Phonology: case studies

A mora-based analysis

In the last sections, we presented an analysis in which three different cases of compensatory lengthening were derived by rules that delete a consonant and lengthen the vowel preceding that consonant. Having the CL rules express both changes in this way captures the intuition that the vowel lengthening and consonant loss are connected, though it does not explain why. The CL rules also assume that vowel lengthening and consonant deletion are simultaneous (as opposed to sequential) although it isn't clear why this should be the case. In the last section, we discussed a number of reasons we might want to treat deletion and vowel lengthening as products of different rules, but showed that making this separation led to difficulties in accounting for the facts.

In this section, we briefly present an analysis that captures the connection between consonant deletion and vowel lengthening directly while at the same time treating them as distinct sound processes.

The idea we discussed at the very beginning of this module on compensatory lengthening was that vowel lengthening compensates for a consonant that has been deleted. We might well have questioned the sense of such an idea: if a phonological segment is deleted, then isn't it just gone? If it's gone, why would another segment be lengthened to make up for its loss? It is as though when the consonant is deleted, its "ghost" remains in the phonological representation.

The "ghost" phenomenon associated with compensatory lengthening is one among several reasons why phonologists have argued that some phonological segments are associated with "timing slots" in the phonological representation. In the most widely accepted version of this theory, advanced in Hayes (1989), vowels are always associated with timing positions, which are called morae, or moras (from the singular mora). Short vowels are universally represented as having one mora, and long vowels have two, as shown in (29a) and (29b). In some languages, a consonant can be assigned a mora based on its position in the syllable. In languages that do this, a syllable final consonant is assignment a mora, shown in (29c), but consonants in the onset of a syllable are not moraic. In other languages, consonants are never assigned moras, and coda consonants are treated as dependents of the last mora of the preceding vowel as shown in (29d).

(29)	Syllable types and their moraic structure

a.	Short vowels	b.	Long vowels	c.	Moraic codas	d.	Nonmoraic codas
	σ		σ		σ		σ
	|		/\		/\		|
	μ		μμ		μμ		μ
	|		\/		| |		|\
	C V		C V		C VC		C VC

If we adopt the view of syllable structure just described, a more straightforward and intuitive analysis of compensatory lengthening is possible. Consider that in the cases where the deletion of a consonant is accompanied by CL, the deleting consonant occurs before another consonant, indicating that it was in the coda of a syllable. In the cases where deletion is not accompanied by vowel lengthening, the deleting consonant stands before a vowel (before being deleted), indicating that it is in the onset of a syllable. This is important, because in the model of the syllable illustrated above, coda consonants may have moras, but onset consonants never do. We can represent compensatory lengthening as in (30). At a pre-CL phase, (30a), a consonant is parsed as the coda of a syllable, and (in a language like Turkish), is assigned a mora. (Hayes 1989 refers to this process as weight-by-position.)

(30)	A moraic analysis of compensatory lengthening

a.	Pre-CL	b.	C deletion	b.	V lengthening
	σ		σ		σ
	/\		/\		/\
	μ μ		μ μ		μ μ
	| |		|		\/
	VC		VØ		V

As an illustration, the diagrams in (31) show the syllable structures we assume for the forms ovdu 'rub (past)' and ovar 'rub (aorist)', as they occur in formal speech settings, in which consonant deletion does not occur. The diagrams in (32) provide representations for the informal speech forms, which have undergone consonant deletion and compensatory lengthening.

(31)	Formal speech variants: no deletion / CL.

σ		σ		σ		σ
/\		|		|		/\
μ μ		μ		μ		μμ
| |		|		|		| |
o v	d	u	'rub (past)'	o	v	a r	'rub (aorist)'

(32)	Informal speech variants: consonant deletion and CL.

σ		σ		σ	σ
/\		|		|	/\
μ μ		μ		μ	μμ
\/		|		|	| |
o	d	u	'rub (past)'	o	a r	'rub (aorist)'

The mora-based analysis of compensatory deletion we have developed in this section is superior to the previous analysis in a number of ways:

1. The moraic analysis separates the phenomena of consonant deletion and vowel lengthening, resulting in greater efficiency and generality:
   
   
   • The number of deletion rules is limited, and they generalize to all cases in which a given consonant is deleted, whether or not vowel lengthening occurs.
   • Only a single rule of vowel lengthening is required. Information specific to consonant deletion is factored out, so that the lengthening rule directly expresses the connection between the diffferent cases of CL.
   
   
2. The moraic analysis provides a more satisfying explanation of the CL phenomena, in that it explains why vowel lengthening sometimes accompanies consonant deletion. CL really is compensatory, in that lengthening fills a mora that has been vacated as the result of a deletion rule.
   
   
3. Finally, we have an explanation for why the deletion of a consonant vowel triggers lengthening in some cases and not others.
   
   
   • Vowel lengthening occurs when the deleted consonant stands before another consonant in the pre-deletion representation. In Turkish, any consonant standing before another consonant is in the coda of a syllable. Lengthening occurs in these cases because coda onsonants are a mora in Turkish. The deletion of a coda consonant therefore frees a mora, which is "picked up" by the preceding vowel, which lengthens to fill this mora.
   • Lengthening doesn't occur when the deleted consonant precedes a vowel in the pre-deletion representation. A prevocalic consonant is in the onset of a syllable, and onset consonants do not have moras.

As a postscript, we note that phonologists' use of the mora in phonology borrows from the traditional notion of the mora in poetry. In mora timed poetic forms, syllables with one mora scan as short, while syllables with two morae scan as long. In poetic forms of this type, one long syllable counts for two short ones for the purpose of satisfying length restrictions on a line.

prev | top