The
discussion on how phonemic representations of utterances are ralaised
phonetically included an example from the African Ganaian language Akan, to
show that relationship between a phoneme and its allophonic realisation may be
complex. The same phone may be an allophone of two or more phonemes, as [m] was
shown to be an allophone of both /b/ and /m/ in Akan. We can also illustrate
this complex mapping relationship in English. Consider the vowels in the
following pairs of words :
In
column A all the boldface vowels are stressed vowels with a variety of
different vowel phones; in column B all the boldface unstressed vowels are
pronounced [ə]. How can one explain the fact that the same root
morphemes that occur in both words of the pairs have different pronunciations ?
In chapter 3, on morphology, we defined a morpheme as
a sound-meaning unit. Changing either would make a different morpheme. It does
not seem plausible (nor is it necessary) for speaker of English to represent
these root morphemes with distinct phonemic forms if there is some general rule
that relates the stressed vowels in column A to the unstressed schwa vowel [ə]
in column B.
Speaker of English know (unconsciously course) that
one can derive one word from another by the addition of derivational morphemes.
This is illustrated in the preceding list by adding –ition or –ance to verb
roots to form nouns, or –al and –ic to nouns to form adjectives. In English the
syllable that is stressed depends to a great extent on the phonemic structure
of the word, the number of syllables, and so on. In a number of cases, the
addition of derivational suffixes changes the stress pattern of the word, and
the vowel which was stressed in the root morpheme becomes unstressed in the
derived form. (The stress rules are rather complex and will not be detailed in
this intoductory text.) When a vowel is unstressed in English it is pronounced
as [ə], which is a reduced vowel.
All the root morphemes of column A are represented
phonetically by their value when stressed. A simple rule predicts that their
vowels are changed to [ə] when unstressed. We can conclude than that [ə] is an
allophone of all English vowel phonemes. The rule to derive the schwa can be
stated simply as :
Change a vowel to a [ə] when it is unstressed.
This rule is oversimplified, because when an
unstressed vowel occurs as the final segment of some words it retains its full
vowel quality, as shown in words such as confetti, motto, or democracy. In some
dialects, all unstressed vowels are reduced.
The rule that reduce unstressed vowels to schwa is
another example of a rule that changes feature values.
In a phonological description of a language that we do
not know, it is not always possible to determine from the phonetic
transcription what the phonemic representation is. However, given the phonemic
representation and the phonological rules, we can always derive the correct
phonetic transcription. Of course, in our internal, mental grammars this
derivation is no problem, as the words are listed phonemically and we know the
rules of the language.
Another example will illustrate this aspect of
phonology. In English, /t/ and /d/ are both phonemes, as illustrated by the
minimal pairs tie/die and bat/bad. When /t/ or /d/ occurs between an stressed
and an unstressed vowel it may become a flap [ɾ]. For many Australians
and most Americans, writer and rider are pronounced identically as [raɪɾə];
yet these speakers know that writer has a phonemic /t/ because of write /raɪt/,
whereas rider has a phonemic /d/ because of ride /raɪd/. The ‘flap rule’ may be
stated as :
An alveolar stop becomes a voiced flap when preceded
by a stressed vowel and followed by an unstressed vowel.
We are omitting other phonemic details that are also
determined by phonological rules, such as the fact that in ride the vowel is
lightly longer than in write because it is followed by a voiced [d], which is a
phonetic rule in many languages. We are using the example only to illustrate
the fact that two distinct phonemes may be realised phonemically as the same
sound.
Such cases show that we cannot arrive at a
phonological analysis by simply inspecting the phonetic representation of
utterances. If we just looked for minimal pairs as the only evidence for
phonology, we would have to conclude that [ɾ] is a phoneme in English
because it contrasts phonetically with other phonetic units: riper [raɪpə],
riser [raɪzə], and so forth. Grammars are much more complex than this pairing
shows. The fact that write and ride change their phonetic forms when suffixes
are added shows that there is an intricate mapping between phonemic
representations of words and phonetic pronunciations.
Notice that in the case of the ‘schwa rule’ and the
‘flap rule’ the allophones derived from the different phonemes by rule are
different in features from all other phonemes in the language. That is, there
is no /ɾ/ phoneme,
but there is a [ɾ] phone.
This was also true of aspirated voiceless stops and nasalised vowels. The set
of phones is larger than the set of phonemes.
The English ‘flap true’ also illustrates an important
phonological process called neutralisation; the voicing contrast between /t/
and /d/ is neuralised in the specified environment between a stressed and an
unstressed vowel.
Similar rules showing there is no one-to-one relation
between phonemes and phones are found in other languages. In both Russian and
German, when voiced obstruents occur at the end of a word or syllable, they
become voiceless. Both voiced and voiceless obstruents do occur in German as
phonemes, as is shown by the minimal pair below. Note that, in German, nouns
are capitalised in written form.
Tier [ti:r] ‘animal’
Dir {di:r] ‘to you’
At the and of a word, however, only [t] occurs; the
words meaning ‘bundle’, Bund /bʊnd/, and ‘colorful’, bunt /bʊnt/, are phonetically
identical and pronounced [ʊ`nt].
The German devoicing rule, like the vowel-reduction
rule in English and the homorganic nasal rule, changes the specifications of
features. In German, the phonemic representation of the final stop in Bun is
/d/, specified as [+ voiced]; it is changed by the rule above to [- voiced] to
derive the phonetic [t] in word-final position. This rule in German further
illustrates that we cannot decide what the phonemic representation of a word
is, given only the phonemic form; [b`ʊnt] can be derived form either /bʊnd/ or
/bʊnt/. However, given the phonemic representatioms and the rules of the
language, the phonetic forms are automatically derived.
