Vowel reduction degrades information in phonology and the speech signal
Vowel reduction degrades phonetic information in the speech signal and should be understood as having an analogous impact on phonological representations. More generally, informational asymmetries in the speech signal should be viewed as mapping to informational asymmetries in phonology. The point is illustrated by analyses of vowel reduction in a variety of languages drawn from Bantu, Romance and Slavic.
Reduction follows two apparently contradictory routes in vowel space, yielding either centralised vowels (the 'centripetal' pattern) or the corner vowels [a, i, u] (the 'centrifugal' pattern). Recently this divergence has been attributed to constraints that bring conflicting pressures to bear on vowels in weak syllables: some call for prominence to be reduced, others for contrasts to be enhanced (Crosswhite 2001).
However, vowel reduction emerges as a unitary phenomenon if we take account of its effects on the phonetic-informational content of speech signals. The spectral profiles of schwa and the corner vowels can be viewed as less complex than those of mid peripheral vowels. Centripetal and centrifugal reduction thus have the shared effect of diminishing the amount of phonetic
information in the speech signal.
In selectively targeting weak nuclei to the exclusion of strong, reduction has the effect of enhancing syntagmatic contrast. If informational asymmetries of this sort are to be directly recorded in phonological representations (and there's no reason to suppose they shouldn't), it is
necessary to abandon certain standard assumptions about the design of feature theory.
