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‘Childhood Apraxia of Speech’ – lips, tongue, brain

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.

Many, perhaps most, children go through a stage of saying little and middle with the L as something like OO and the T of little as K and the D of middle as G. But some children have more fundamental problems, such as being unable to join the P in  pea or the F in four to the following vowel to form the simplest sort of syllable, or being unable to say a word like milk involves three articulations, with the lips, the tip of the tongue and the back of the tongue, or being able to say MOO but not me, saying EE instead, and saying knee correctly, but not NOO, saying OO instead, treating the whole syllable as a single entity. treating the initial consonant as a mere extension of the vowel.

In the 1950s, two therapeutic responses emerged, both reflecting the ancient assumption that speech is the business of the tongue. One of these responses sought to extend 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 the notion of developmental speech disorders. Following this logic, a predominant issue in speech disorders is assumed to lie in the ‘planning’ and ‘execution’ of the motoric gestures of speech within the the most peripheral part of the vocal tract, the tongue and the lips. So this is known as Childhood Apraxia of Speech or CAS. (Or ‘dyspraxia’ by an older terminology.)

But if the theory of planning and execution is correct it has to work simultaneously in both directions from left to right and from right to left. Word-stress in English, as in many languages, is computed from right to left. In large measure, the scansion for stress works independently from the speech sound system. But not completely, as in the case of words like little and middle. The T of little and the D of middle are pronounced in particular ways because of the unstressed L sound on the right which is unstressed because it amounts to a syllable in its own right. In English only unstressed syllables work like this. And this is presumably a difficult thing to learn because so many children have difficulties on this point. Stress has a huge effect on both the energy of articulations and sometimes, as in the T and D of little and middle, on whether they are completed. The theory of CAS just ignores all of this.

The other response was to focus exclusively on the actual movement of the articulators, particularly the tongue and the lips. There are many energetic and convinced proponents of what they call ‘oral motor treatment’ or OMT involving a variety of exercises for ‘jaw stability’ or the strength of the tongue, flicking it up and down, wagging or waving it from side to side or moving it round in circles. Various devices are on sale to help in such endeavours.

Caroline Bowen (2005) and Greg Lof (2006) show there is little or no evidence to justify OMT. To the best of my knowledge, there is no evidence from phonetics for any of the categories which OMT claims to address, such as ‘jaw instability’ or ‘tongue weakness’. But The corresponding categories may simply not exist. The mind and meaning, the linguistics, acquisition, learnability are all set on one side. I believe that the claims made for these treatments are either mistaken or fictitious.

It is, of course quite possible that there will be improvements after a sensitively administered program of exercises. And this may be taken to justify the exercises. But it is also possible that the critical factor here is the sensitivity of the administration rather than the exercises themselves.

But what both of these almost exclusively physical approaches to speech disoreders overlook is that speech is not just a series of muscular articulations, but part of a hierarchy including foot structure, phrases and sentences. What one language prohibits, another permits. And for some children the evidence available is not clear or insufficient. For instance. many languages divide their vowels into those which are pronounced with the airstream through the nose and those with the airstream passing only through the mouth. A chilod with a problem saying me and NOO may be making a mistake about what sort of language English is.

A biolinguistic alternative

It is obvious what the term CAS seeks to characterize. To describe the speech of children who cannot say me, pea, four, or milk, it seems to me unnecessary to invoke a special notion of motor planning, strength or stability, when there are more precise and economical descriptions in terms of syllables and other linguistic structure. If these things are entirely undefined in the mind of the child, there is nothing to be connected up. To me, the notion of CAS diverts clinical attention from the most relevant details.

A linguistic account of such phenomena seems to me superior in six ways.

First, it reconnects with the first 350 years of clinical linguistics, as by the work of my child centered five.

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 apparently separate issues with clarity of speech, using the grammar of complex sentences, learning to read and write, and being able to recognise similarities in the sounds of words often go together. For instance, most children who are hard to understand,  have difficulties with literacy, and are not good at telling what counts as a possible word. If speech problems are characteristically motoric, how is that they so often co-occur with a poor awareness of words and sounds, an issue which is plainly not motoric, but strictly cognitive?These apparently separate issues are known as ‘co-morbidities’, and are otherwise unaccountable.

Fourth, a linguistic account helps to decide which of a child’s problems to address when.

Fifth, linguistic description is more precise than invoking the very broad notion of ‘motor planning’ for which the only justification is in relation to disorder. Unless there is a clear medical diagnosis suggesting otherwise, the overwhelming majority of speech disorders can be described in terms of linguistic categories, independently well-defined by normal speech, rather than inferred from disorder. (In science it is generally thought better to define categorisations by normal and correct function rather than by dysfunction.)

Sixth, it is simpler.

To throw away all of the categorisations by normal and correct function in favour of the much vaguer idea of a failure of praxis or motor-planning seems to me both an error in science and a therapeutic disadvantage.

I personally think that CAS (also often referred to as ‘dyspraxia’) is unfortunately somewhat over-diagnosed, and that well-evidenced linguistic categories provide faster, more precise guidelines for effective treatment. Those like me who have issues with the idea of CAS are often called ‘CAS sceptics’. But the true skepticism, I believe, is with respect to linguistics. To throw away all of the categorisations by normal and correct function in favour of the much vaguer idea of a failure of praxis or motor-planning seems to me both an error in science and a therapeutic disadvantage.

At the same time, to throw away all thoughts about what generativists call the Articulatory / Perceptual (or A/P) interface would be reckless.