'Raising' of unstressed vowels in English

[Roger Lass]

----------------------------Original message----------------------------
A couple of points.

1. This phenomenon is not at all uncommon in English across the world. To
take one example of a fairly typical sort, my own New York City dialect has
[I] before /t, d/ in weak syllables (e.g. weak pasts and past participles),
and often before velars as in 'communicate'. Impressionistically, what is
*not* common is to have a 'schwa' type of vowel in these environments, at
least in England and the eastern US. One of the more striking low-level
phonetic characters of much South African English is precisely the lack of
two weak vowels of different heights.

2. The existence of a higher weak vowel especially before coronals has been
attested as a regularity in southern and South Midland English dialects
since late Middle English. Chaucer for instance apparently rhymes the
regular noun
plural in /-Vs/ with 'is', and it is common later Middle English MS practice
to spell this ending with
<i, y> rather than <e>. My impression (needs checking, but this is a quick
answer) is that <i> spellings for noun plural are rather late: the earliest
example I've found in a quick look at the samples in the corpus for the
Linguistic Atlas of Early Middle English currently being prepared in
Edinburgh is from the Lambeth Homilies (c. 1200). If anybody is interested I
can run a more detailed check, and it would be worth looking at the sections
on unstressed vowels in these environments in some of the more detailed
histories of English.