Listening to children with speech disorders, it is obvious that for some of them at least the issue is not just one of individual speech sounds. For instance, some children have difficulty joining the P in a word like pea to what comes after or the F in a word like four. So from the end of the 1950s, the idea started to grow that in order to properly understand such speech disorders it was necessary to go beyond the notion of disordered speech sounds, and to think in terms of the disintegration of a whole system. And the idea developed of extending the neurological notion of ‘apraxia’, a disorder which can occur after a stroke, by which someone can brush their teeth but not raise their hand to their mouth, to a notion of ‘motor-planning’ for speech. This is now widely known as Childhood Apraxia of Speech or CAS. (Or ‘dyspraxia’ by an older terminology.) But this is a bit naughty. On a neurological understanding, apraxia is not about a lack of co-ordination within one system. It’s about a failure to connect two separate systems – of voluntary and involuntary movement – something obviously quite different.
The importance of definition
It is obvious and incontestable that there is a sensori-motor aspect of speech. A complex apparatus from the lungs to the lips has to be moved, co-ordinated, and continually adjusted with extreme precision. And habit is obviously a factor here. But to describe the speech of children who cannot say pea or four, it seems to me unnecessary to invoke a special notion of motor planning when there is a more precise and economical description in terms of the syllable, as this has been understood for the last two thousand years. On this basis, there is a not uncommon problem consisting in a failure to connect up the parts of the syllable, the initial consonant or consonants and the vowel and any following consonants.
By a less common problem, a child can say MOO but not me, saying EE instead, and saying knee correctly, but not NOO, saying OO instead. Both the consonant and the vowel in MOO involve the lips, so this can be said by treating the whole syllable as a single entity. Conversely, neither the consonant nor the vowel in knee involve the lips, so this can be said too. But where there is a difference with respect to the lips, as in NOO and me, only the vowel can be pronounced, and the syllable becomes unpronounceable. In other words, the initial consonant is treated as a mere extension of the vowel. The syllable is treated as special sort of vowel which can have an N or M in front of it, according to whether both or neither involve the lips.
A syllabic account of such problems seems to me more precise than invoking the very broad notion of ‘motor planning’ for which the only justification is in relation to disorder.
The notion of CAS overlooks the fact that a word is not just a series of muscular articulations or transition between syllables, but part of a hierarchy of structures including speech sounds, or phonemes, as well as phrases and sentences. So, for example, what happens to a D before an M in competently spoken adult English varies according to whether this in a phrase like good morning as a greeting with the D often becoming a B or between sentences as in “Good. Many of us are in the same boat.” with the D usually remaining a D.
I recognise what is meant by the term CAS. But to me, it diverts clinical attention from the most relevant details. So I don’t use it myself. Those like me who have issues with the idea of CAS are often called ‘CAS sceptics’. But the true skepticism, I believe, is about linguistics.
A linguistic approach has, I submit, four things going for it. First, it reconnects with the first 350 years of clinical linguistics, as by the work of the last three members of my awesome foursome. Second, it offers an accurate way of scaling degrees of need, for instance between children who are having problems connecting up the parts of syllables and those who are treating syllables as speech sounds or ‘phonemes’. Third, it accounts for the fact that different sorts of speech and language issues often go together. These are known as ‘co-morbidities’, and are otherwise unaccountable. Fourth, it helps to decide which of a child’s problems to address when.