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Title:Yoruba vowel patterns: deriving asymmetries by the tension between opposing constraints
Authors:Douglas Pulleyblank
Abstract:Yoruba vowel patterns:

deriving asymmetries by the tension between opposing constraints

Douglas Pulleyblank

University of British Columbia

This paper re-examines a class of pervasive asymmetric properties in the

vowel system of Yoruba. Pulleyblank (1988) argues that high vowels in

general and [i] in particular exhibit a special array of properties. For

example, certain rules of assimilation and deletion are triggered by all

vowels except high vowels. Other rules of assimilation target only high

vowels. In loan vocabulary, [i] is the epenthetic vowel in non-

assimilatory contexts. In Yoruba, as in numerous other cases in the

literature, the recurrence of a particular feature as a conditioning or

nonconditioning factor in various processes can be interpreted as an

argument in favour of underspecified representations (Pulleyblank 1988).

If [-high], [+back], etc. are structurally present in Yoruba vowels, but

[+high] and [-back] are not, then the cited facts receive an explanation.

When assimilation fails to be triggered by [i], this is due to the

absence of features specified for that vowel. When only [i] is targeted

by a rule, this is because the rule is structure-building, not

structure-changing. The epenthesis of [i] is analysed as syllabically-

motivated insertion of a featureless prosodic vowel.

While resolving a number of problems, an underspecified approach raises

others. Clements & Sonaiya (1990) argue that a rule of L Nasalisation

makes crucial reference to [+high], as does a Morpheme Structure

Constraint; Akinlabi (1993) makes a similar argument for a rule of

r-deletion. Such patterns that reference [+high] are incompatible with

an underspecified analysis of the Yoruba vowel system. Note in

particular that certain rules requiring reference to [+high] apply very

early (e.g. as a morpheme structure condition) while certain rules

behaving asymmetrically apply very late (e.g. a rule of vowel deletion

that crosses word boundaries). The apparent conflict in behaviour cannot

be resolved, therefore, by assuming an early stage of underspecification

followed by a subsequent stage of more complete specification.

Of particular interest to the treatment of asymmetric phonological

behaviour, both the paper by Clements & Sonaiya and the paper by

Akinlabi reinforce the asymmetric nature of high vowels, each presenting

additional data of a special asymmetric nature. Hence even though the

underspecification approach appears to fail, if we accept their

arguments then it becomes even more important therefore to find a

theoretical account that can satisfactorily account for the asymmetries

in the Yoruba vowel system.

This paper discusses three possible analyses for Yoruba. First, it lays

out the possibility that there are no special asymmetries at all, that

the particular properties of any individual construction are due to

idiosyncratic properties of individual rules. Second it examines the

possibility that asymmetries are significant and due to a structural

property such as underspecification. Third, it explores the possibility

that asymmetric behaviour results from the relative ranking of

constraints. That is, the special properties of high vowels result not

from structural encoding, but from the ranking of constraints on high

vowels above and below constraints implicated in particular

constructions. It is shown that both rule-governed and underspecified

accounts require special stipulations of an ad hoc nature as additional

constructions are considered, where the constraint-based approach does

not. The general conclusion is that a constraint-based approach resolves

the problems raised by the analyses of Clements & Sonaiya and Akinlabi,

as well as other problems intrinsic to the proposal of underspecification.

The paper therefore constitutes an argument in favour of the encoding of

asymmetries in a constraint grammar rather than in elaborated structures.

In developing the treatment of asymmetric behaviour, harmonically ranked

sonority constraints play a central role. The paper argues that such

reference to sonority must be encoded directly into the expression of

the faithfulness constraints, rather than through an independent set of

well-formedness conditions. That is, the paper argues for the encoding

of "sonority as faithfulness".
Type:Paper/tech report
Article:Version 1