YORUBA VOWEL PATTERNS: ASYMMETRIES THROUGH PHONOLOGICAL COMPETITION*

Douglas Pulleyblank 1 Introduction The analysis of Yoruba vowels has been the focus of several papers and has been a topic in numerous others. But while this body of work has led to a clear description of a wide variety of phenomena, it has also raised a number of prob-lems of both analytic and theoretical interest. The core issue to be addressed here arises out of such work. Various patterns have been described that identify a range of special properties for high vowels in general and [i] in particular (e.g. Bamgbos ¢e 1965, Awobuluyi 1978, 1992, Pulleyblank 1988a, Owolabi 1989, etc.). In an attempt to account in a principled fashion for the special status ac-corded the high vowels, the analysis of these patterns was proposed in Pulley-blank 1988a to depend on a fundamental structural property, underspecification of the high front vowel. While successful for a certain range of data, subsequent work demonstrated the inadequacy of the underspecification hypothesis (Clements & S¢onaiya 1990, Akinlabi 1993). There has been no account, how-ever, succeeding in integrating accounts of the diverse range of phenomena into a unified analysis.

A close examination of the argument against underspecification makes it clear that the overall issue of how to treat Yoruba vowels remains open. The problem is this. Asymmetric behaviour of high vowels necessitates some sort of special treatment. Underspecification was one possibility. When problems with an underspecified analysis of Yoruba were raised, the problems were not with the data patterns – it was agreed that high vowels were special – rather, the prob-lems were with the underspecified analysis. Indeed, papers such as Clements & S¢onaiya (1990) and Akinlabi (1993) showed that high vowels were special in still more ways, but that their special properties could not be accounted for by the device of underspecification. The problem of how to replace an underspeci-fied account by a more adequate account was left open. This paper proposes to resolve that problem.

The development of an adequate theory of natural language depends cru-cially on integrating comprehensive analyses of individual languages with an understanding of cross-linguistic patterns. This paper constitutes a case-study of a class of vocalic patterns in Yoruba, attempting such integration. The central problem is how to account for a range of processes where vowels behave in an asymmetric fashion. Specifically, high vowels in general and the vowel [i] in

* Thanks to John Alderete, Constance Cummings, Laura Downing and Philip Mutaka for

comments on a draft of this paper. This work was supported by a grant from the Social Sciences and Humanities Research Council of Canada.

2 Pulleyblank

particular are frequently distinguished in Yoruba by their phonological behav-iour (Pulleyblank 1988a). 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 (Salami 1972). Liquids become nasals before the vowel [i] (Clements & S¢onaiya 1990). The consonant [r] deletes adjacent to a high vowel (Akinlabi 1993). The large number of such cases argues againt viewing them as accidental. At issue, therefore, is how to account for the special properties of the high vowel class in general and the high front vowel in particular.

Two basic types of treatments for this type of asymmetry have been dis-cussed in the recent literature. The underspecification approach referred to above is representational. If vocalic representations are asymmetric through the underspecification of one value for each feature, then in the Yoruba case non-high vowels could be overtly specified for height and the special properties of high vowels could be attributed to an absence of phonological specification for height. The singular properties of the vowel [i] would be the result of being to-tally unspecified for vocalic features. As will be shown, however, the under-specified representational approach is problematic on both conceptual and em-pirical grounds, leading one to seriously consider a second option based on con-straint interaction. In a number of papers within Optimality Theory (Prince & Smolensky 1993, McCarthy & Prince 1993a, Casali 1996, Alderete et al 1999, etc.), it has been suggested that there are harmonically ranked constraints on fea-tural markedness and that the interaction of these constraints with other con-straints can result in skewed patterns of phonological distribution and alterna-tion. According to this view, vowels can exhibit very special behaviour without the postulation of any special representational properties.

I argue for the view based on constraint interaction in this paper. Specifi-cally, I suggest that a scale of vocalic markedness results in certain processes preferentially applying to nonhigh vowels, other processes preferentially apply-ing to high or high front vowels, and still other processes exhibiting symmetrical behaviour of both high and nonhigh vowels. The proposal accounts for a wider range of data from Yoruba than possible in previous accounts, and does so by the adoption of a constraint scale based on cross-linguistic observations about intrinsic vowel sonority. 2 The analytic core: regressive and progressive assimilation This section presents the basic analysis of vocalic asymmetries. In laying out the proposed analysis, two overall goals should be kept in mind. First, the proposed analysis targets cases involving patterns of vowel distribution and alternation, examining symmetrical and asymmetrical behaviour. Second, the proposed analysis locates itself within a larger research program examining Yoruba pho-nology. In a series of papers (O ¢la Orie & Pulleyblank 2002, Howe & Pulley-

Yoruba vowel patterns 3

blank 2004, Pulleyblank in press), an internally consistent analysis of a large body of Yoruba data is attempted, focussing on vowels.

I begin by considering patterns of feature assimilation that occur when two vowels are brought into contact with each other in a noun phrase.1 Canoni-cal nouns of Yoruba are VCV in structure. There is a genitive construction, “N of N”, where two nouns occur without any overt intervening genitival marker, making it possible to observe a sequence of adjacent vowels. In this configura-tion, it is typical for assimilation to cause the …V1 ][V2… sequence to surface as a sequence of identical vowels.2

Where the second vowel (V2) in the sequence is nonhigh, it will normally prevail in such a situation, resulting in a …V2 ][V2…surface pattern.3 (1) Regressive feature assimilation; second vowel is nonhigh ..NONHI] [NONHI.. a. owo! ade! [owo! ade!] [owa! ade!] ‘money of Ade’ b. owo! epo [owo! ekpo] [owe! ekpo] ‘money of oil’ c. o¢mo¢ e¢ran [O)mO) Er˛)a)] [O)mE) E)r )̨a)] ‘goat-kid; son or a bitch’ d. e¢~ro¢ owo! [E~rO owo!] [E~ro owo!] ‘near the river’ e. e¢~ba! odo~ [E~ba! odo~] [E~bo! odo~] ‘near the river’ f. ara! o¢~run [ara! O~r )̨u)] [arO! O~r )̨u)] ‘citizen of heaven; masquerader’ ..HI] [NONHI.. g. omi e¢ran [om )̧ Er)a)] [omE) E)r)a)] ‘water of meat’ h. or¸ !̨ ade! [or¸ !̨ ade!] [ora! ade!] ‘Ade’s head’ i. or¸ !̨ o~jo! [or¸ !̨ o~Ôo!] [oro! o~Ôo!] ‘Ojo’s head’

In contrast, when the second vowel is high, then it is replaced by the preceding vowel.

1 These data have been discussed in some detail in the literature; the reader is referred to

work such as Awobuluyi (1978), Pulleyblank (1988a), Awoyale (to appear) for additional examples and discussion. Assimilation is not restricted to the noun phrase, as shown with the non-contracting verb ku! in (2f), but noun phrases present a large illustrative class for assimilation. See footnote 2.

2 Why this type of vowel contact situation results in assimilation rather than deletion is a matter orthogonal to the concerns of this paper. Following O¢la Orie & Pulleyblank (2002), I assume a basic analysis whereby each noun independently satisfies a condition on pro-sodic minimality. As such, deletion would result in prosodic deterioration while assimila-tion respects minimality.

3 Yoruba data are presented in standard orthography as well as in a broad phonetic tran-scription. Relevant orthographic conventions are as follows: e¢ = [E], o¢ = [O], Vn = nasa-lised vowel (Yoruba syllables never have codas), s¢ = [S], p = [k°p], acute ( !) = H, grave ( ~) = L, unmarked for tone = M.

4 Pulleyblank

(2) Progressive feature assimilation; second vowel is high front ..NONHI] [HI FRONT.. a. ile! is¢e¢! [ile! iSE!] [ile!eSE!] ‘place of work’ b. ara! ¸ ~̨lu! [ara! ¸ ~̨lu!] [ara!a~lu!] ‘townsman’ c. owo! ile! [owo! ile!] [owo!ole!] ‘money of house; rent’ ..HI BACK] [HI FRONT.. d. e¢ru~ igi [Eru~ igi] [Eru~ugi] ‘bundle of wood’ e. igun ile! [igu) ile!] [igu)u)le!] ‘corner of house’ f. ku! is¢e¢! [ku! iSE!] [ku!uSE!] ‘greetings at work’

Three factors must interact in the analysis of these forms. First, some con-

straint must trigger assimilation. Second, some ‘general’ constraint must ensure that it is normally the first vowel in the sequence that deletes. Third, a ‘special’ constraint must cause high vowels to be targeted by assimilation wherever they occur. While it is the third constraint that is of particular interest here, the con-straint involving high vowels can only be understood in the general context of vowel interactions.

As in O ¢la Orie & Pulleyblank (2002) and Pulleyblank (in press), I assume that a constraint against vowel hiatus is the motivating factor behind assimila-tion: it is ill-formed to have adjacent vowels linked to different sets of features.

(3) NOHIATUS

Where hiatus potentially results from the juxtaposition of two words, assimila-tion resolves the vowel contact problem.

(4) Sequences of nonhigh vowels NOHIATUS /owo! ekpo/ a. [owo! ekpo] *! b. � [owe! ekpo]

NOHIATUS by itself, however, does not resolve the issue of which vowel

survives the assimilation process. Casali (1996, 1997) has demonstrated that the predominant pattern cross-linguistically is for V1 to delete in a V1 V2 sequence. To derive the general pattern of regressive assimilation, I assume that left-edge anchoring is crucial. Since satisfaction of NOHIATUS requires the loss of a root node, assimilation causes a disruption in correspondence at one edge of a mor-pheme or the other. Building on work by Prince & Smolensky (1993) and

Yoruba vowel patterns 5

McCarthy & Prince (1993b, 1995),4 deletion of V1 results in misalignment at the right edge of the morpheme (the right edge of the input morpheme does not align with the right edge of the output morpheme), while deletion of V2 results in misalignment at the left edge of the morpheme (the left edge of the input mor-pheme does not align with the left edge of the output morpheme).

(5) ANCHORL: Any root node at the left edge of a morpheme in the input has a

correspondent root node at the left edge of the morpheme in the output.

ANCHORR: Any root node at the right edge of a morpheme in the input has a correspondent root node at the right edge of the morpheme in the output.

Since the normal pattern is one of V2 retention, the optimal output must respect correspondence at the left edge of the morpheme: ANCHORL must outrank ANCHORR.

Consider again the case of /owo! ekpo/ ~ [owe! ekpo].

(6) Sequences of nonhigh vowels: the role of anchoring NOHIATUS ANCHORL ANCHORR a. [owo! ekpo] *! /owo! ekpo/ b. [owo! okpo] *! c. � [owe! ekpo] *

If the [e] of [ekpo] deletes, then left-edge correspondence of [ekpo] is disrupted (6b). If the final [o] of [owo!] deletes, then right-edge correspondence is dis-rupted (6c). By ranking left-edge correspondence above right-edge correspon-dence, the observed surface form is achieved.

A couple of observations are relevant concerning anchoring. First, McCarthy and Prince (1995) make the point that a minimally stipulative analysis of reduplication ought to utilise for reduplication the same class of constraints as motivated elsewhere for nonreduplicative phenomena (see also Pulleyblank in press). Depending on whether “anchoring” can be successfully equated with “alignment”, anchoring has been a potential problem in this regard in that its motivation appeared to be primarily within the realm of reduplication. Here, an-choring plays a nonreduplicative role. The need for such nonreduplicative an-choring therefore supports the use of anchoring in reduplication. Second, build-ing on Casali (1996, 1997), I consider that ANCHORL is harmonically ranked

4 See also Blake (1998) on St’at’imcets.

6 Pulleyblank

above ANCHORR.5 For on-line processing, it is important to be able to locate stems in order to access lexical items. Frequently, indeed typically, lexical ac-cess is achieved prior to arrival at the right edge of a lexical item. As such, dis-ruption at the left edge of a form will inhibit lexical access, whereas disruption at the right edge will in many cases have no serious effect since lexical access has already been achieved. For discussion, see Cutler, Hawkins & Gilligan (1985), Hall (1992). For the remainder of this paper, ANCHORL will be included in relevant tableaux, while ANCHORR will be excluded since it is not ranked highly enough to play a crucial role in the phenomena under consideration.6

The constraint grammar considered so far would systematically result in regressive assimilation. While this is indeed the general case, we may now ad-dress the special cases involving the high front vowel [i], where a V i sequence results in progressive assimilation. The core of the proposal made here is to con-sider a nonhigh or back nucleus as more harmonic than a high front nucleus (Prince & Smolensky 1993). Assuming that the relevant harmonic evaluation is feature-based, we need an analysis where nonhigh vowels are more harmonic than high vowels, and back vowels are more harmonic than front vowels. Since there appear to be no relevant distinctions in Yoruba between nonhigh vowels, I assume the three classes shown in (7).

5 Casali (1996) proposes that positional faithfulness to initial position universally outranks

general faithfulness. Since deletion of a morpheme-initial vowel would cause a violation of such positionally restricted faithfulness while deletion of a morpheme-final vowel would not, retention of V2 over V1 is observed in a V1##V2 sequence.

6 Lamontagne & Rosenthall (1996) discuss the general preference for retention of V2 over V1 in V1##V2 sequences, and argue that the preferential retention of V2 derives principally from constraints on contiguity. In particular, ‘juncture contiguity’ requires that two seg-ments that are adjacent in the input be adjacent in the output when they abut across a syl-lable boundary. Relating to input /owo ekpo/, a candidate such as [o.woo.kpo] violates juncture contiguity while [o.wee.kpo] satisfies it. Whatever its general merits, such an ac-count does not give the desired results for Yoruba. First, such an account depends on mo-tivating deletion/merger/coalescence by syllable well-formedness constraints. This is problematical in Yoruba; see O¢la Orie & Pulleyblank (2002). Second, such an account does not account for morpheme-internal cases such as /agogo/ ~ [aago] seen in section §6. Junctural integrity would be violated by the actually occurring surface form [aa.go] but would be satisfied by the nonoccurring *[oo.go]. As a general point, note that the junctural contiguity proposal predicts a distinction between deletion/merger/coalescence in open vs. closed syllables. With an input like /te abo/ where V2 is open, deletion should optimally result in [ta.bo] if junctural contiguity is highly ranked: [te.bo] violates junctural contigu-ity, [ta.bo] does not. In contrast, if V2 is part of a closed syllable, then junctural contiguity is irrelevant. For an input like /te ambo/, both [tem.bo] and [tam.bo] respect junctural con-tiguity. The choice between the two would therefore default to other constraints, which Lamontagne and Rosenthall show would favour V1 retention. Hence it would be possible for the input /te abo/ to result in [ta.bo] but /te ambo/ to result in [tem.bo].

Yoruba vowel patterns 7

(7) Harmonic vowel classes NONHI ™ HI BACK ™ HI FRONT a, o, O, e, E u i A B C

This scale is straightforwardly interpreted as a scale of relative sonority.7 While the precise factors relevant for the assessment of relative sonority in vowels are not universally agreed upon, assuming that “openness” is a fundamental crite-rion is standard. Typical scales range therefore from the prototypically open vowel [A] at the most sonorous end of the scale to the fully closed plosives [p, t, k…] at the least sonorous end. Relative openness in vowels of different heights has led numerous researchers to establish a vowel scale where low vowels are the most sonorous, high vowels are the least sonorous, and mid vowels have an intermediate value (Jespersen 1904, Selkirk 1984, Blevins 1995, Kenstowicz 1997, etc.). Introducing finer distinctions into the scale, work such as Hooper (1976) and Foley (1977) proposes that back round vowels are more sonorous than front vowels. In a similar fashion, Jones (1918) and Pike (1943) consider [i] as less sonorous than [u].8 Adopting the proposal that a sonority scale is an ag-gregate derived from the intersection of component scales (e.g. Foley 1977, Steriade 1982), we can derive the scale in (7) by the intersection of a scale rank-ing nonhigh vowels over high vowels and a second scale ranking back vowels over front ones. To derive the lack of differentiation in Yoruba between nonhigh vowels, I assume following Prince & Smolensky (1993) that subparts of a har-monically ranked scale can be collapsed and encapsulated.9 Hence the potential ranking of nonhigh back vowels as more harmonic than nonhigh front vowels plays no role in Yoruba, though it could play a role in other grammars.

Interpreted as a scale for assessing the relative harmony of syllable nuclei (Prince & Smolensky 1993: 16), (7) establishes nonhigh vowels as the best nu-clei, high back vowels as the next best, and high front vowels as the least good.

7 At a presentation of a much earlier version of this paper, Armin Mester suggested to me

that I try replacing structural underspecification with reference to sonority differences. To a significant extent, the current state of this paper represents my attempt to do just that.

8 De Lacy (2002) argues that a difference between ‘peripheral’ and ‘nonperipheral’ vowels should be factored into the sonority scale, but that the front-back distinction should not. He argues, for example, that inclusion of the front-back dimension would predict unat-tested patterns of stress placement. I leave unresolved the problem of reconciling the Yoruba pattern with the sorts of cases that he discusses.

9 See de Lacy (2002) for the proposal that the device of encapsulation should be replaced by the encoding of constraints stringently.

8 Pulleyblank

(8) HNUC |x| > |y| ⇒ Nuc/x ™ Nuc/y ‘A higher sonority nucleus is more harmonic than one of lower sonority.’

Since considerations of the harmonic quality of a nucleus over-ride left-edge an-choring, HNUC (along with NOHIATUS) must be ranked above ANCHORL.

(9) NOHIATUS, HNUC >> ANCHORL

For a case such as /owo! ekpo/ ~ [owe! ekpo], seen above in (6), the addi-tion of HNUC will have no effect since the vowels in contact are both nonhigh.

(10) Addition of HNuc to the constraint set NOHIATUS HNUC ANCHORL a. [owo! ekpo] *! …Nonhi Nonhi… /owo! ekpo/ b. [owo! okpo] Nonhi *! c. � [owe! ekpo] Nonhi

When the second word begins with a high front vowel, however, the pres-

ence of HNUC forces assimilation to be progressive. For example, /ile iSE/ as-similates to [ile†eSE] (with progressive assimilation) rather than to *[ili iSE] (with the otherwise expected regressive assimilation).

(11) Vowel sequences where V2 is high

NOHIATUS HNUC ANCHORL a. [ile! iSE!] *! …Nonhi HiFr… /ile! iSE!/ b. � [ile! eSE!] Nonhi * c. [il¸ !̨ iSE!] *HiFr!

The weakness of the high front vowel can be seen both when adjacent to a non-high vowel, as in (11), and with a high back vowel, as in (12).

(12) Vowel sequences where V1 is high back and V2 is high front

NOHIATUS HNUC ANCHORL a. [eru~ igi] *! …HiBk HiFr… /Eru~ igi/ b. � [eru~ ugi] HiBk * c. [er¸ ~̨ igi] *HiFr!

Attributing the vulnerability of the high front vowel to its low harmonic

status is fundamentally different than attributing such vulnerability to represen-

Yoruba vowel patterns 9

tational underspecification since no special structural representation need be as-sumed for the high front vowel. The scale in (7) is compatible with featural rep-resentations involving either binary or unary features, with features fully or par-tially specified. The crucial point is that nonhigh vowels are more harmonic than high vowels no matter how height is represented structurally, and high back vowels are more harmonic than high front vowels, again without regard for the structural representation. As we will see, this property allows a more compre-hensive account of vocalic phenomena than possible under a structural account.

In the following sections, I illustrate first an additional case where an asymmetric pattern involving high front vowels is accounted for the relative harmony of the nucleus. I go on to show an additional case where problems arise. To account for the problems, it is argued that a unified account of sonor-ity-based behaviour requires that sonority be built into the formulation of faith-fulness rather than assessed independently as pure nuclear harmony. 3 Vowel deletion In cases where vowel contact results from the juxtaposition of a monosyllabic vowel-final word preceding a polysyllabic vowel-initial word, deletion rather than assimilation is observed.10

If the second vowel in the sequence is nonhigh, the first vowel deletes, whether the first vowel is nonhigh (a-f), high back (g-i), or high front (j-l).11

(13) Vowel deletion where V2 (of …V1V2…) is nonhigh

..NONHI] [NONHI.. Careful Regular a. se olu! [se olu!] [solu!] ‘cook mushrooms’ b. je¢ ede! [ÔE ede!] [Ôede!] ‘eat shrimp’ c. jo! e¢~wu~ [Ôo! E~wu~] [ÔE!wu~] ‘burn clothing’ d. ra o¢~ge¢~de¢~ [ra O~gE~dE~] [rO~gE~dE~] ‘buy bananas’ e. gbe! e¢se¢~ [gbe! EsE~] [gbE!sE~] ‘lift leg’ f. je¢ owo! [ÔE owo!] [Ôowo!] ‘win money’

10 There is a large literature on vowel deletion in Yoruba. See, for example, Ward (1952),

Rowlands (1954), Abraham (1958), Siertsema (1959), Bamgbos¢e (1966), Courtenay (1968), Oyelaran (1971), Badejo (1979), Awoyale (1985), Akinlabi & Oyebade (1987), Pulleyblank (1988a,b), O¢la (1991), O¢la Orie & Pulleyblank (2002).

11 Only the main pattern is described here. Much of the literature on Yoruba vowel deletion addresses the fact that there are numerous examples where the second vowel deletes in-stead of the first vowel. Following work such as Akinlabi & Oyebade (1987) and Pulley-blank (1988b), I assume that the general phrasal case is as described in the text, with spe-cial cases of V2 deletion encoded lexically in one way or another. Whatever the account of V1 vs. V2 deletion, there is general agreement that deletion affects the vowel [i] in a way that is different from other vowels.

10 Pulleyblank

..HI BACK] [NONHI.. g. bu omi [bu om¸ )̨] [bom¸ )̨] ‘dip out water’ h. ru o¢~ge¢~de¢~ [ru O~gE~dE~] [rO~gE~dE~] ‘carry bananas’ i. lu agogo [lu agogo] [lagogo] ‘ring a bell’ ..HI FRONT] [NONHI.. j. n¸˛! oko [n¸ )̨⁄ oko] [lo!ko] ‘at the farm’ k. s¸ !̨ o¢ja~ [s¸ !̨ OÔa~] [sO!Ôa~] ‘to the market’ l. j¸ !̨ owo! [Ô¸˛! owo!] [Ôo!wo!] ‘steal money’

In contrast, when the second vowel is high front, it deletes. This is true if

the first vowel is nonhigh (a-c) and if the first vowel in high back (d-f). When both vowels are high front, the segmental result of deletion is of course the same whether one analyses deletion as affecting the first or the second vowel (g-i).

(14) Vowel deletion where V2 (of …V1V2…) is high front

..NONHI] [HI FRONT.. a. gba is¢e¢! [gba iSE!] [gbaSE!] ‘take a job’ b. gbe! ina! [gbe! ina)⁄] [gbe!na)⁄] ‘lift the lamp’ c. wo ile¢~ [wo ilE~] [wolE~] ‘look at the ground’ ..HI BACK] [HI FRONT.. d. ju igi [Ôu igi] [Ôugi] ‘throw a stick’ e. lu ile¢~ [lu ilE~] [lulE~] ‘hit the ground’ f. ru igi [ru igi] [rugi] ‘carry firewood’ ..HI FRONT] [HI FRONT.. g. s¸ !̨ ile! [s¸ !̨ ile!] [s¸ !̨le!] ‘at the market’ h. r¸˛! is¢e¢! [r¸˛! iSE!] [r¸˛!SE!] ‘get work’ i. ti ¸ ~̨le¢~ku~n [ti ¸˛~lE~ku)Ÿ] [t¸˛~lE~ku)Ÿ] ‘shut door’

One pattern is missing in Standard Yoruba, namely the case where the

second vowel is high back. This gap is due to the fact that words in Standard Yoruba can never begin with the vowel [u]. A dialect that allows such forms will be discussed in §8 below.

The analysis of these forms follows straightforwardly. Setting aside for a moment the question of why these forms exhibit deletion rather than assimila-tion, the pattern is entirely comparable to the assimilatory cases of (1) and (2). When two nonhigh vowels come in contact, for example, NOHIATUS rules out the retention of the sequence (15a); deleting either of the nonhigh vowels results in a nonhigh nucleus (15b,c), hence ANCHORL forces selection of the candidate which deletes the first vowel in the sequence (15c).

Yoruba vowel patterns 11

(15) Deletion not involving a high front vowel NOHIATUS HNUC ANCHORL a. [se olu!] *! …Nonhi Nonhi… /se olu!/ b. [selu!] Nonhi *! c. � [solu!] Nonhi

When the second vowel is [i], the situation is different because it is more har-monic to delete [i], even if such deletion results in an anchoring violation.

(16) Deletion involving a high front vowel as V2 NOHIATUS HNUC ANCHORL a. [lu ilE~] *! …HiBk HiFr… /lu ilE~/ b. � [lulE~] HiBk * c. [lilE~] *HiFr!

NOHIATUS continues to render the candidate retaining both vowels as nonopti-mal (16a), but the candidate retaining the most harmonic vowel (16b) wins over the candidate that respects anchoring (16c).

For discussion of what distinguishes the assimilation cases from the dele-tion cases, the reader is referred to O¢la Orie & Pulleyblank (2002). The central idea is that hiatus is optimally resolved via assimilation when foot binarity is re-spected12 but by deletion when binarity is violated. This basic idea can be seen by comparing (17) with (18), where feet are indicated by parentheses. When hia-tus results from the juxtaposition of two words individually satisfying binarity, loss of a vowel would result in a gratuitous violation of FTBIN.

(17) Role of binarity: assimilation optimal /owo! ekpo/ NOHIATUS HNUC ANCHORL FTBIN a. [(owo!) (ekpo)] *! …Nonhi Nonhi… b. �[(owe!) (ekpo)] …Nonhi… c. [(o) (we!kpo)] …Nonhi… *!

In contrast, when a subminimal word abuts an independently minimal word, as-similation by itself would maintain a binarity violation while deletion brings about satisfaction of binarity.13

12 FTBIN: A foot must be binary at either the syllabic or moraic level (McCarthy & Prince

1993, etc.). 13 There are numerous cases of interest with regard to minimality, including various combi-

nations of subminimal and supraminimal words. See O¢la Orie & Pulleyblank (2002).

12 Pulleyblank

(18) Role of binarity: deletion optimal /se olu!/ NOHIATUS HNUC ANCHORL FTBIN a. [(se) (olu!)] *! …Nonhi Nonhi… * b. [(so) (olu!)] Nonhi *! c. � [(solu!)] Nonhi

In conclusion, we see that cases of both assimilation and deletion obey a

two-way imperative. First and foremost, nonhigh and high back vowels are maintained at the expense of high front vowels. Second, when abutting vowels are of comparable sonority, words respect left-edge anchoring.

4 Vowel epenthesis While the patterns of assimilation and deletion seen so far are compatible with a view of sonority where nuclei are assessed by well-formedness conditions on their harmonic status (“HNUC”), additional patterns demonstrate that HNUC is inadequate as an overall strategy for encoding sonority reference. It is argued in this and subsequent sections that a unified treatment requires the encoding of sonority distinctions directly into the expression of faithfulness.

As shown in Pulleyblank (1988a), Yoruba syllable structure forces the ep-enthesis of vowels to avoid codas and consonant clusters. Abstracting away from cases where the epenthetic vowel participates in some type of assimilation causing it to be realised as a back vowel or as identical to an adjacent vowel, data such as (19) show that the epenthetic vowel in unconditioned environments is [i] (see Salami 1972, Pulleyblank 1988a, Akinlabi 1993, Awobuluyi 1997).

(19) Vowel epenthesis in loan incorporation

a. d¸˛!re¢!ba~ [d¸ !̨rE!ba~] ‘driver’ b. s¸ !̨l¸ !̨pa!a~s¸ ~̨ [s¸˛!l¸ !̨kpa!a~s¸ ~̨] ‘slippers’ c. b¸˛!r¸˛!k¸˛~ [b¸ !̨r¸˛!k¸˛~] ‘brick’ d. g¸˛!ra!ma~ [g¸ !̨ra!ma~] ‘grammar’ e. k¸˛!la!a~s¸ ~̨ [k¸ !̨la!a~s¸ ~̨] ‘class’ f. fo¢!o¢~k¸˛~ [fO!O~k¸˛~] ‘fork’ g. s¢e¢!e¢~t¸ ~̨ [SE!E~t¸ ~̨] ‘shirt’ h. ya!a~d¸˛~ [ya!a~d¸˛~] ‘yard’ i. to¢!o¢~s¢¸ ~̨ [tO!O~S¸ ~̨] ‘flashlight’ < torch

As shown in Howe & Pulleyblank (2004), a scale that ranks nonhigh

vowels and high back vowels as more harmonic than high front vowels cannot account for the quality of the epenthetic vowel in such data. Sonority-driven well-formedness would lead one to expect that [a] would be epenthesised in

Yoruba vowel patterns 13

such forms, wrongly identifying a form like *ya!a~da~ (20b) as optimal for a loan-word like ‘yard’ rather than the actually occurring form ya!a~d¸ ~̨ (20d).

(20) HNUC cannot account for the quality of the epenthetic vowel /ya!a~d/ SYLLABLE

CONSTRAINTS HNUC

a. [ya!a~d] *! b. � [ya!a~da~] …Nonhi c. [ya!a~du~] …*HiBk! d. [ya!a~d¸˛~] …*HiFr!

The problem can be easily seen by comparing a form like [gbaSE!]

(*[gbiSE!]) (14a) with [ya!a~d¸˛~] (*[ya!a~da~]) (19i). For the syllable [gba] of [gbaSE!] constraints must evaluate [a] as optimal, while for the syllable [d¸ ~̨] of [ya!a~d¸˛~] constraints must evaluate [i] as optimal. Whether reference is to intrinsic vowel quality, to intrinsic duration, or to some other property, the divergent assessment of the two cases will not be achieved unless there is a mechanism for having dif-fering constraint sets applicable to the two cases.

A conceptually unified approach to the problem is possible by incorporat-ing reference to vowel sonority directly into the class of faithfulness constraints. Standardly, faithfulness constraints require identity between inputs and outputs. The claim made here is that deviations from identity are more or less serious de-pending on the prominence of the segments involved (Jun 1995, Beckman 1997, Casali 1997, Steriade 1999, Zhang 2000, Howe & Pulleyblank 2004, etc.). Loss of a segment or feature from the input is more serious when the loss involves a highly sonorous segment, and less serious when the loss is of a less sonorous segment (MAXIO). The addition of a segment or feature to the output is more serious when the insertion involves a highly sonorous segment, and less serious when the insertion is of a less sonorous segment (DEPIO). The essence of the proposal is that the more salient the loss, the more significant the MAXIO viola-tion; the more salient the epenthesis, the more significant the DEPIO violation. Foley (1977) proposes that phonological processes are subject to a principle of inertia – encoding sonority into faithfulness has this result.

Hence I reinterpret the scale in (7) in terms of a harmonically governed set of feature-based14 faithfulness constraints:15

14 For the relativisation of MAX and DEP to feature-sized units rather than to segments, see

McCarthy & Prince (1995), Lombardi (1995, 1998), Pulleyblank (1996, 1998), Myers (1997), etc.

15 The proposal made here is similar to de Lacy’s proposal that “the more marked an element is, the greater the pressure to preserve it” (2002, p. 1). The analysis presented here differs in numerous respects, however, from that of de Lacy. For example, scalar reference is in-

14 Pulleyblank

(21) Sonority through faithfulness a. Constraint set:

MAX: Every element of the input has a correspondent in the output. DEP: Every element of the output has a correspondent in the input.

b. Assessment of violations: |x| > |y| ⇒ FAITH/x ™ FAITH/y ‘If x is more sonorous than y, then a violation of faithfulness involving x constitutes a bigger violation than a violation of faithfulness involving y.’

Analysed in this way, faithfulness constraints will assign a greater penalty

to the epenthesis of a more sonorous vowel than a less sonorous vowel, correctly deriving the default epenthesis of [i].

(22) Epenthesis of [i] as the minimally sonorous violation of faithfulness /ya!a~d/ SYLLABLE

CONSTRAINTS DEP

a. [ya!a~d] *! b. [ya!a~da~] Nonhi! c. [ya!a~du~] HiBk! d. � [ya!a~d¸˛~] HiFr

In an analogous fashion, this interpretation of sonority-sensitive faithful-

ness will continue to enforce the retention of the most sonorous vowel in cases where vowels of unequal sonority are juxtaposed. To illustrate, consider a tab-leau reinterpreting the case seen above in (16).16

(23) Deletion targets the least sonorous vowel /lu ilE~/ NOHIATUS MAX ANCHORL a. [lu ilE~] *! b. � [lulE~] HiFr * c. [lilE~] HiBk!

Although both (23b) and (23c) violate MAX, the violation in (23c) is more seri-ous as a more sonorous vowel has been deleted. The overall picture is one where

corporated into feature-based MAX and DEP constraints, the sonority scale includes a front-back dimension, and constraints are not formulated stringently. It is beyond the scope of this paper to discuss such differences.

16 Note that NOHIATUS must outrank MAX since all candidates violate one or the other con-straint, and the optimal output violates MAX.

Yoruba vowel patterns 15

if a violation of faithfulness is forced, the least salient violation is optimal. Hence the most sonorous vowel is retained (23) and the least sonorous vowel is introduced (22).

Additional arguments for encoding these sonority-based distinctions di-rectly in the evaluation of faithfulness will be given in §7 below.

5 Interim assessment In this section, I compare the above analysis with rule-based alternatives.

5.1 Assimilation Under a rule-based analysis, a pair of rules is required for progressive and re-gressive assimilation. If fully specified vowels are assumed, then the first rule spreads vocalic place features progressively, under the specific condition that the second vowel in the sequence be [+high]; the second, more general, rule then spreads vocalic place features regressively. (24) Rule-based approach, fully specified vowels

a. Progressive Spread:

b. Regressive Spread: (the elsewhere case)

By ordering the height-conditioned rule before the general rule, the correct pat-terns are obtained.

If underspecified vowels are assumed, then two rules are still required but the actual formulation of the rules is simplified.

(25) Underspecification approach: [i]: unspecified for PLACE vs. [e, E, a, O, o, u]: specified for PLACE

a. Regressive Spread:

b. Progressive Spread: (the elsewhere case)

Regressive Spread now must apply first, but fails to apply when V2 is [i] since [i] has no place specifications. Progressive Spread applies only in those cases (namely with [i]) where Progressive Spread fails.

5.2 Deletion As with assimilation, a rule-based approach to vowel deletion requires two rules. One rule deletes the second vowel in a sequence if the second vowel is [i]; an-other rule deletes the first vowel in a sequence in all other vowel combinations:

16 Pulleyblank

(26) Rule-based approach, fully specified vowels a. High front vowel deletion: [i] � Ø / V ___ b. General vowel deletion V � Ø / ___ V

Crucially, High front vowel deletion must apply before General vowel deletion.

If underspecified representations are assumed, the situation is rather dif-ferent as it is possible to assume a single rule of deletion:

(27) Rule-based approach, underspecified vowels

General vowel deletion V � Ø / ___ V Where both vowels have non-null specifications, the only rule to apply is the general rule of vowel deletion; but where the second vowel is unspecified (i.e. the vowel [i]), then the features of the first vowel manifest themselves on the second position. This could be the result of progressive assimilation (see Pulley-blank 1988b); alternatively it could be the result of autosegmental featural sta-bility, with the place features of the first vowel associating post-deletion to the free mora of the second vowel (illustrated in (28b)). (28) Vowel deletion: with underspecified representations Deletion Reassociation a. Specified vowel

s o l ue

µ1

σ σ σ

µ2 µ3

�

s o l ue

σ σ

µ2 µ3

b. Underspecified vowel

w l Eo

µ1

σ σ σ

µ2 µ3

�

w l Eo

σ σ

µ2 µ3

�

w l Eo

σ σ

µ2 µ3

5.3 Epenthesis As with the OT account, let us assume that properties of syllabification deter-mine the location of the epenthetic vowel (Itô 1986, 1989). At issue is the qual-ity of the epenthetic vowel in the unconditioned environments. In a fully speci-fied account, the quality of the epenthetic vowel would either be completely ar-bitrary or else determined by some theory of markedness that would need to be explicitly laid out. The underspecified account constitutes one version of such a theory of markedness (Kiparsky 1982, 1985, Pulleyblank 1986, Archangeli 1988, Calabrese 1995, Steriade 1995, etc.).

The central claim of the underspecification approach is that markedness renders a class of redundancy rules cost-free and that fully underspecified vow-els are the cumulative result of underspecification for each individual feature.

Yoruba vowel patterns 17

Assume, to be concrete, that the class of cost-free redundancy rules includes the following:

(29) Redundancy rules a. [ ] � [+High] c. [ ] � [–Back] b. [ ] � [–Low] d. [ ] � [+Atr] Given this set of redundancy rules, the parenthesised specifications in (30) would be excluded from underlying representations and supplied by the applica-tion of the redundancy rules.17

(30) Underspecified vowel specifications i e e¢ a o¢ o u

[High] (+) – – – – – (+) [Low] (–) (–) (–) + (–) (–) (–) [Back] (–) (–) (–) + + + + [Atr] (+) (+) – – – (+) (+)

The result of this proposal is that an epenthetic vowel receives the specifi-cations appropriate for [i] cost-free. Syllable structure forces the inclusion of a prosodic vowel position; the redundancy rules supply the appropriate quality.

5.4 Assessment In comparing rule-based and constraint-based accounts of the Yoruba patterns, it is important to distinguish between issues involving ‘rules’ vs. ‘constraints’ and issues involving ‘underspecification’ vs. ‘sonority-based markedness’. I discuss issues involving rules vs. constraints in this section and examine issues involv-ing underspecification vs. sonority-based markedness in §9.

A basic problem for a rule-based approach to hiatus resolution involves the cooccurrence both in Yoruba and generally of multiple ‘rules’ conspiring to eliminate hiatus. A property that clearly emerges from cross-linguistic studies such as Rosenthall (1994) and Casali (1996, 1997) is that languages typically either tolerate hiatus generally or eliminate it generally. Such typical patterns are the result of a factorial typology involving the three constraints deriving the Yoruba pattern.

17 Only context-free redundancy rules are illustrated here. It would also be possible to reduce

the specifications for [a] to [+low] by the inclusion of context-sensitive redundancy rules: [+Low] � [–High], [+Low] � [+Back], [+Low] � [–Atr].

18 Pulleyblank

(31) Factorial typology Ranking Hiatus Pattern of vowel loss a. MAX >> ANCHORL >> NOHIATUS tolerated b. MAX >> NOHIATUS >> ANCHORL tolerated c. ANCHORL >> MAX >> NOHIATUS tolerated d. ANCHORL >> NOHIATUS >> MAX eliminated V1 deletion e. NOHIATUS >> ANCHORL >> MAX eliminated V1 deletion f. NOHIATUS >> MAX >> ANCHORL eliminated quality-sensitive deletion

Where NOHIATUS outranks MAX, hiatus is eliminated; where MAX outranks NOHIATUS, hiatus is tolerated. When hiatus is eliminated, the general pattern where V1 deletes results when ANCHORL outranks MAX, while the quality-sensitive pattern observed in Yoruba results when MAX outranks ANCHORL.

Within a rule-based approach, the same generality of either hiatus avoid-ance or tolerance does not follow. Since conditions may and in some cases must be imposed on a rule applying in a hiatus context, it is straightforward to postu-late a system where a conditioned rule applies in some hiatus contexts and where the grammar posits no additional rule to apply in those hiatus contexts not covered by the conditioned rule. According to any simplicity metric assigning a cost to a rule (e.g. Chomsky & Halle 1968), a grammar involving two rules of hiatus resolution is more costly than a grammar involving a single rule. The pre-diction is therefore made that if grammars exist that require a special rule of hia-tus resolution in addition to a general rule, then grammars should also exist with the special rule only – a language where hiatus will be eliminated in some cases and tolerated in others. The apparent rarity of such grammars is a problem for a rule-based theory. The central problem is that hiatus resolution plays no formal unifying function in a rule-based approach, at best constituting some sort of meta-constraint on rules. A possible way of formally codifying the role of hiatus prohibition would be to impose it as a constraint, with the rules as ‘repair strate-gies’ (Paradis 1988, etc.) but the crucial and unifying property of such an analy-sis would be the constraints, not the repairs.

I should be careful not to give the impression that the constraint-based theory is without its own problems. For example, if one attributes frequency of occurrence cross-linguistically to the number of grammars deriving a particular surface pattern, then the factorial typology in (31) predicts that V1 deletion should be more frequent than quality-sensitive deletion. From the discussion in Casali (1997), this prediction appears correct, but too weak. Not only does qual-ity-sensitive deletion appear to be less frequent, but it appears to be massively less frequent. I speculate that this cross-linguistic skewing results from certain constraints being intrinsically stronger than others. For the case in question, I speculate that the processing factors that cause left-edge anchoring to be highly ranked are strong factors cross-linguistically.

Yoruba vowel patterns 19

In the following sections, I consider two additional configurations in Yoruba where vowel hiatus would result from the juxtaposition of two vowels. Both the OT analysis presented here and a rule-based analysis make predictions about the expected outcome in such cases, and as we will see, it is only the OT analysis that makes the correct predictions.

6 Consonant deletion and progressive assimilation Whereas phrase-level V V sequences give rise to regressive assimilation, as just seen, V V sequences derived by the deletion of an intervocalic consonant give rise to progressive assimilation. Consider the data in (32) (Oyelaran 1971).

(32) Progressive Root Spread a. agogo [agogo] aago [aago] ‘bell’ otu!tu~ [otutu] oo!tu~ [ootu] ‘chill’ e~su!su! [esusu] e~e!su! [eesu] ‘traditional form of banking’ b. egungun [egu)gu)] eegun [eegu)] ‘bone’ ogu~ngu~n [ogu)gu)] oo~gu~n [oogu)] ‘medicament’ o~¢ka!nka!n [O~ka)ka)] o~¢o!¢ka!n [O~O~ka)] ‘open view’

The examples in (32a) illustrate consonant deletion between two oral vowels, while the examples in (32b) illustrate consonant deletion between an oral and a nasalised vowel. Consonant deletion itself is optional, depending on factors such as dialect and speech rate.18 Whenever consonant deletion takes place, however, then progressive assimilation is obligatory. For example, [agogo] alternates with [aago] (*[aogo]/*[oogo]) and [O~ka)ka)] alternates with [O~O~ka)] (*[O~a)ka)]/*[a~a~ka)]/ *[a~a)Ÿka)]/ *[a)Ÿa)Ÿka)]).

In the account proposed here, the analysis already presented produces the correct results in consonant-deletion cases. Consider (33).

(33) Consonant deletion NOHIATUS *C1 MAX ANCHORL a. [agogo] *! /agogo/ b. [aogo] *!

c. � [aago] nonhi d. [oogo] nonhi *!

18 The issue of how to account for the consonant deletion itself is orthogonal to the issue of

vowel assimilation and will not be addressed here. One possibility would be to assume a constraint prohibiting a sequence of identical consonants, represented here as “*C1” since it is the first of the identical consonants that deletes. This analysis could be formalised ac-cording to the Generalised OCP of Suzuki (1998). The constraint in question needs to be ranked above faithfulness to consonants (MAXC).

20 Pulleyblank

The candidate retaining both consonants (33a) is ruled out by *C1. The prohibi-tion on nonidentical vowel sequences (NOHIATUS) rules out *aogo (33b). Since both aago (33c) and *oogo (33d) violate MAX in a comparable fashion (both de-lete nonhigh vowels), the choice between the two defaults to a lower ranked constraint, specifically ANCHORL.

Of interest is that ANCHORL produces a surface effect here that is exactly the opposite of that seen previously. Recall that left-edge anchoring is highly ranked in Yoruba. In the phrasal cases, this means that ANCHOR protects V2 in a V1][V2 sequence; in the consonant deletion cases, however, reference to a left-edge means that ANCHOR protects V1 in a [V1V2 sequence. Exactly the same con-straint, therefore, is responsible for the regressive assimilation phrasally and the progressive assimilation word-internally.

In contrast, such data are problematic for a rule-based account. All else being equal, one would expect a sequence of vowels resulting from consonant-deletion to behave in exactly the same way as a sequence of vowels resulting from morpheme concatenation. Just as in (1), this would lead one to expect pro-gressive assimilation in some cases and regressive assimilation in others, an ex-pectation that is not borne out by the facts. Let us consider briefly both fully specified and underspecified rule-based analyses.

In a fully specified analysis, Progressive Spread (24a) would correctly be applicable in cases where the second vowel in the relevant VCV sequence is high. Thus cases like oo!tu~ ‘chill’ (<otu!tu~) and eegun ‘bone’ (<egungun) pose no problems. Cases like aago ‘bell’ (<agogo) and o~¢o!¢ka!n ‘open view’ (<o~¢ka!nka!n), however, are problematic. Progressive spread would not be applicable since the second vowel in the relevant sequence is nonhigh, hence regressive assimilation, not progressive assimilation, would be expected.

In the underspecified analysis, the specifics would be different, but the re-sults would be at least as bad. Regressive Spread (25a) would apply first, and its structural description would be met by all of the forms in (32). As a result, re-gressive assimilation would be incorrectly predicted for all forms in (32).

These problems are not hard to solve. In both fully specified and under-specified accounts, a special rule of progressive assimilation could be posited for these cases, distinct from the independently established rule of Progressive Spread (24a). This is clearly an ad hoc solution to this class of cases since a new rule would be postulated specifically for this class of cases, differing only in not including the [+high] condition on the target that is seen phrasally. An alterna-tive available to the underspecified account would be to order identical conso-nant deletion after Regressive Spread (25a) but before Progressive Spread (25b).

The difference between the constraint-based account and the rule-based accounts, therefore, is not that one account is able to derive the observed facts while the others are not – the point is more subtle. In different contexts, vowel hiatus arises. In the constraint-based account, different results are predicted for

Yoruba vowel patterns 21

different hiatus contexts because of the basic nature of the hiatus-resolution con-straints. In the rule-based accounts, different hiatus contexts either require the postulation of different rules, or the imposition of special orderings that are re-quired in one case but not another.

7 Distributive reduplication Another configuration that requires hiatus resolution is distributive reduplication (Akinlabi 1984, Fo ¢larin 1987, Pulleyblank 1988a, in press, O¢la 1995).

(16) Distributive Reduplication a. os¢u~ [oSu~] os¢oos¢u~ [oSooSu~] ‘month; every month’ ale!¢ [alE!] alaale!¢ [alaalE!] ‘night; every night’ or¸ !̨ [or¸ !̨] oroor¸˛! [oroor¸˛!] ‘head; every head’ b. oju!mo!¢ [oÔu!mO)⁄] ojooju!mo!¢ [oÔooÔu!mO)⁄] ‘day; every day’ o¢du!n [Odu⁄)] o¢do¢o¢du!n [OdOOdu⁄)] ‘year; every year’ c. ¸ ~̨ta~do!gu!n [¸ ~̨ta~do!gu⁄)] ¸ ~̨t¸ ~̨¸ ~̨ta~do!gu!n [¸ ~̨t¸ ~̨¸ ~̨ta~do!gu⁄)] ‘15th day; every 15th

day’ ¸ ~̨gbe!¢ [¸ ~̨gbE!] ¸ ~̨gb¸ ~̨¸ ~̨gbe!¢ [¸ ~̨gb¸ ~̨¸ ~̨gbE!] ‘forest; every forest’

Prosodically, distributive reduplication involves the affixation of a foot to a nominal base (O ¢la 1995). Examples like ojooju!mo!¢ ‘every day’ and ¸ ~̨t¸ ~̨¸ ~̨ta~do!gu!n ‘every fifteenth day’ motivate this delimitation to a foot since reduplication is of two moras, not of the complete base.19 Tonally, the distributive bears the same tone as the first mora of the base. Hence it is mid if the first mora of the base is mid, low if the first mora of the base is low. For discussion of both prosodic and tonal aspects of the distributive, see Pulleyblank (in press).

The aspect of the distributive that is important here is vowel hiatus. If the copying of distributive reduplication was vocalically ‘perfect’, then we would expect outputs like *os¢uos¢u~, *orior¸ !̨ and * ~̧gbE~¸ ~̨gbE!. Such outputs would be ill-formed, however, because they involve illicit vowel sequences. To resolve the problem, vowel hiatus needs to be eliminated.

Consider the required vowel hiatus resolution from two perspectives, the perspective of a rule-based analysis and that of Optimality Theory. From the perspective of a rule-based theory, the expectation would be that hiatus be re-solved by the independently motivated rule set. It turns out, however, that the otherwise motivated rule set is incapable of deriving the attested results. The straightforward observation about reduplicative hiatus resolution is that vowel assimilation is systematically regressive. Straight off, this means that the special

19 Whether the formal analysis of distributive reduplication is defined in terms of a prosodic

target (O¢la 1995), or in terms of generalised templates (see Urbanczyk 1996, McCarthy & Prince 1999 and references therein) is of no importance for the point being made here.

22 Pulleyblank

rule of progressive assimilation seen in the consonant-deletion forms must not apply in reduplicative forms. Let us in fairly blatant style assume therefore that the special progressive assimilation is somehow restricted so as to be applicable after consonant deletion but inapplicable with reduplication. As such, it can be disregarded here. The explanatory success or failure of the rule-based analysis would therefore depend on whether either combination of full specification or underspecification with progressive and regressive spread can derive the correct reduplicative forms.

With fully specified vowels (24), Progressive Spread would apply first, causing progressive assimilation in any case with a high stem-initial vowel:

(34) Assuming full specification /Red + oSu~/ /Red + or¸ !̨/ /Red + ¸ ~̨gbE!/ Reduplication oSu oSu~ ori or¸ !̨ ¸ ~̨gbE~ ¸ ~̨gbE! Progressive Spread (24a) n/a n/a ¸ ~̨gbE~ E~gbE! Regressive Spread (24b) oSo oSu~ oro or¸˛! n/a Output [oSooSu~] [oroor¸˛!] *[¸ ~̨gbE~E~gbE!]

While Regressive Spread would correctly apply in cases like oSooSu~ and oroor¸˛!, Progressive Spread would incorrectly derive *¸ ~̨gbE~E~gbE! when the initial vowel of the base is high.

With underspecified inputs, Regressive Spread would apply first, but would be inapplicable if the initial base vowel is high:

(35) Assuming underspecification /Red + oSu~/ /Red + or¸ !̨/ /Red + ¸ ~̨gbE!/ Reduplication oSu oSu~ ori or¸ !̨ ¸ ~̨gbE~ ¸ ~̨gbE! Regressive Spread (25b) oSo oSu~ oro or¸˛! n/a Progressive Spread (25a) n/a n/a ¸ ~̨gbE~ E~gbE! Output [oSooSu~] [oroor¸˛!] *[¸ ~̨gbE~E~gbE!]

The results would be identical to the fully specified account, and equally bad.

Contrast the expectations of the rule-based account with the expectations of the OT account developed here. Reduplication per se would be derived by constraints that are orthogonal to the question of hiatus resolution. One possible analysis would be to invoke base-reduplicant correspondence with delimitation by a prosodically defined foot template (O ¢la 1995); a comparable analysis would be possible invoking a morphologically defined definition of the distribu-tive along the lines of generalised template theory; a third possibility is to in-voke constraints that make no direct reference to a ‘reduplicant’, but derive re-duplication by the low-ranking of INTEGRITY (Pulleyblank in press). For present purposes, nothing crucial depends on the choice made between these analyses.

Yoruba vowel patterns 23

The crucial point to note is that the three analyses share one core property. The input to a reduplicated form contains a phonologically specified base with a minimally specified distributive prefix. This prefix might contain only morpho-logical specifications (the ‘generalised template’ analysis); if it contains phono-logical specifications, then this would only be the specification ‘Foot’ or ‘Mini-mal Word’. Abstracting away from the issue of hiatus resolution, consider the correspondence relations of a ‘perfect’ case of reduplication.

(36) Correspondence relations

[ i gb E ] [ i gb E ]

RED + [ i gb E ]

Input-Output correspondence

Reduplicant-Base correspondence Because the reduplicant has no input content, there is no input-output corre-spondence with the reduplicant. That is, segments of the reduplicant are in cor-respondence with segments of the base, but not directly with segments of the in-put. The result of this pattern of correspondence is that input-output faithfulness applies only to the relation between the input and the base, but not between the input and the reduplicant. This has interesting consequences for hiatus resolu-tion. Consider the tableau in (37).

(37) Vowel hiatus in reduplication NOHIATUS MAX ANCHORL a. [¸ ~̨gbE~¸ ~̨gbE!] *! /Red + ¸ ~̨gbE!/ b. [¸ ~̨gbE~E~gbE!] HiFr! * c. � [¸ ~̨gb¸ ~̨¸ ~̨gbE!]

NOHIATUS rules out a candidate with perfect copying (37a) since the result of perfection would be an illicit sequence of vowels. MAX exerts pressure to retain properties of the base only, since the segments of the reduplicant are not in an input-output correspondence relation with input segments. As a result, MAX is violated if hiatus is resolved via ‘progressive assimilation’ (37b) but satisfied in a candidate exhibiting ‘regressive assimilation’ (37c). ANCHORL, though not di-rectly relevant because of its ranking below MAX, has an effect that is consistent with MAX in this type of case, violated if the first segment of the base is lost.

These cases provide supporting evidence for the proposal that sonority distinctions should be directly encoded as part of faithfulness rather than via a constraint such as HNUC. Compare the successful account of (37) with the alter-native account where HNUC is employed rather than sonority-sensitive MAX.

24 Pulleyblank

(38) Sonority reflected in faithfulness, not HNuc NOHIATUS HNUC ANCHORL a. [¸ ~̨gbE~¸ ~̨gbE!] *! …Nonhi HiFr… /Red + ¸ ~̨gbE!/ b. � [¸ ~̨gbE~E~gbE!] …Nonhi… * c. [¸ ~̨gb¸ ~̨¸ ~̨gbE!] …HiFr!…

To obtain the general effects observed in assimilation contexts, HNUC must out-rank ANCHORL (see (16)) – but this ranking would incorrectly predict *¸ ~̨gbE~E~gbE! instead of ¸ ~̨gb¸ ~̨¸ ~̨gbE!. The crucial difference between HNUC and so-nority-sensitive MAX is that HNUC is blind to the source of the vocalic nucleus while MAX specifically governs an input-output relation.

The results seen with consonant deletion and reduplication make the over-all constraint-based analysis increasingly compelling. In a variety of contexts, we see that the constraints NOHIATUS, MAX and ANCHORL correctly determine the observed surface patterns. First, when hiatus would result from the juxtapo-sition of two morphemes, the result is variable, with assimilation or deletion de-termined by prosodic factors and regressive vs. progressive assimilation deter-mined by the interplay of sonority-sensitive MAX and sonority-blind ANCHORL. Second, when hiatus would result from consonant deletion, the situation changes because ANCHORL constitutes pressure to preserve the first vowel in the VV rather than the second vowel as in a V##V sequence. Third, when hiatus arises as a result of reduplication, the situation is different again because input-output MAX does not govern the reduplicant. Three very different patterns are predicted by a single ranking of the same constraints.

With rules, the situation is entirely different. Rules can be created that will describe the effects in all contexts: a pair of rules is established for the juxtaposi-tion case; a new rule is added for the consonant-deletion case or an order is im-posed that was not independently required; a new rule is added for the reduplica-tion case. The rule-based approach offers no explanation for any of the hiatus-resolving behaviour. Instead of the three or four rules that appear to be required, there could just as easily have been none, or one, or two, or five. The rules are totally ad hoc in that each rule or pair of rules is engineered for a particular con-figuration, and shows no general applicability.

In the remaining sections of the paper, I shift the emphasis away from is-sues of rules vs. constraints to issues specifically concerning the encoding of asymmetries based on vowel quality. First, a case will be considered that di-rectly involves the gradient effect whereby nonhigh vowels are more sonorous than high vowels, and high back vowels are more sonorous than high front vow-els. I will then consider general issues concerning the underspecification option, addressing cases where patterns appear to require direct reference to the prop-erty [+high].

Yoruba vowel patterns 25

8 Dialects with u-initial words As noted in §3, Standard Yoruba does not allow nouns to begin with [u-]. This unfortunately makes it impossible to test analytic predictions regarding the be-haviour of …V][u… sequences arising across word boundaries. In certain dia-lects, however, the prohibition on u-initial words does not hold. I consider such cases in this section, examining the predictions made by derivational analyses with and without underspecification, and by the constraint-based analysis pre-sented here. Specifically, I examine the dialect of Ekiti (Adeniyi 1988, Omisore 1989), making the assumption that the only relevant distinction between Ekiti and Standard Yoruba is whether u-initial forms are allowed (Ekiti) or prohibited (Standard Yoruba). It will be shown that by making this assumption, the con-straint-based analysis makes exactly the correct predictions for u-initial forms in Ekiti, while rule-based analyses make incorrect predictions. As with the patterns of hiatus-induced assimilation, it is not the case that derivational analyses cannot in one way or another account for the data observed in u-initial dialects. The point is that the behaviour of u-initial forms is unexpected in a rule-based ac-count, and must be accounted for by the postulation of special ad hoc rules.

For vowel sequences not involving u-initial nouns, rule-based and con-straint-based analyses make identical predictions. Since the analyses were all designed to produce the patterns described in §2, this identity in predictions is not surprising. Here is a brief recap of the relevant patterns. Consider cases where the second vowel in a …V1][V2… is nonhigh. In both fully specified and underspecified derivational analyses, Regressive Spread will apply in such cases, deriving a surface result …V2][V2…; in the constraint-based analysis, an-choring will enforce the retention of V2 whether V1 is equally sonorous or less sonorous than V2. Where V2 is the high front vowel [i], the three analyses again make comparable predictions. Progressive Spread will apply in both derivational accounts deriving …V1][V1…; in the optimality theoretic account, MAXNONHI and MAXHIBK will similarly force the retention of V1, even at the cost of violat-ing ANCHORL.

These patterns constitute the control case. If the grammar of Ekiti is fully comparable to Standard Yoruba in its treatment of …V][V… sequences, then these sequences should behave in the same way in the two dialects—and this is indeed the case. The relevant patterns are summarised in the following sche-matic table, where E = any nonhigh vowel, I = any high front vowel, and U = any high back vowel.20

20 The u-initial dialects under consideration also exhibit harmonic variation in the high vow-

els, unlike Standard Yoruba. As a result, there are two high front vowels [i, I] and two high back vowels [u, U]. Advanced and retracted high vowels behave the same way with respect to vowel assimilation.

26 Pulleyblank

(39) Summary where nouns are not u-initial E1][E2 E][I I][E U][E U][I Fully specified: E2][E2 E][E E][E E][E U][U Underspecification: E2][E2 E][E E][E E][E U][U Optimality Theory: E2][E2 E][E E][E E][E U][U Ekiti data: E2][E2 E][E E][E E][E U][U

Data exemplifying the Ekiti patterns are given in (40).

(40) Ekiti patterns that are comparable to Standard Yoruba a. V2 retained: the general pattern

E1][E2 [ule! o~dZo!] [ulo!o~dZo!] ‘house of Ojo’ [a~ba! EgbE!] [a~bE!EgbE!] ‘father of club/patron’ [OdZa~ Oba] [OdZO~Oba] ‘market of king’

I][E [om )̧ Era)] [omE)E)ra)] ‘water of meat’ U][E [ ~̧lu! O~wO~] [ ~̧lO!O~wO~] ‘a town’21

b. V1 retained: V1 = high back; V2 = high front E][I [eo! igi] [eo!ogi] ‘money for wood’ U][I [ErU) ~̧gb )̧⁄] [ErU)U)Ÿgb )̧⁄] ‘mouth of snail’22

As illustrated, the basic pattern in Ekiti is comparable to that of Standard

Yoruba, with the high front vowel behaving in an asymmetric pattern. Of inter-est are the cases where the second noun begins with [u-]. These cases turn out to be particularly interesting because the three analyses under discussion each make different predictions in their regard. There are two configurations of inter-est. In the first, a noun ending in a nonhigh vowel is followed by a noun that is u-initial; in the second, a noun ending in a high front vowel is followed by a noun that is u-initial. The predictions for such cases are schematised in (41).

(41) Predictions where the second noun is u-initial E][U I][U Rule-based – fully specified representations: E][E I][I Rule-based – underspecified representations: U][U U][U Constraint-based – sonority dependent faithfulness: E][E U][U Ekiti data: E][E U][U

21 This form presumably undergoes glide deletion: [¸~lu! O~O~]/[ ~̧lO! O~O~]. See Omisore (1989). 22 The effect of tongue root harmony was not indicated in the form for ‘mouth’ ([ErU)]) at the

place where ‘mouth of snail’ was presented in Omisore (1989), although the fact that the final vowel of [ErU)] is retracted is clearly indicated in Omisore’s discussion of harmony. Assuming this was a typographical error, I have represented ‘mouth of snail’ accordingly.

Yoruba vowel patterns 27

In a fully specified account, Progressive Spread (24a) is the first rule to

apply and it targets high vowels. In any configuration where a high back vowel follows another vowel, therefore, the initial [u-] should undergo left-to-right as-similation (E][E & I][I). In contrast, the underspecified account applies Regres-sive Spread (25a) first. Since any vowel with specifications triggers Regressive Spread, the initial [u-] should trigger the rule, deriving a surface right-to-left pat-tern, the opposite result to the fully specified account (U][U in both cases). Fi-nally, the proposed optimality theoretic account should produce a result compa-rable to the fully specified derivation approach in one case and to the under-specified approach in the other. To see this, consider each case. With an input /…E][U…/, MAX militates in favour of retention (and therefore spreading) of the word-final nonhigh vowel since a nonhigh vowel is higher on the sonority scale than a high back vowel; ANCHORL militates in favour of retention (and therefore spreading) of the word-initial vowel, that is, the second vowel. Since MAX outranks ANCHORL, progressive assimilation is predicted: E][E. With an input /…I][U…/, exactly the opposite pattern results. Since a high back vowel is more sonorous than a high front vowel, MAX favours retention of the high back vowel; ANCHORL provides additional pressure for the same result. The predicted result is therefore regressive assimilation: U][U.

As can be seen from the final row of (41), it is the pattern predicted by the optimality theoretic analysis that is actually attested. Illustrative data from Ekiti (Adeniyi 1988, Omisore 1989) are presented in (42).

(42) Ekiti patterns with high back vowels a. V2 retained: the general pattern

E][U [ule! USE!] [ule!eSE!] ‘place of work’ b. V1 retained: V1 = high back; V2 = high front

I][U [et !̧ ule!] [etu!ule!] ‘near house’

Sample tableaux are presented in (43).

(43) Phrasal vowel sequences in Ekiti NOHIATUS MAX ANCHORL a. [ule USE] *! (i) /ule USE/ b.� [ule eSE] HiBk * c. [ulU USE] Nonhi! d. [eo igi] *! (ii) /eo igi/ e.� [eo ogi] HiFr * f. [ei igi] Nonhi!

28 Pulleyblank

NOHIATUS MAX ANCHORL g. [eti ule] *! (iii) /eti ule/ h. [eti ile] HiBk! * i.� [etu ule] HiFr j. [ErU) igb )̧] *! (iv) /ErU) igb )̧/ k.� [ErU) U)gb )̧] HiFr * l. [Eri igb )̧] HiBk!

While it is clearly possible to engineer accounts for Ekiti within rule-

based theories, the point of interest here is that exactly the analysis proposed for Standard Yoruba within Optimality Theory accounts for Ekiti as well. The sole difference of consequence between the two varieties is whether u-initial nouns are permitted (Ekiti) or not (Standard Yoruba).23 In particular, sequences like [Eru~ igi]/[Eru~ugi] ‘bundle of wood’ in Standard Yoruba demonstrate crucially that faithfulness to the more sonorous [u] takes precedence over faithfulness to the less sonorous [i] (see the tableau in (12)). The relevant Ekiti sequence where an i-final noun precedes an u-initial noun provides the mirror effect, e.g. [et !̧ ule!]/ [etu!ule!] ‘near house’ – the same sonority-based faithfulness constraint results in the retention of [u] in V2 position.

9 Underspecification The basic motivation for the underspecified representations proposed for Yoruba in Pulleyblank (1988a) was that a cluster of rules treated high vowels in general and the vowel [i] in particular as special. If rules simply repeatedly included the appropriate featural restrictions in their structural descriptions, nothing was ex-plained. Moreover, the underspecified representations attempted to explain par-ticular changes. For example, the presence of a specified value correlated with featural stability, while its absence correlated with featural malleability.

Invoking structural underspecification to account for such featural asym-metries encounters both general and Yoruba-specific problems. At a general level, there are various theoretical problems with the theory of underspecifica-tion; for discussion, see Mohanan (1991), McCarthy & Taub (1992), Steriade (1995), Frisch, Pierrehumbert & Broe (in press), etc. Compounding its general problems, underspecification is particularly problematic within Optimality The-ory since a fundamental tenet of OT is that constraints are imposed only on out-

23 There is another relevant difference. In Ekiti, assimilation eliminates hiatus across feet as

in Standard Yoruba. This can be seen in an example like [ule! o~dZo!]/[ulo!o~dZo!] ‘house of Ojo’ where a sequence of nonhigh vowels is eliminated. In contrast with Standard Yoruba, Ekiti tolerates such sequences in word- and foot-internal cases like [eo!] ‘money’.

Yoruba vowel patterns 29

put representations.24 But in order for [i] to be special in all forms, it is essential that all instances of [i] be special. So if the special property of [i] is input under-specification, then all instances of [i] must be appropriately underspecified.

There are three plausible approaches to such underspecification. One would be to impose underspecification as a condition on inputs – incompatible with the general output orientation of OT just mentioned. Another would be to adopt monovalent features, where the features were defined so as to make [i] completely unspecified for place:

(44) Putative monovalency for Yoruba i e e¢ a o¢ o u

[Nonhi] Nonhi Nonhi Nonhi Nonhi [Low] Low [Back] Back Back Back [Rtr] Rtr Rtr Such an approach to feature specification is both unlikely and inadequate. It is unlikely because actual proposals for monovalent theories of features have ar-gued for [High], not [Nonhigh] (e.g. Steriade 1995). With the vowels [i, u] specified as [High], the asymmetries observed in Yoruba could not be derived.

A third possible approach to achieving underspecification would be to adopt the proposals for licensing in Itô, Mester & Padgett (1995). Their proposal centres on defining relations to redundancy. If a feature F is redundant with re-spect to some feature G, then F is not licensed by G. For example, since [voice] is redundant for a [nasal] consonant, a [nasal] consonant does not license [voice]. Whatever the overall status of the licensing proposal, it would be inade-quate for Yoruba since the feature value [+high] is not redundant with respect to any other feature (Mohanan 1991). This point is independent of any particular feature set, hence can be made with reference to binary features (see (30)) just as it could be made with a feature set including a monovalent [High]. Since being [+high] cannot be predicted on the basis of any values of [±low], [±back] or [±atr], the value [+high] would be licensed, hence specifiable in the optimal vowel representation.

Setting aside the theoretical problems with an underspecified account, the most significant problem for Yoruba is the one already referred to in the intro-duction. Whatever its details, an underspecified analysis such as in (44) provides no way of directly referring either to the class of high vowels or to the sub-class of high front vowels. This is not a problem when ‘reference’ to high vowels can be by-passed. For example, the special property of reassociation observed with

24 Faithfulness constraints consitute the one exception to this as they impose restrictions on

the mapping between input and output.

30 Pulleyblank

the high front vowel under deletion (28) falls out from its being devoid of speci-fications. Problematical, however, are processes that require direct reference to the property of being high. Such cases are discussed in the following section.

10 Reference to [+high] Patterns apparently requiring reference to [+high] (Clements & S ¢onaiya 1990, Akinlabi 1993) are problematical for the underspecified account of Yoruba vowel asymmetries proposed in Pulleyblank (1988a) since the underspecifica-tion hypothesis provides no [+high] value to be referenced. Since the inclusion of [+high] values in representations is fully compatible with a constraint-based analysis invoking sonority, the existence of patterns that crucially refer to [+high] is fully consistent with the proposal made here. As such, I will discuss only briefly some of the cases argued in the literature to apply to the feature value [+high].

Three sub-types can be distinguished, based on the relevance of the case for the proposals made here. First, some cases can be formulated with reference to [+high] that could equally well be formulated with reference to [–high]. For example, in Standard Yoruba the feature for tongue root retraction ([–atr]) may not be assigned to high vowels, a prohibition that could be expressed as *[–atr, +high]. As shown in Archangeli & Pulleyblank (1989, 1994), however, this pro-hibition can equally well be expressed by an implication “If [–atr] then [–high].” Whether there is some reason to prefer one form or other of the prohibition would therefore crucially depend on whether evidence could be presented re-quiring representations underspecified for either [+high] or [–high]. With regard to the patterns of vowel harmony in Yoruba where the prohibition on high re-tracted vowels is relevant, it is unlikely that any evidence can be found (see Pul-leyblank & Turkel 1996). Note that since the two conditions *[–atr, +high] and [–atr] � [–high] are logically equivalent for fully specified representations, there can be no reason to prefer one over another unless independent evidence can be found forcing underspecified representations (cf. de Lacy 2002). Hence the implicational relation between vowel height and vowel retraction provides no argument either for or against reference to either [+high] or [–high].

A second type of case involves reference to [+high] in a manner that is apparently unrelated to the proposals made here. For example, Clements & S¢onaiya (1990) discuss a constraint that they express informally as “*[{a,O} C {i,u}]N”. This constraint prohibits oral high vowels from appearing after a re-tracted back vowel in nouns. To refer to the class {i,u}, it is necessary to refer to the feature value [+high] – a reference that is inconsistent with an underspecified analysis (as they point out) but fully compatible with the analysis proposed here. Since the constraint bears no obvious relation to sonority, it provides no evi-dence in favour of the specific proposal for deriving the properties of high vow-els from sonority-conditioned faithfulness. With our current understanding, such

Yoruba vowel patterns 31

a constraint is unexplained, though fully consistent with the representations for vowels motivated here.

The third type involves processes that require reference to [+high] – and therefore are incompatible with underspecification – but that are amenable to the sonority-based proposal made here. Two possible cases involve nasality and r-deletion. Because the validity of the constraint-based analysis of high vowels presented here is not directly at issue, I will not discuss these cases in any detail but will make some schematic comments regarding one of the processes, namely, r-deletion.25

The topic of r-deletion, discussed in detail in Akinlabi (1993), is large and complex, exhibiting significant amounts of interdialectal variation, and involv-ing the interplay of segmental and prosodic factors. The basic pattern described by Akinlabi is one where [r] deletes between two identical vowels (e.g. [we~re~pe~] ~ [we~e~pe~] ‘nettle’, [e~¢re~¢ke¢] ~ [e~¢e~¢ke¢] ‘cheek’) and adjacent to a high vowel (e.g. [o~r¸˛~s¢a~] ~ [o~o~s¢a~] ‘god’, [o¢lo¢!run] ~ [o¢lo¢!un] ‘God’ vs. [e¢ro¢~fo¢~], *[e¢o¢~fo¢~]/*[e¢e¢~fo¢~]/*[o¢o¢~fo¢~] ‘nettle’). While it would be possible to adopt con-straint-based analogs of the rules proposed by Akinlabi – that is, constraints prohibiting [r] between identical vowels and adjacent to a [+high] vowel – Ak-inlabi’s treatment of the observed alternations suggests an alternative. If a high-ranking constraint against [r] is posited, then conditions governing the avoidance of hiatus would largely determine when deletion is possible or impossible.

The crucial cases to consider are those sequences including a high vowel.26 Consider four possible output candidates for an input sequence such as in [o~r¸˛~s¢a~] ‘god’. If the [r] of the input is retained in the output, [o~r¸ ~̨s¢a~], the high ranking constraint against [r] would be violated. If the input [r] is deleted with no further changes [o~¸ ~̨s¢a~], then NOHIATUS is violated. Outputs satisfying both the constraint against [r] and NOHIATUS can be achieved via assimilation, either progressive [o~o~s¢a~] or regressive [¸ ~̨¸ ~̨s¢a~]. The progressive case violates MAX since it loses the features of [i] but the regressive case violates MAX more seriously as it loses the features for the more sonorous [o]; in addition, the regressive case violates ANCHORL. Hence while none of the candidates are perfect, the optimal

25 The patterns of nasal assimilation and stability involve both consonants and vowels and

are directly relevant to the issues of vocalic asymmetries, as made clear in both Pulley-blank (1988a) and Clements & S ¢onaiya (1990). Because of its relevance for fixed segmen-tism in reduplication (Alderete et al 1999), nasality is given a detailed treatment in Pulley-blank (in press), an examination of several types of Yoruba reduplication. It is argued in that paper that nasal patterns are fully compatible with the proposals for vocalic asymme-tries presented here.

26 In the case where [r] is between identical vowels, Akinlabi argues for a representation where one set of vowel features is multiply-linked over an unspecified [r]. If correct, this would mean that the loss of [r] would not result in a violation of NOHIATUS and r-deletion would correctly be predicted to occur.

32 Pulleyblank

output is the one involving progressive assimilation: [o~o~s¢a~]. If an analysis along these lines proves adequate, then the basic pattern of r-deletion and assimilation can be achieved by positing a context-free prohibition on the presence of [r] in conjunction with independently motivated constraints.27

11 Conclusion Structural properties of vowel representation seem largely orthogonal to the asymmetries observed in the Yoruba vowel system. Of crucial importance is a harmonic scale where the inertia of more sonorous vowels prevails over that of less sonorous vowels. The grammaticisation of this sonority-based pattern inter-acts with constraints governing various specific patterns of Yoruba phonology to produce interlocking patterns of vocalic asymmetries.

Rule-based accounts of Yoruba vowel patterns succeed in describing the range of patterns, but fail to explain them. Whether direct reference to feature values such as [+high] and [–high] is allowed, or whether underspecification for [±high] is assumed, rule-based accounts of Yoruba require a plethora of rules, each one tailored to a particular construction and building in the particular be-haviour of vowels with respect to their height. Note in particular that the under-specified approach of Pulleyblank (1988a) predicts some of the patterns of vowel behaviour, but predicts the opposite of the observed facts in other cases – obviously a serious problem for such an account. Were such an analysis to be reframed in terms of monovalent features, the problem would only be aggra-vated due to the structural inflexibility of such features.

In marked contrast, the optimality theoretic account proposed here suc-ceeds by postulating a basic constraint set governing faithfulness to vocalic specifications, where the proposed set is based on considerations of sonority. This basic vocalic set then interacts directly with the constraints that govern other aspects of Yoruba phonology, for example, the constraints on hiatus, redu-plication, the consonant inventory, and so on. The core of the proposal is the core set of vocalic constraints – those governing vocalic faithfulness.

The proposed account examines a significant portion of the phonology of Yoruba involving vowels, but is not, however, exhaustive. For example, matters of vowel epenthesis were mentioned only briefly and vowel harmony has been left unexamined.28 While it would be desirable for a comprehensive treatment of vocalic phenomena to include a treatment of these phenomena, their analysis

27 Not all examples behave like [o~r¸ ~̨s¢a~]/[o~o~s¢a~]. For example, when [r] is deleted after a high

vowel in a form like a~bu!ro~ ‘younger sibling’, no assimilation results: a~bu!o~ (*a~bo!o~/*a~bu!u~). These cases differ in their foot structure (see O¢la 1995), a prosodic difference that may in-teract with the constraints on assimilation to produce the observed results.

28 See Awobuluyi (1967) on front/back harmony and Bamgbos¢e (1967), Awobuluyi (1967), Archangeli & Pulleyblank (1989, 1993, 1994), etc. on tongue root harmony.

Yoruba vowel patterns 33

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