Chain ShiftsThe greatest difficulties for speech recognition are posed not by mergers but by chain shifts of vowels. Over the past two decades, two major patterns of chain shifting have been identified, which rotate the vowels of English in opposite directions (Labov, Yaeger & Steiner 1972, Labov 1990, Labov 1994). To examine these, I will draw upon the 220 speakers for whom complete acoustic analyses are now available. The first chain shift is the Northern Cities Shift, shown in Figure 1 below.

The Northern Cities Shift is found throughout the industrial inland North and most strongly advanced in the largest cities: Syracuse, Rochester, Buffalo, Cleveland, Toledo, Detroit, Flint, Gary, Chicago, Rockford. The shift begins when /æ/, the vowel of cad, moves to the position of the vowel of idea /i'/ (1). The vowel /o/ in cod then shifts forward so that it sounds like cad to speakers of other dialects (2). /oh/ in cawed moves down to the position formerly occupied by cod (3), /e/ in Ked moves down and back to sound like the vowel of cud (4), /cud moves back to the position formerly occupied by cawed (5), and /i/ in kid moves back in parallel to the movement of /e/ (6).
A more concrete view of the Northern Cities Shift can be obtained from Chart 1/Rochester. The chart shows the F1, F2 measurements of the six vowels involved for Sharon K., a 35-year old woman from Rochester, NY. The mean value for each vowel is displayed in a white circle. In Sharon K.'s speech stages 1-5 of the shift have gone to completion. (1) Short /æ/ has moved from lower front to high front position, while (2) short /o/ has moved forward to the position vacated by /æ/, and (3) long open /oh/ has moved down to the position vacated by /o/. At the same time, short /e/ has moved down and back until it is positioned in low central position, directly above /o/, while wedge, the vowel of cut has moved back to the position vacated by /oh/.
To assess the effects of the Northern Cities Shift, it may be helpful to compare the relative positions of the vowels involved for two advanced representatives of the shift with two speakers who are quite remote from its influence. Figure 2 displays the normalized means of five short vowels and /oh/. The two Southern speakers, from Springfield, Missouri and Greenville, South Carolina, show the short front vowels vertically aligned, and wedge somewhat front of short /o/, which is in low back position, not far from /oh/. Below them are two Detroit speakers, mother and daughter, who show a developed and advanced stage of the Northern Cities Shift. Here /æ/ has risen to upper mid front position, considerably fronter than short /i/, and /e/ has fallen to mid central position. For Leslie R., /e/ is still to the front of /o/, but for the daughter, Janice, the fronting of /o/ and the further backing of /e/ has led to what is almost a vertical alignment. At the same time, wedge has moved back and /oh/ down, so that it is now directly above /oh/.

Figure 2. Normalized means of the vowels involved in the Northern Cities Shift for two Southern and two Northern speakers.
On the other hand, the Southern Shift, found throughout the Southern States, South Midland, and many other areas, moves vowels in an opposite direction. The shift begins when /ay/ becomes monophthongized and shifts slightly to the front (1). The nucleus of the diphthong /ey/ then falls along a non-peripheral track until it becomes the lowest vowel in the system (2). The nucleus of the diphthong /iy/ follows a parallel path towards mid-center position (3). The short front vowels /i, e/ shift forward and up until they reach the front peripheral positions formerly occupied by /iy/ and /ey/, and /æ/ moves in parallel (4). The nuclei of /uw/ and /ow/ then shift forward to front and center positions (5,6). /ohr/ (now most often merged with /owr/ ) moves up to high back position (7), and /ahr/ shifts up and back to the position that /ohr/ vacated (8).
The operation of the Southern Shift is illustrated in detail in Chart 2/Birmingham , which shows the relevant vowels in the normalized system of Thelma M. from Birmingham, Alabama. In this doubly linear plot, the vertical dimension is the first formant, which corresponds roughly to phonetic height, and the horizontal dimension is the second formant, which corresponds roughly to fronting and backing of the vowel. The individual vowel tokens are plotted with colored symbols, and the means as black and white circles. The key to each vowel token is given at the right: the vowels that are actually plotted are shown with lettering in reverse. In Chart 2/Birmingham, the schematic view of the Southern Shift in Figure 3 is shown as it actually realized. The three short front vowels, /i/, /e/, /æ/ have retained their vertical organization, and have moved up and to the front, in a peripheral position. On the other hand, the long vowel /iy/ in be and the long vowel /ey/ in made have shifted down and to the center along a centralized, non-peripheral track. The /ey/ vowel now has a low nucleus, extending down to overlap to a considerable extent with /ay/, which is monopthongized to [a:]. The back vowels /uw/ and /ow/ have moved strongly to the front, while /ahr/ and /ohr/ show an upward chain shift in the back.
The Northern Cities Shift and the Southern Shift are both complex relations of 6 to 10 vowels. One of the goals of the Telsur project is to derive a small set of numerical parameters which can place each speaker's system within the overall configuration of the regional dialects of North America in a way that reflects both geographic and linguistic regularities. Two such parameters will be presented here: æ/e reversal and e/o alignment.They are designed primarily as measures of participation in the Northern Cities Shift, but they also isolate Southern systems, since the movements of the Southern Shift are diametrically opposed to movements of the Northern Cities Shift.