Lips, tongue, brain?

It is obvious that 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 very few say hot and mud or time and door with the T and D replaced in anything like the same way. Somehow the L sound at the end of little and middle disrupts the previous sound, whether it is T or D. But it is not obvious what is going on here. Is this by mishearing the words? Or by getting the tongue in a wrong position for one or more of the sounds? Various analyses have been proposed.

In all human populations, a proportion of individuals have problems with speech. In some it is screamingly obvious. In others it often passes unnoticed.

Sometimes the parents of a child with a speech and language issue ask themselves: Is my child brain-damaged? That can be a tough question.

In my experience, if the question is about the working of the brain as a whole, and the child has no other problem or problems, the answer is usually: No. But that is often a rather incomplete answer, because it may not really get to the essence of the question. To answer this question in any particular case, it is necessary to think of the child as an individual in a way that can only be done face to face, and certainly not in the abstract on the internet. Any attempt to give a general answer would be quite unethical in my view.

And the notion of damage may be too strong. The human brain represents the most complex entity in biology with a large number of interacting parts. So any one part can work relatively well or poorly for any one individual. And if it is working poorly, it can often be helped to work better.

Over the past century it has become clear that speech involves a large number of muscles from the lungs to the lips. A muscle is activated from the brain by a signal passing along a pathway. The longer the pathway between the brain and the muscle, the longer this takes. Long pathways have to be initiated before short ones. Almost all speech is on breathing out. The muscles of breathing, mainly the diaphragm and the muscles between the ribs, known as ‘intercostals’, are controlled by a different part of the brain from the muscles of the tongue and lips. So the messages to start breathing out have to be sent out by the brain some time before the first message for the first full-of-breath word. But all of this musculature has to be co-ordinated.

Making things more complicated, some of the ordering is in reverse. In English, as in classical Latin and many, but not all, modern European languages, the stress system (or the metricality or prosody) works from right to left. If what is known as the ‘scansion’ for stress did not work from right to left, English speakers might be confused about how to say Austria, America, Amazonia, with the stress on the first, second and third syllables from the left. The last of these is not familiar to all English-speakers. But there is no doubt about how to say it, because in all of these cases, scanning from right to left, the stress falls on the third syllable from the right. And the same principle of right-to-left scansion applies to the names of newly created drugs. The stress doesn’t need to be spelt out on the label. The same principle applies to every word in English apart from a very small number of words, mostly recent loans and names of revered foreign celebrities.

The system at play here has been exploited by poets writing in metre, from Chaucer, Shakespeare and Dryden, to the present.

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.

But the musculature of speech is not just by instruction. There are also feed-back processes, checking the effects of the instructions, by listening to these effects and by feeling what is happening, where the tongue is in the mouth, whether it is touching the roof of the mouth, and so on. Fractional adjustments are made to the instructions according to the results by the feedback. The co-ordination of instructions and feedback is obviously intricate. The effect of any disruption of this feedback is obvious after a pain-killing injection by the dentist or by trying to talk if the sound of the speech is artificially delayed, as sometimes happens on a mobile phone. Speech gets disrupted, or becomes impossible.

In some cases, the chain of instructions is disrupted by a medically well-defined condition like cerebral palsy or physical trauma. Here there may be no linguistic issue of any sort.

And some children’s issues do seem to be exclusively motoric, as, for example, where the activity of one invisible muscle in the tongue triggers a corresponding activity of a highly visible muscle in the face. But on the basis of my experience and research, where there is no discoverable medical factor, such exclusively motoric issues are rare.

So there is an obvious question about how far speech is just by instructions and adjustments, as is sometimes suggested, and how far there is also an irreducible linguistic aspect. To my way of thinking, some processes are forcibly linguistic rather than physical and perceptual. For instance, want to shortens to wanna only if there is a following word. “Do you wanna go? Do you really want to?” Like D and T before a syllabic L, the articulation of the T at the end of want and at the beginning of to looks forward to what is coming next. Such looking forward can’t be perceptual. And it isn’t plausibly motoric. On such grounds, it seems to me that linguistic factors are forcibly involved, and that children are normally learning about these seemingly small details at a very early stage in their acquisition of speech and language.

Children hear words for interesting things like animal, excavator, helicopter, kindergarten, hippopotamus. And they want to say these words too. The rhythm in all English words of two syllables or more is built about what were nicely called ‘feet’ in the ancient world. In English, as in classical Latin, a foot typically has a stressed syllable followed by an unstressed syllable. This is separate from the idea of a word.

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 putting the initial P in a word like pea or the initial F in a word like four together with what comes after. So from the end of the 1950s the idea started to grow that in order to properly understand speech disorders it was necessary to go beyond the notion of ordered speech sounds, to describe the integration of a larger system as a whole. So the idea developed of extending the neurological notion of apraxia, a sort of disorder which can occur after a stroke, by which someone can brush their teeth but not raise their hand to their mouth. A milder form of neurological apraxia is known as dyspraxia. By applying this notion of neurological apraxia or dyspraxia to speech, the idea developed of ‘Developmental dyspraxia’ or ‘Childhood Apraxia of Speech’ or CAS, as this is mostly known nowadays by speech pathologists. By this theory in one commonly developed form, it is now assumed that the disorder is in the motor-planning of speech – in the sequencing of the instructions.

It is obvious and incontestable that there is a motoric aspect of speech. The whole, incredibly complex apparatus, has to be moved, co-ordinated, and continually adjusted with extreme precision. The engineering is extraordinary.

But for children who cannot say pea or four, it seems to me more economical to hypothesise that their problem is in not connecting up the parts of the syllable, the beginning (or what linguists call the ‘onset’) and what linguists call the ‘rime’ or ‘rhyme’ (the vowel and any following consonants), than to hypothesise an entirely separate notion of ‘motor planning’, which does not throw any clear light on the considerable complexities of either word stress and its effects or on the derivation of contraction in wanna from want to.

Nor does the notion of motor planning throw any light on the range of characteristic ‘co-morbidities’, or the way 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 cluster together. This is to say that speech and language problems tend to be complex. For instance, most dyslexic children have also had problems learning to talk. Most children who are hard to understand or have difficulties with literacy 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?

Some languages, but not all, have a complex rhythm inside the word. So in English there are two stresses in words like hippopotamus, with the stress in the rightmost foot stronger than the stress in the leftmost, and with the final syllable discounted in the computation of this. These are things which children learning English normally start learning between one and a half and two and a quarter – that features, phonemes, the syllable, the word, the stress pattern, and the foot structure, are all different things. For some children, this learning is not easy.

In my experience, 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.)

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.

So I am what is sometimes referred to as a ‘CAS skeptic’. But to my mind the real skepticism is not about CAS, but about linguistics.

I personally think that CAS (also often referred to as ‘dyspraxia’) is unfortunately somewhat over-diagnosed, and that well-evidenced linguistic categories provide better, more precise guidelines for effective treatment.