Some
phonological rules are neither assimilation nor dissimilation rules. The
aspiration rule in English, which aspirates voiceless stops at the beginning of
a syllable, simply adds a non-distinctive feature. As we did in the
nasalisation rule earlier, we can use the symbol $ to represent a syllable
boundary. Generally, aspiration occur only if the following vowel is stressed.
The /p/ in pit and repeat is aspirated but the /p/ in in $ spect or com $ pass
is usually unaspirated (although if aspirated it will not change meaning since
aspiration is non-phonemic). Using the feature [+ stress] to indicate a
stressed syllable and V` to symbolise stressed vowels, the aspiration rule may
be stated:
Aspiration
is neither present nor absent in any phonemic feature matrices in English.
Assimilation rules do not add new features but change phonemic feature values,
whereas the aspiration rule adds a new feature not present in phonemic
representations.
Remember
that /p/ and /b/ (and all such symbols) are simply cover symbols that do not
reveal the phonemic distinctions. In the phonemic and phonetic feature
matrices, these differences are made explicit, as shown in the following
phonemic matrices:
The
non-distinctive feature ‘aspiration’ is not included in these phonemic representations
because aspiration is predictable.
