Vowel assimilations

[alice]

Adding vertical vowel systems to my Yonagu submission got me thnking. In these systems a given vowel phoneme will typically assimilate in backness to adjacent consonants; we can imagine, for example, /a/ becoming /o/ before labials and /e/ before dentals.

If we assume that a vowel can be affected by preceding and following consonants, and all other things being equal, would the preceding consonant have more influence than the following, or vice versa, or neither?

[AnTeallach]

Adding vertical vowel systems to my Yonagu submission got me thnking. In these systems a given vowel phoneme will typically assimilate in backness to adjacent consonants; we can imagine, for example, /a/ becoming /o/ before labials and /e/ before dentals.

If we assume that a vowel can be affected by preceding and following consonants, and all other things being equal, would the preceding consonant have more influence than the following, or vice versa, or neither?

In one example of a vertical vowel system, Marshallese, the description on Wikipedia suggests that the both consonants have equal influence, and that if they conflict the vowel becomes a diphthong.

http://en.wikipedia.org/wiki/Marshalles ... age#Vowels

[linguoboy]

In Modern Irish, Ó Siadhail describes the language as having a vertical system for the short vowels. With a handful of exceptions (e.g. cuid, scoil), the frontness of a vowel is determined by the quality of the following consonant, with +pal yielding +front, e.g.cnoc ['kn̪ˠʊk] "hill" (nom. sing./gen. pl.) vs. cnoic ['kn̪ˠɪc] (nom. pl./gen. sing.).