Is 25 years a long or a short time in research? Can I still stand by what I said then? I am so used to finding published papers by a simple web search, including my own. So I was surprised when I found no weblink when I tried to tweet about a paper that appeared in 1995 in the Journal of Educational and Child Psychology published by the British Psychological Society. However I found another later paper (2001) also with some images that I wanted to refer to. They form a schematic framework that I developed with John Morton, to help explain neuro-developmental disorders. The story for dyslexia should tell itself if the schematics work at all. However, I will include a few explanations and excerpts from the old paper.
The framework allows us to make a distinction between children who are ‘poor readers’ and those who are ‘dyslexic’. 25 years ago a big question mark hung over this distinction. Dyslexia was identified as a reading problem. So why not stick with a behavioural description of poor reading , objectively measurable by standard reading tests? Why stigmatise child with a mystery condition? Many teachers and researchers felt this was the right approach. However, I was not convinced. The framework shows that a distinction can be made at the cognitive and biological levels. This means, you can be a poor reader and not dyslexic, if you did not have any proper teaching. On the other hand, you can be a good reader and dyslexic, – if you had a gifted teacher.
So what is there at the cognitive level that defines dyslexia? Still my favourite explanation is that there is a problem with phonology. Although phonology still remains underspecified, it is now widely endorsed as a core deficit in dyslexia. Maggie Snowling was one of the pioneers developing this idea, and her book ‘Dyslexia’ remains a classic.
Phonology is a concept that belongs to the cognitive level of description. It is a crucial ability for learning the alphabetic principle, where bits of speech sound have to be matched to visual sympols, even though these bits don’t have an objective physical existence. They are natural entities only to those of us who have learned to use the alphabet. Phonology is a cognitive ability that existed well before the alphabet was invented. I imagine it as a gadget prewired in the brain that enables us to process and to produce speech at a fast pace. It allows us to effortlessly segment the stream of speech so that segments can be mapped to letters, syllables and words. Sometimes these segments can get cut off, which gives us the tip of the tongue phenomenon, and sometimes they can be mixed up, which gives us involuntary errors such as spoonerisms. When did I start to believe that phonology is a thing? Perhaps it started long ago when I did some in depth case studies. There were highly able children who had poor phonology and there were not so able children who had relatively good phonology. This kind of dissociation suggests that phonology is a separate cognitive component, which can be faulty in some cases.
In principle there could be problems in additional components as well. For example, problems in attention would also affect how well a child learns to read. An attention deficit might result in poor learning in formal school settings, and hence, in result in poor achievements in a whole range of school subjects, including reading. If there was an additional phonological deficit, then this would aggravate the problem.Phonology would be a nebulous concept if there were not a number of behavioural tests that are able to tap it. They are far from ‘pure’, because other factors, such as general ability, attention and motivation, all contribute to test performance,. Hence clinical judgement is always needed to interpret test scores. Still, batteries of phonological tests have proved their worth and are widely used in clinical and educational assessments.
Phonology has a basis in the brain. There are now a large number of brain imaging studies to demonstrate this. Ours was one of the first, and it used PET scans. The study tentatively suggested that dyslexic brains showed a disconnection between the language and speech areas of the brain. Interestingly, a recent longitudinal study also suggests a lack of effective brain connectivity in dyslexic readers. The best overview of the brain regions involved in reading and in different aspects of speech and language can be found in the book Reading in the Brain by Stan Dehaene. Dehaene explores some intriguing hypotheses about the way the brain has adapted itself to processing written language.
Here are some more of my speculations from 25 years ago. Dyslexia tells us not only that there is a phonology gadget in the brain but it also tells us what happens if it fails. Some effects can be captured by simple tests as summarised in the figure. Other effects are more insidious. For example, dyslexic children learn words at a slower pace. This means that dyslexic children are doing less well on vocabulary tests compared with same age peers.
But what is the fault at the brain level that causes a phonological problem? I was proud to lead a group investigating this question in three different European languages. We found a subtle fault in left temporal cortex, pointing to a disconnection between speech processing areas. Later, Eraldo Paulesu went on to ask why should there be this fault at this particular place. Were there anatomical abnormalities in brain structure? Indeed there were. Speculatively, there could have been problems in brain development well before birth. One classic idea, first proposed in the 1970s, is that the anatomical abnormalities are instances of a neuronal migration disorder. During development, cells migrate into their destined layers in the cortex. This is an amazingly complex process and a complex genetic programme is needed for this. It is not surprising that sometimes glitches occur. The hypothesis that cell migration failures affect specific brain areas and result in specific cognitive deficits was further developed by Franck Ramus in a theoretical paper. I was gratified to see that he used the Frith-Morton framework to explore this idea.
So what can be done to help dyslexic children if they have a problem in a brain system that underpins phonology? Even if nothing can be done at the brain level, plenty can be done at the cognitive and behavioural levels. Learning to read can be done via different strategies. If reading via the normal grapheme-phoneme strategy is not possible, you can use cues to the meaning from the sentence and text, and usually you can get at least the beginning sound of a word. Guessing from context seems to be important for dyslexics and should not be discouraged. Likewise, they should not be forced to read aloud. Spell checkers are a boon. Ideally, learn to read in Italian! In a very transparent writing system, such as Italian, learning to read almost fool proof. In a comparison of English and Italian readers we showed that Italian readers were more accurate and faster than English readers. If the Italian writing system is a therapy for dyslexia, the English writing system is a magnifying glass that makes dyslexia very visible.