There are two perspectives on human speech. One emphasises the physicality. From this perspective, children’s characteristic incompetences can be characterised in terms of ‘processes‘. This perspective stems from the ancient assumption that speech is the business of the tongue and the lips. From another perspective, speech (or signing in the case of a signed language) is the external expression of the faculty of human language, something evidently mental and cognitive, the business of mind and brain.

From normal immaturity to pathology

From both of these perspectives, the mental and the physical, there is an issue of how to encompass the whole range of disorder, from one or more incorrectly pronounced speech sounds to unintelligibility.

As a normal immaturity, little is often said as LIKU, and middle as MIGU.

As a characteristic pathology, some children can’t join the P in  pea or the F in four to the following vowel to form the simplest sort of syllable. By a more serious pathology, some children can say MOO but not me, saying EE instead, and knee correctly, but not no, saying OH instead.

In the 1950s, there were two main therapeutic responses to this perception of speech disorders going beyond  defects in the gesturing of single speech sounds, both focusing strongly on the physicality of speech.

Oral Motor Therapy – OMT

One of these responses was to focus exclusively on the actual movement of the articulators. There are many energetic and convinced proponents of several variants of this idea. One variant is known as ‘oral motor treatment’ or OMT. Characteristically, it involves 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’. OMT promotes exercises supposedly increasing the strength of the musculatures in the mouth and jaw stability. Some of the exercises recommended like prolonged tongue protrusions, wagging the tongue from side to side, drawing the tongue backwards along the floor of the mouth, have no obvious justifications from phonetics. 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.

Childhood Apraxia of Speech – CAS

The other response sought to extend the neurological notion of ‘apraxia’ to the notion of developmental speech disorders. Apraxia is a neurological disorder, typically after a stroke or some other major trauma to the brain, by which someone can brush their teeth but not raise their hand to their mouth. 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.)

If the CAS 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, with the main stress in Austria, Australia, and Amazonia, in all cases on the third syllable from the right, and in the cases of little and middle, again computed from right to left, but in both cases finally landing on the initial syllable. But the complexities here are ignored by the theories of CAS and OMT.

Scepticism

In relation to both sorts of theory, of OMT and CAS, in the relatively normal cases of little and middle, first a tongue-tip T or D dissimilates to a back-of-the-tongue K and G, next to a tongue-tip L, where the L is  functioning as the nucleus of a final unstressed syllable. Here one distinctive feature displaces another. In this case the features involve different points at which the tongue blocks the oral cavity – by the tongue tip or the back of the tongue. The unstressed L sound on the right forces the preceding sound to become more different, increasing the contrast between two sounds. Second, the L becomes more vowel-like, more like the OO of foot, losing all of the original tongue-tip quality. The stress has to be defined before the articulation of the T or D in the ‘onset’ of the syllable. In the more obviously pathological case of children who say pea as EA, the whole syllable is treated as one entity, with the initial consonant, a mere extension of the vowel. In the more serious case of children who cannot say me or no, again the whole syllable is treated as an entity, but without any differentiation between the syllable and its nucleus. In  little and middle, there is a problem from the ordering of the derivation. In pea and me, there are problems with the definition of the categories within the syllable, greater in the second case than in the first. But none of these symptomatologies can be conceptualised in exclusively articulatory or motor terms. They all require reference to higher order categories involving stress, syllabicity, and feature identity.

To me, the notions of both OMT and CAS divert clinical attention from the most relevant linguistics – particularly the interaction between segmentality and metricality.

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.

Those who do not subscribe to the quite complex theoretical apparatus postulated by CAS proponents are often labeled ‘CAS sceptics’. But as one of the so-called sceptics, I believe that CAS proponents misconstrue speech in almost exclusively physical terms. It is they who are the sceptics – about linguistics.

A biolinguistic alternative

What exclusively physical approaches to speech disorders overlook is that speech is subject to several interacting hierarchies of principles defining both meaning and rhythm. These include the structure of what are known as ‘feet’ like the two feet in calculator, CALCU and LATOR. computed first from right to left. for the primary amd secondary stresses on LA and CAL, and then within these feet from left to right.

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. And the disorder is the result of the lack of definition.

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

• Reconnecting with the first 350 years of clinical linguistics, as by the work of Holder, Thelwall and Bell.
• Offering an accurate way of scaling degrees of need and progress in therapy. Some children have problems connecting the syllables. Others have problems connecting up the parts of syllable, ignoring foot structure, the speech sounds, their features, the phonotactics, and more,
• Accounting for the characteristic co-morbidities or multifactorialities of speech and language disorders, such as the fact that most children who are hard to understand,  have difficulties with literacy, and are not good at telling what counts as a possible word, known as ‘metalinguistics’. If speech problems are characteristically motoric, how is that they so often co-occur with poor metalinguistics, an issue which is plainly not motoric, but cognitive?
• Helping to decide which of a child’s problems to address when.
• Being more precise than is possible by the notion of ‘motor planning’ for which the only justification is in relation to disorder.
• Avoiding the need for distinctions between many categories of 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.) I personally think that CAS (also often referred to as ‘dyspraxia’) is seriously over-diagnosed, and that well-evidenced linguistic categories provide faster, more precise guidelines for effective treatment. 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.

What one language prohibits, another permits. And for some children the evidence available is not clear or sufficient. 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 child with a problem saying me and no may be not just confusing categories within the syllable, but making a mistake about what sort of language English is.

Care, not recklessness

At the same time, to throw away all thoughts about what biolinguistics calls the Articulatory / Perceptual (or A/P) interface would be absurd and irresponsible.  The A/P interface is real, and critically involved in some disorders, I think, including stammering, as by Nunes (1994).