For all three speakers, /, , / lie in a row across the non-peripheral upper edge of the vowel space, each different from the other. This is evidence that the proper form of phonological schwa is //, a short, central, high vowel.
For all three speakers, the non-low short vowels, /, , , /, are centralized and lowered, relative to their long counterparts /iy, ey, uw, ow/; the back vowels are not centralized (fronted) as much as the front vowels are centralized (backed). Note that for Rita and Judy, who have a fronted /uw/ and //, this effect takes the form of lowering, since these nucleus are high-central. The only exception to this rule is Rita's // which is not significantly lower than her /ow/. Apparently Rita is not participating in the lowering of // in the Northern Cities Chain Shift.
This data therefore provide fairly strong support for the the generalization that the non-low short vowels are centralized and lowered relative to the corresponding long nuclei. This generalization is quite similar to the relationship between long and short vowels in Jamaican Creole, formalized in rules 4, 7, pages , . Rule (7), which states that the short vowels are lowered relative to the long vowels, cannot be a universal fact, since Rita's // is not lower than the corresponding long vowel, /ow/. In fact, the nuclei of long vowels may be identical with those of their short counterparts, as are, for example, /ey/ and // in the Alabama speaker's vowel system (see Figure , page ).