Decoupling IQ from Dyslexia
Dyslexia or a Specific Learning Disability is seen in children when they show a significant difficulty with the speed and accuracy with which they decode words in the text and they are reading.
Mostly, we find that comprehension of text and the spelling ability of the child are also affected.
The dyslexia Association of India™ is seeing a lot of reports where a simple IQ test has been used to diagnose a child as being dyslexic.
How accurate is this procedure is a very controversial issue, and it is our equivocal belief that a simple I.Q test is just is not sufficient to categorize a child - to have dyslexia.
While measuring IQ - is an important factor to assess the general conceptual ability of the child, the validity of identifying a child - with a learning disability on the basis of a discrepancy, between his IQ and academic achievement - is very simplistic and parents should question this norm - as there are different dimensions which are associated with learning disabilities that come bundled with each individual child and which need a through meta-analysis before ‘labeling’ any child.
Labeling - for identifying a child with learning disorder, is not ‘wrong’, as it enables the child to obtain targeted and specific remediation. But the role of IQ, in predicting prognosis and intervention response is once again very simplistic, as academic and cognitive skills are not the only dimensions in which IQ variance in a academically low achieving child may differ from a high achieving child.
A high measured IQ, may be associated with better prognosis and vice versa, but IQ or IQ – discrepancy is not solely associated with better reading outcomes.
A significant number of professionals feel that capacity limits content, and that if a child on the measured Scale of intelligence is on the lower end, then how can this particular child with his measured lower cognitive capacity strive for educational attainment where he can rise higher than his measured educable capacity.
What we forget is that intelligence tests measure skills that are taught in schools, such as vocabulary and mathematics, which facilitate critical reasoning. They do not measure skills like phonological awareness, segmenting, decoding, rapid naming to name a few and normally children who show reading problems have issues with these aspects of learning to read.
We would also like to point out that IQ is not helpful in performing an academic test, even though it might help a child acquire the academic knowledge being assessed in that particular test.
In fact now we are of the firm conclusion that IQ is largely irrelevant to the definition of Learning Disabilities and even in the United States regulations have been modified so that IQ tests are not be mandated for Learning disabilities identification as IQ is not a proxy for learning potential.
The rationale for suggesting that IQ directly influences the attainment of academic and/or language skills, has its limitations and the psychometric significance of IQ –attainment difference scores, and simple comparisons of IQ and attainment measures is incorrect. In fact when we compare cognitive functions in children with reading disabilities we find only small effect size differences between poorer readers relative to discrepant and nondiscrepant IQ scores.
IQ is itself influenced by many schooling differences. Reduced word and print exposure in poor children or children who cannot read produces lowered IQ and learning over time - and the influence of gene and environment is bidirectional - in that the same developmental disadvantage that is part of many neurodevelopmental disorders - lowers both IQ and academic skills.
The cognitive difficulties of a child with dyslexia may include problems with speech perception, language memory, manipulating the basic sounds in a language and learning the sounds of letters. Dyslexia is actually a neurological condition, probably with a genetic base and it is also accepted that this specific learning disability runs in families.
Extensive research has identified several chromosomes that appear to contain the gene or genes for dyslexia, although the exact genetic mechanism is not known and the inheritance patterns are yet not fully known. Environmental factors do play a role, but the influence of genetics is now accepted to be quite strong in dyslexia.
Differences in the way the brain is wired, along with electrophysiological and structural characteristics of the brain of a dyslexic child make it very important that simplistic assessments do not form the basis of any response to intervention and immediate categorization of the child as having dyslexia.
Even amongst children, who are assessed to have dyslexia, phonological dyslexics are considered to be more genetically influenced, whereas dyslexic children who have trouble reading exception words indicate for considerable less heritable components. What this means is, that no two children are the same and we have to be very careful before reaching a conclusion on the diagnosis.
It may come across as a bit gross, for parents, but the neurological basis for this specific learning difference points towards an absence of the usual asymmetry in the Plannum Temporale. Scientists have also discovered structural differences between a normal child’s and a dyslexic child’s brain where the Corpus Callosum, which controls the communication between the two hemispheres of the brain not performing at optimum levels.
Electrophysiological studies have also shown event related potentials of dyslexic brains, in contrast to non-dyslexic brains - failing to show what is called mismatched negativity, which is negative deflection - in the wave response to a change in stimulus. Further fMRI studies have helped us learn about abnormalities in the left hemisphere of a dyslexic brain, specifically the extrapyramidical & limbic systems, amygdala, hippocampus, para-hippocampus gyrus, putamen and globus 'spallidus.
If this is so, then the categorization of children – involving the discrepancy between an IQ score and reading score is incorrect. What we are generally seeing is that if IQ > reading score or if - when inversely IQ < reading score, the assessing professional is giving a label of dyslexia to the child. This is not correct. This IQ definition should be discredited, as IQ measures vocabulary, verbal memory and specific knowledge as we have mentioned - and normally we do not find any difference in children who have a reading problem and those children who have a discrepancy between their IQ scores and reading scores - and those children who do not.
A discrepant IQ does not necessarily indicate dyslexia, and maybe a low score on a reading test may in fact be an indication of a reading problem rather than an innate cognitive and / or an Intelligence problem. The question that then arises is – are we looking in the correct place for the correct answers, or are we oversimplifying the entire issue and assuming that the ‘Mathew Affect’ - where children who start out at low levels of a variable like ‘learning to read’ fall even further behind over a period of time and as the gap widens - and we simply are making a quick assessment of the specific learning disorder by measuring acquired cognitive gains?
IQ and measurement of General Conceptual Ability are very important. They however should be a part of the whole assessment process and viewed in a holistic manner. We have to be cautious because, children who are latter identified to be dyslexic, learn to read very arduously and as the process of reading is very difficult for them, they tend to read less over a period of time as compared to typical readers and consequently acquire lower levels of vocabulary and general world knowledge that comes from reading text. In this context for a child with Dyslexia, his intellectual development may actually depend more on environmental inputs than academic and ‘out of school’ text reading. With this, reading for a child with Dyslexia would have a weaker relation to changes in IQ than it would for a child who is not Dyslexic and the Dyslexic child’s developing intelligence would seek stimulation in domains other than reading.
For a Non-Dyslexic child there is a positive reciprocal feedback loop, but for a Dyslexic child, there would be a disconnection over time between his IQ and reading ability. This child’s IQ may be high and when measured would be visible in his higher levels of fluid IQ, but the mechanism for the close coupling of his overall cognitive and reading development over time to the crystallized IQ would be disjointed due to the deficit of ‘reading to learn’ that is not occurring.
In these situations, a simple measurement of a child’s Intelligence Quotient by whichever test or assessment by a professional would in all certainty lead to a misdiagnosis of a ‘Specific Learning Disability’.
India is a country where the reality of Socio Economic Disparities looms large in our day-to-day lives and the impact this can have on children from diverse backgrounds can be significant.
If any professional were to use the measured IQ to define a child as having Dyslexia, it may represent an incorrect measure of the child’s problems. What we need to appreciate is that - two children who have equivalent reading difficulties - but come from the opposite segments of the Economic Divide might get diagnosed differently by the use of the IQ – attainment discrepancy criterion, as the child from a socially weaker section of society (SWS) is more likely to be classified as a poor reader or in the context of simple IQ measures as a Dyslexic.
Once again why?
When we measure the IQ for a child - we are measuring factual knowledge, expressive language abilities, and short-term memory, among other skills, and because children with learning disabilities have deficits in these areas, their scores may be spuriously low. In addition, some children with low IQ scores can be good readers, which indicates that low IQ scores do not necessarily result in poor reading. In fact poor readers at a variety of IQ levels tend to show similar reading, spelling, language, and memory deficits. Therefore on logical and empirical grounds, IQ test scores may not be necessary for defining a child as having a Specific Learning Disability or Dyslexia and this historical reification of general intelligence or IQ as a causal construct that measures aptitude and potential rather than achievement and performance should not become the platform for the idea that IQ has a special status analyzing neurocognitive functions in neurodevelopmental disorders.
The Dyslexia Association of India™ would like to make a case for a broader and more deep assessment of children before classifying them with a particular Learning Difference such as ‘Dyslexia’ as even if IQ accounted for all the variability in performance on a cognitive task for children, it is impossible to distinguish between IQ as a cause, IQ as an outcome, or as a spurious associate between (itself) IQ and the cognitive measure we are trying to test for the child - in which case any professional should first have to identify what the common latent variable is in relation to the expected learning disorder and its relation to both IQ and the cognitive measure being attempted to be assessed.
There is a serious question on the explanatory power of IQ for attempting diagnosis of Neurodevelopmental Disorders, and if professionals are not interpreting the relation of IQ and the specific dependent variable accurately, the construct validity of assessing a neurodevelopmental disorder just by assessing the IQ of the child and is fraught with danger.
When faced with IQ scores parents and children have to appreciate that as a product of multiple influences, the IQ score they are reading for their child or for themselves, is a volatile, index of global functional outcome: the final common path of the child’s genetic, biological, neural, cognitive, educational, and experiential life. At best the IQ scores provide a general index of the representativeness of a sample, which facilitates comparisons of global outcomes across neurodevelopmental disorders.
The views expressed here are equivocal and the form an opinion that is private and personal to the thinking within the Dyslexia Association of India™. It is not meant to challenge any work, substitute any research or question what other academics and researchers may be doing in similar fields.
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