionally, according to Labov (1994, 210), the lax front vowels tense, moving to the peripheral track, or the outside envelope of acoustic vowel space. They may then rise, following Principle I. The front vowels are therefore affected by two subshifts, or minimal chain shifts, and together are considered an extended chain shift (Labov 1994, 118-119).
On the other hand, the back vowels are involved in their own subshift, which is may be called a “parallel” shift since there are no vowels moving in to take their places. Following Principle III of Chain Shifting – “In chain shifts, back vowels move to the front” (Labov 1994,116) – the back vowels move forward in phonetic space. Labov et al. (1972, 124) remark
The paths of /ow/ and /uw/ do not make up a chain shift: they are parallel movements responding to some common cause. It is not at all obvious that a chain shift is involved in this situation, since there seems to be no back
upgliding vowel which moves up behind /uw/ and /ow/ to assume their positions and which might have been held back by /uw/.
Figure 1 displays the phonetic changes to American English phonemes that may occur due to the Southern Shift as it might occur in Alabama. While much literature on the SVS simplifies the complex movement of the front vowels by emphasizing the relative rotation of the pairs of high vowels and mid vowels, the nuclei of the tense vowels in both tense-lax pairs actually fall quite far; the high vowel becomes/approaches a mid vowel, the mid vowel becomes/approaches a low vowel.
u
i ʊ
ɪ
e
o
ɛ ɔ
(?)
æ a: [ɑi] (ɑ)
Figure 1.1 Vowel Shifting in the Southern Shift
Figure 1.1 illustrates the movements within acoustic space that are associated with the SVS (after Labov 1994, 209 and Labov, Yeager, and Steiner 1972, 132, 146). The nucleus of /e/ (which is, in reality, usually diphthongal [eɪ] in American English) tends to be backed and lowered so that it approaches the sound of (ay) tokens in Standard English. For example, weighed in shifted speech may sound more like wide. In some areas, /i/ may also back and may additionally lower. In the areas where both of these occur, weed might sound similar to weighed. As mentioned above, movement of the nucleus of (ay) is considered to be the first stage of the SVS. Stage 2 is the relative rotation of the mid front vowels (the tense/lax pair). Stage 3 is the relative rotation of high front vowels (Labov, Ash, and Boberg 2006, 125-127). There is some discrepancy in findings on the behavior of the front low vowel /æ/, but it is often not included in depictions of the SVS and, since it is not one of the SVS features designated for this study, I will not cover the debate here. The back vowels /u/, /ʊ/, and /o/ also move forward in acoustic space. Quite frequently, /u/ tokens are pronounced with such a fronted vowel that they overlap with space for /i/ (e.g., Labov, Yaeger, and Steiner 1972, 145). The forward shifting back vowels are not included as a feature in this study. In general, incorporating at least one vowel affected by the SVS is a valuable addition to the perceptual survey, useful for ascertaining which features listeners believe evoke a more Southern sound.