If you can see something is wrong with your child, you want to know what it is, and have it explained in terms you can understand. A diagnosis, in other words. The problem can be given a name. But that may fall short of a diagnosis.

If the development of speech and / or language is significantly delayed or disordered – and if it is, this is mostly obvious to professionals and non-professionals alike – because a child of three

• Has only one word;
• Or chatters away, but incomprehensibly;
• Or is completely silent;

AND there is no measurable hearing loss or anatomical defect or medical history pointing in some direction, and there is nothing visibly untoward in the family life, there is a natural question: What is causing the problem?

Here it is reasonable to start with the likeliest answer. If a blank is drawn with that, it is reasonable to go on to the next likeliest, and so on. But it is also important to take account of the DEGREE of abnormality. Only one word at three is severely abnormal. Only one word at two is just late.

Starting simple

In science there is an impetus to reduce the investigation to the smallest possible set of variables. But in speech and language this is uncommonly hard. There are medically diagnosable conditions including hearing loss, Down’s syndrome, autism and cerebral palsy, all affecting speech and language in different ways. But in the absence of any such diagnosis, the investigation of a disorder of speech or language can follow a number of directions:

There are the factors listed in the Check list here – including:

• The anatomy and functioning of the vocal tract;
• Attention;
• Memory of what has just been heard;
• Discrimination of a sound or words against background noise;
• Movements of the articulators;
• Whether or not language is used appropriately;
• How many words are known;
• Linguistic structuring of words and sounds;
• Phonetic accuracy;
• Awareness of words and sounds as such (metalinguistics);
• The will to communicate.

Some of these things can be reduced to numbers on scales. But there is a new factor here which plainly can’t be reduced to a number – the child’s experience of Covid.

An enormous volume of research has sought to disentangle the relative effects of the various competences here and how they interact. But it is very unclear how far any particular level of incompetence is likely to be critical.

Making sure not to miss anything

There is another question: Are there any other related capacities which are similarly affected? But there is no human capacity truly comparable to speech and language.

Common and not so common diagnoses

Various disorders are sometimes called ‘psycholinguistic’, ‘phenotypic’, ‘congenital’, ‘intragenic’, ‘idiopathic’ or ‘neurogenic’ , in some cases referring to a theory of the ’cause’. I list some here under the heading of ‘Speech and language therapy‘.

More than one issue

Some impairments commonly occur together. Some of them co-occur with more general learning disabilities. Issues that involve the clarity of speech often impact on literacy. Some of these issures were once known as ‘dyslalia’, but the term has dropped out of use in the English-speaking world. (It is still used in Eastern Europe.)

What is commonly known as ‘Childhood Apraxia of Speech or CAS’ or previously ‘dyspraxia’ seems to me over-diagnosed. ASHA (2008) reflects the same worry. My own and seemingly ASHA’s worry is sometimes characterised as ‘CAS scepticism’. I personally think that this characterisation reflects a lack of insight, and that the characterisation itself should more properly be as a general scepticism about linguistics.

Clinical Investigation

The diagnostic starting point, it seems to me, should be simple observation of what can be seen or heard, directly or indirectly, in the course of a ‘clinical investigation’, as Jean Piaget called it, but without excluding anything either. Seemingly small details can be critical. Children are normally learning about seemingly small details from the very beginning of their acquisition of speech and language. If they aren’t, that may be diagnostically significant.

Diagnosis and need

In respect of a given child there may be a number of diagnoses. There is no clear borderline, for instance, between what I would call a phonetic / phonological disorder and Childhood Apraxia of Speech. (Nunes (2019) sets out the significant issues here.) But it is very unlikely that there would be any disagreement between those making such different diagnoses over the need for treatment.