Saturday, 18 January 2014

Language disorders and reading difficulties - Same, same, but different?


The need to organise and categorise

Life would be unmanageably complex if we were not able to organise aspects of our environment and experiences into categories.  Sometimes categories and labels are imposed on us, e.g. gender, race and in some cases “class”, and can be a burden as much as an aid. But many are more fluid and can be organised (and re-organised) according to personal preferences. If you've ever tried to prepare a meal in someone else’s kitchen, for example, you will have seen that the way they group and organise utensils, appliances and crockery might be very different from the system that works so well for you at home. One is not necessarily superior to the other, but your system no doubt makes sense to you, as does your friend’s to him or her. Sometimes we are inspired by other people’s ways of organising a particular space or process and we “borrow” systems that look like they will make our own lives easier.

In its own way, this process of “working out what goes where” is not much different from the science of classification of illnesses and disease (“nosology”).  Nosology has been particularly important in psychology and psychiatry, because these disciplines, more than others in the clinical sciences, rely on clinician judgement about “what goes where”. Conditions such as schizophrenia and bipolar disorder, for example, are diagnosed not on the basis of blood tests or radiological scans, but through the process of pattern recognition by skilled and experienced clinicians. Pattern recognition, as the name suggests, involves a clinician carefully identifying what might seem like disparate clinical features (e.g. gradual social withdrawal, expression of “strange” ideas, and lack of sleep over many days) and asking if they have a likely unifying basis. This kind of thinking is sometimes referred to as applying Occham’s Razor, and is designed to protect against blinkered clinical reasoning and confirmatory bias in the process of differential diagnosis. An inexperienced clinician, for example, who placed undue significance on one of the features mentioned above (e.g. lack of sleep), could make a grave diagnostic error and is unlikely to develop an appropriate management plan. 

For many decades (but not uncontroversially!) the diagnostic systems used to assist in psychiatric decision-making have been the Diagnostic and Statistical Manual of the American Psychiatric Association (the so-called “DSM”, now in its 5th edition, as of 2013) and the World Health Organization’s International Classification of Diseases (now in its 10th edition, as of 2010, with the 11th edition due in 2015). The fact that the revision process for DSM-5 took many years and continues to be the subject of vigorous debate about what is “in” (e.g. some new categories, such as hoarding disorder), what is “out” (so-called Asperger’s Syndrome has been removed from this latest edition), and what has had its diagnostic criteria modified (e.g. substance abuse). As knowledge about and attitudes towards different conditions evolve, so too do the classificatory systems that sit around them.

If you’re still with me at this point, you would be forgiven for thinking that this post is about how language and learning disorders are treated in DSM-5, released last year.  That is an important and relevant issue, for speech language pathologists, psychologists, teachers, and parents alike, and if you’d like to know more about it, you can check out this ASHA Quick Guide. But no, I’d like to talk instead about the problems that occur when language and literacy are uncoupled from each other, conceptually, diagnostically, and educationally.

“Literacy is parasitic on language”

You probably haven’t thought of literacy as a “parasite” before – it’s certainly an evocative mental image. I first encountered this term when it was used in an open-access paper by Professors Maggie Snowling and Charles Hulme in 2012.  Without being too distracted by the microbiological features of a parasite, this analogy invites us to think about the symbiotic relationship between language and literacy, and the reliance of literacy on its “host”, i.e. a child’s underlying expressive and receptive oral language skills. With respect to the science of classification and its implications for language and learning difficulties, Snowling and Hulme made a persuasive case in this paper for what they referred to as “homotypic comorbidity” between language disorders and reading difficulties. This term draws on arguments in a 1991 paper by Carron and Rutter (also open access), who referred (in relation to the diagnostic classification process of childhood disorders more generally) to the idea that in some cases " disorder constitutes an early manifestation of the other" (p.1071).

The term "homotypic comorbidity" will be unfamiliar to many I suspect (it was to me), but I am sure that with some reflection, it will enhance the way we understand the relationship between language disorders and learning problems. I think of it this way:

In the pre-school years, there’s a sizeable proportion of children (estimates vary for a range of reasons, but let’s say for argument’s sake 20% across the board) whose oral language skills (expressive and receptive vocabulary, syntactic complexity, phonemic awareness, narrative skills) are not developmentally at the point that will readily support their transition to literacy (biologically a much more “unnatural” process than talking and listening). Few such children will have been fortunate enough to have their oral language difficulties identified prior to school entry, but at some point in the first one or two years of school, a significant proportion will be identified as having “learning difficulties” (or some variant of that label), because they are not achieving benchmarks with respect to early reading and writing skills. Is this likely to be a “new” problem that had no antecedents in the child’s earlier development? Maybe; in some cases. But in most cases, what is manifest at school is the surface representation (reading and writing problems) of an underlying but unidentified, language difficulty (or “impairment”, or “disorder”, or “deficit”…..that’s another whole debate!). 

So the notion of homotypic comorbidity asks us to apply Occam’s Razor in the process of classifying and organising children’s early language and literacy difficulties, and to employ the process of pattern recognition in thinking about children who struggle to cross the bridge to literacy. It reminds us that learning how to read is a linguistic task, so we need to think sequentially about what we are asking children to do with their emergent linguistic skills at different developmental stages. In the pre-school years, we ask the child to converse, tell and listen to stories, ask questions, sing songs, recite silly rhymes, follow instructions and so on. 

But on school entry, we are asking the child to shift their language use from talking and listening to now take in another symbolic code - reading and writing as well. That is not to say that written language is simply spoken language in the form of text. It is not. But if we didn’t know that a particular child had underlying language difficulties on school entry, s/he is likely to be labelled as having a “learning disorder” (or similar) in the early years of school. 

Failing to consider the developmental drivers of a successful transition to literacy poses serious threats, at two levels: (i) the application in early years classrooms of evidence-based direct instruction literacy teaching methods that focus on phonological and phonemic awareness, vocabulary, and comprehension, and (ii) the identification of children who need specialist services in the early years because of underlying language difficulties. 

So – parasitic relationships are not necessarily to be eschewed, they just need to be understood. Perhaps language and literacy might be better described as being “co-dependent best friends”.

Snowling, M, & Hume, C. (2012). Annual Research Review: The nature and classification of reading disorders. A commentary on proposals for DSM-5. The Journal of Child Psychology and Psychiatry, 53, 593-607.
 Caron, C., & Rutter, M. (1991). Comorbidity in child psychopathology: Concepts, issues and research strategies. Journal of Child Psychology and Psychiatry, 32, 1063–1080.

© Pamela Snow, 2014


  1. Hi Pamela,

    I keep coming back to this post. I use the term 'language is parasitic upon language' a lot since reading it'. Can I ask you about one dyslexic profile (I know it is along a continuum and often likely to be on the language continuum) where a student is very articulate, has a wide vocabulary yet cannot decode. For me, this would assume receptive and expression language is fine so work, rather than building on oral language, should concentrate on phonics. The reason I ask is that I often find these learners are put in interventions more likely to benefit those with a language impairment. It's the one profile (now discrepancy has been discredited as a reason for dyslexia) I struggle to fit with this term and current narrative which can also be 'dyslexia doesn't exist'. I'm really interested in how to support these learners and how to explain to schools such a 'pattern'.

    Thanks as always,


  2. Hi Jules
    Good to hear from you. I agree that the parasite metaphor is very compelling....except for the fact that someone pointed out to me that parasites ultimately destroy their hosts, which is not a pretty thought in relation to literacy gobbling up poor old language.

    However I think your question is best addressed through reference to the Simple View of Reading, which is central to the 2006 Rose Report. There's a lot of material about the SVR around on the web, and I'm including a link below that might be of use. Scroll down about half way to the 2x2 grid, with decoding on the x-axis and language comprehension on the y-axis. It sounds like the profile you're describing is siting in the top left quadrant and so needs extra support with decoding, phonological/phonemic awareness, sound-letter correspondences etc.

    Re the "dyslexia doesn't exist" narrative - I think it's more nuanced than that. Children with reading disorders exist, but as I saw someone point out today, we don't have one theory of reading for able readers and another for those who struggle. The problem (as I see it) with the term dyslexia is that it does not have one universal meaning and it is typically applied in situations where parents can afford expensive private assessments. Meanwhile everyone else just has a garden-variety reading problem.....but the interventions are the same, irrespective of the label. Go figure!

    I hope these few quick thoughts are of some use.