5.4 DIFFERENCES BETWEEN LEXICAL AND POST- LEXICAL RULES
As we saw in [5.7], the lexical morphology and phonology model has two compartments, the lexical and the post-lexical. So far, we have only considered rules in the lexical compartment. We have seen that the func- tion of lexical rules is to build word-structure and we have emphasised the fact that they appear on two strata in the lexicon.
We are now going to examine the other compartment in the model which
Differences Between Lexical and Post-Lexical Rules 107 contains post-lexical rules. There are a number of key differences between lexical and post-lexical rules. I will highlight four.
(i) Post-lexical rules can apply across word boundaries
Whereas lexical rules only build words in the lexicon, post-lexical rules apply to words after they have been formed in the lexicon, and processed through the syntax. While the maximum domain of application of lexical rules is the word, post-lexical rules can apply, across word-boundaries, to words after they have been grouped together into phrases. Hence the post- lexical phonological rule system is also called phrasal phonology.
An example of a post-lexical rule applying across word-boundaries is the rule that optionally deletes a word-final alveolar stop in a consonant cluster if the next word begins with a consonant as in [5.27]:
[5.27] last trip na:st tnp/ [ /lo:st tnp] or [ na:s tnp]
lost property nost prop;:) til [lost prop;:)ti] or [los prop;:)ti]
(ii) Lexical rules are cyclic
As we have already seen, lexical rules are cyclic in the sense that at each stratum in the lexicon, it is necessary to make a pass through both the morphological and phonological rules which go with them. By contrast, post-lexical rules are not cyclic. There is no similar linkage of pairs to syntactic rules with phonological rules.
(iii) Lexical rules must be structure-preserving
This means that the output of each layer of derivation must be a word. A lexical rule may not produce a form that could not be a phonologically well-formed word in the language.
There are canonical phonological patterns (i.e. standard patterns) of seg- ment structure, syllable structure and prosodic structure that severely restrict the kinds of morphemes and words that can appear in the lexicon of a language.
(a) Obviously, there are restrictions on segments that can appear in words of a language. Thus, the putative word /a asp/, which begins with an alveolar implosive /a/, is ruled out because implosives are not part of the phoneme inventory of English.
(b) Lexical rules must not produce forms that violate phonotactic con- straints on the canonical syllable structure patterns in a language (see 4.1.1). Thus *ltarpment nto:pm;:)nt/ and *tsem /tseml are not possible English words since [It] and Its/ are prohibited consonant sequences in syllable (and word) initial position (though, of course, both are allowed syllable finally as in melt /melt/ and sets /sets/).
(c) Every lexical item must have one main stress. So, no lexical rule may create a word like *'presta'pping which has two main stresses.
108 Introducing Lexical Morphology
By contrast, post-lexical rules are not subject to any structure-preserving constraint. They may have an output that is at variance with the canonical patterns of the language. For instance, though no word in the lexicon can begin with [ts], this sequence may occur phonetically when two words come together in utterances, in casual speech if vowels get elided, as in:
[5.28] [tsnnt]
[tsbaut]
[tsrem]
'it's not' 'it's about' 'it's Sam'
(iv) Post-lexical rules are automatic but lexical rules are not
Whereas lexical rules are exception-ridden, post-lexical rules are automatic and apply without exception to all forms with the requisite phonetic properties, regardless of any morphological properties. For our present purposes, by automatic I do not mean obligatory. Some post-lexical rules may be optional. Rather, by automatic I mean that if the necessary phonetic conditions are present, the rule can apply. There are no specific words or grammatical contexts in which its application is blocked.
There is hardly a lexical rule that applies to all the forms that it could affect in principle. We have already seen the unpredictability of word- formation processes in the lexicon, particularly at stratum 1. Thus, we cannot predict which bases will take the stratum 1 suffix -th, and which ones will not. We are allowed leng-th, bread-th, dep-th and wid-th, but not
*tall-th, *short-th, *thick-thor *narrow-th.
Even 'regular' stratum 2 lexical rules are not entirely predictable. For instance, the meaning of the stratum 2 regular plural inflectional suffix -s (as in books) is not totally predictable. There are non-count nouns ending in the plural -s suffix that are always treated as syntactically plural - even when singular in meaning, e.g. pliers, tights, trousers and shears. But non- count nouns like measles, rickets and mumps with the same suffix are normally treated as syntactically singular, though some people treat them as plural. Here we see that the phonological behaviour of -s may be predictable, but the meaning realised by it may not be.
In contrast, post-lexical processes are automatic in the sense explained above, i.e. they are not subject to lexical exceptions nor can they be blocked in certain grammatical contexts. I will illustrate the exceptionless nature of post-lexical rules by considering the glottalisation rule that produces a glottal stop allophone [?] of the phoneme It/ in many varieties of British English, as seen below:
[5.29] t ~ [?]
a. in word final position /'kret/ ~ ['kre?] 'cat' (noun)
lit/~ [1?] 'it' (pronoun)
/'bAt/~ ['bA?] 'but' (conjunction)
Exercises b. before a consonant
/'ketl) ~ ['ke?l] 'kettle' (noun) /'setll ~ ['se?l) 'settle' (verb) /'kretfif/ ~ ['kre?f1f) 'catfish' (noun)
c. between vowels - if /t/ is initial in an unstressed syllable /'wet';J/ ~ ['we?';J] 'wetter' (adjective)
/'mi:t';J/ ~ ['mi:?';J] 'meter' (noun' /'bot';Jm/ ~ ['bo?';Jm] 'bottom' (noun) /'put';J'bit';JV 'bAt';J/ ~ ['pu?';J 'bi?';J(v) 'bA?';J]
'put a bit of butter' (verb) (noun) (noun)
109
The glottalisation rule applies blindly without taking into consideration the particular word that the relevant It/ is in. This is typical of post-lexical rules. They apply anywhere so long as the phonetic conditions for their application are met.
Enough has been said to show that phonological rules applying in the lexicon, which are triggered by morphological rules, have different proper- ties from phonological rules that are found in the post-lexical compart- ment. This is important from a theoretical point of view. It is one of the planks in the argument for recognising morphology and the lexicon as a separate component in our theory of language. But as our concern here is what happens in the lexicon, no more will be said about post-lexical rules.
EXERCISES
1. Study the following data:
Suffix
- - attach to Output
-aV(i)aV( u )al [autumn ]-al] ~ autumnal [medicine ]-al] ~ medicinal [contract-(u)al] ~ contractual [resident ]-(i)al] ~ residential [provinc]-ial] ~ provincial [sens]-ual] ~ sensual -(ac)y [democrat]-acy] ~ democracy
[supreme ]-acy] ~ supremacy
-er [London]-er] ~ Londoner
[ village-er] ~ villager
-er [hat]-er] ~ hatter
[slate]-er] ~ slater
110 -er -er
Introducing Lexical Morphology [run)-er]s]
[sing]-er]s]
[quick)-er]
[clean ]-er]
runners singers quicker cleaner
(a) For each example determine the word-class of the bases that form the input to the suffixation process and the word-class to which the resulting word belongs.
(b) At what stratum in the lexicon is each one of these suffixes found?
Justify your answer.
2. (a) From which languages did English borrow the words in the two sets below?
(b) Identify the number of suffixes in these words.
(c) At what stratum in the lexicon is each plural suffix added? What is your evidence?
SetA SetB
Singular Plural Singular Plural
stimulus stimuli phenomenon phenomena
fungus fungi criterion criteria
syllabus syllabi ganglion ganglia
radius radii automaton automata
3. At what stratum are the nouns cook, guide and cheat derived from the corresponding verbs? On what basis does one decide?
4. Write formal morphological rules using the notation introduced in this chapter to account for the formation of the past tense of the following verbs: moved, baked, ran and hit.
6 Insights from Lexical Morphology