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By Hiroko Tanaka, Ph.D., and Fumiko Hoeft, M.D., Ph.D.
May 2017
Clinical interest in dyslexia first arose from “unexpected” cases—where otherwise sufficiently intelligent individuals demonstrated problems with reading (Kussmaul, 1877). Dyslexia was thus originally defined as a significant discrepancy between reading ability and overall intellectual aptitude (often measured using an IQ test; for readability, from hereon referred to simply as IQ). Education law (Public Law 94-142) previously required such a discrepancy for the provision of special education services in schools.
Yet, in the past few decades, mounting evidence has shown that poor readers, regardless of their IQ, show similar difficulties in phonological processing and respond to reading intervention services equally well (Stuebing et al., 2009). Brain imaging has provided additional support;
brain activity during reading tasks looks similarly reduced for all poor readers, whether or not their IQ is discrepant from reading ability
Current federal law (the 2004 reauthorization of the Individuals with Disabilities Education Act [IDEA]) no longer requires a discrepancy to be present for special education eligibility. Definitions of dyslexia, including in the most recent Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5; American Psychiatric Association, 2013), have shifted away from requiring IQ-reading discrepancies in the identification of dyslexia and now include Response to Intervention (RTI) approaches for identification of the most severe poor readers. Indeed, a recent review argued that tests of cognitive ability (including IQ) are not necessary to identify dyslexia, and that reading tests alone should be sufficient (Fletcher & Miciak, 2016).
On the other hand, there are many children with very high IQ but with reading abilities within the average range—that is, their reading is “normal (age-appropriate)” but discrepantly lower than their IQ would predict. Some have called these children “gifted students with dyslexia,” and others have labeled them “average readers with high aptitude.” They also have been called “twice exceptional,” or “2e” students. In research, these children historically have been grouped into the category of “normal” readers as they are a minority population and had not shown any major differences compared to average readers without a discrepancy.
“Normal Readers” Who Struggle?
Are these children “struggling readers” who are prevented from reaching their full potential because of their discrepantly low reading ability? Or is their reading ability in fact adequate (i.e., their reading only appears weak due to their strengths in other domains)? Until recently, there has been no neurobiological evidence to support them as one or the other.
In a brain imaging study published recently, brain activation patterns in high-IQ children who had much lower (albeit “average—age-appropriate”) single-word reading ability were examined (Hancock, Gabrieli, & Hoeft, 2016). Remarkably, these children showed reduced brain activity in the same regions as readers with dyslexia—in findings from this study as well as in findings from earlier studies. Despite normal reading achievement, the brains of these children showed some of the same characteristics—left temporo-parietal dysfunction believed to be associated with phonological processing—as those of poor readers. These children showed less brain activation in these critical areas than both children with high IQ and high reading ability and children with normal IQ and normal reading ability. These children with high IQ and average reading ability demonstrated dysfunctional brain activation patterns—instead of an expected “IQ advantage” over normal readers with normal IQ.
The evidence provided in this research is consistent with the view that these children should be identified as having dyslexia because their brains are “dyslexia-like” with reduced brain activity in the same regions as other readers identified as having dyslexia. Still, since there is large individual variability within children with dyslexia, these results should be cautiously interpreted as initial evidence that requires further research to confirm.
Elliott and Grigorenko (2014) have argued in their book, The Dyslexia Debate, that “dyslexia” is becoming so broad and fragmented a term as to lose meaning. The IDA countered with an article (Malchow, 2014) noting that using the term “dyslexia” helps children not only to receive services and accommodations, but also to understand that their reading struggles are not their fault. It is easy to sympathize with this point. Typically, these average readers with high IQ are not identified as having dyslexia, and often do not qualify for accommodations or special education services as a result. As our brain imaging results suggest, since these children, as a group, show “dyslexic-like brains,” they, too, may benefit from accommodations and interventions.
Our study did not examine this question, which again requires further research. However, in cases where such students are clearly struggling to reach their academic potential because of reading challenges, it may be appropriate to provide intervention and/or accommodations. For example, extended time is an accommodation shown to help those with disabilities, though it is unlikely to be specific only to those with disabilities (Rogers, Lazarus, & Thurlow, 2016).
New Dimensional Paradigm
Psychiatric and medical research and practice are moving away from the binary (yes-no) categories of disorders and treatment, and are advancing into a new paradigm of identifying individuals based on dimensional classification (National Institute of Mental Health, n.d.) and personalized treatments (precision medicine; The White House, n.d.). In education and reading research, there are also strong proponents for these approaches, and RTI is one major step in that direction (For additional information that reflects the challenges in assessing the effectiveness of RTI, see Balu, 2015), but these efforts in education are only in their infancy.
An alternative way of interpreting the findings from Hancock et al. and other recent studies is that neuroscience may provide hope for developing new interventions for individuals with learning disorders. The current study shows that some children do reach average levels of reading achievement, despite apparent problems in the neurological basis for reading. If the mechanisms that enabled these children to reach typical reading achievement can be identified in future research, new interventions that facilitate these mechanisms might be developed to the great benefit of both discrepant and non-discrepant readers.
As neuroscience advances, it is becoming increasingly clear that dyslexia is not a single condition that is black and white, nor is there a single best option for remediation or accommodations. In the future, we may be able to create a complete picture of how different brain inefficiencies map to different aspects of reading deficiency (e.g., decoding vs. comprehension vs. fluency). This might enable individualized intervention and accommodations to maximize the benefit to children and to use financial resources most efficiently.
More Science of Dyslexia
December 2016
What Protective Factors Lead to Resilience in Dyslexia?
April 2016
Literacy and Dyslexia Revealed through Bilingual Brain Development
February 2016
What is the Role of the Visual System in Reading and Dyslexia?
June 2015
Summer Vacation: Important Insights for Reading Development
March 2015
Myths and Truths of Dyslexia in Different Writing Systems
December 2014
Many Layers of Dyslexia: Gene Discovery is Just Beginning
July 2014
Educational Neuroscience
REFERENCES
American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Arlington, VA: American Psychiatric Publishing.
Balu, R., Zhu, P., Doolittle, F., Schiller, E., Jenkins, J., & Gersten, R. (2015, November). Evaluation of response to intervention practices for elementary school reading.” Retrieved from https://ies.ed.gov/ncee/pubs/20164000/pdf/20164000.pdf
Elliott, J. G., & Grigorenko, E. L. (2014). The dyslexia debate. New York, NY: Cambridge University Press.
Fletcher, J. M. & Miciak, J. (2016) Comprehensive cognitive assessments are not necessary for the identification and treatment of learning disabilities. Archives of Clinical Neuropsychology. 1-6. doi: 10.1093/arclin/acw103
Hancock, R., Gabrieli, J. D. E., & Hoeft, F. (2016). Shared temporoparietal dysfunction in dyslexia and typical readers with discrepantly high IQ. Trends in Neuroscience and Education. 5(4), 173-177. doi: 10.1016/j.tine.2016.10.001
Kussmaul, A. (1877). Disturbance of speech. In von Ziemssen, H. W. (Ed.), Cyclopaedia of Practical Medicine, Volume XIV, (pp. 581-875). New York, New York: William Wood and Company.
Malchow, H. (2014, April). IDA responds to the “Dyslexia Debate.” Retrieved from https://dyslexiaida.wpengine.com/dyslexia-debate/
National Institute of Mental Health. (n.d.). Research domain criteria. Retrieved on January 12, 2017 from https://www.nimh.nih.gov/research-priorities/rdoc/index.shtml
Rogers, C. M., Lazarus, S. S., & Thurlow, M.L. (2016, May). A summary of research on the effects of test accommodations: 2013 – 2014 (NCEO Report 402). Retrieved from: https://nceo.umn.edu/docs/OnlinePubs/Report402/NCEOReport402.pdf
Simos, P. G., Rezaie, R., Papanicolaou, A. C., & Fletcher, J. M. (2013). Does IQ affect the functional brain network involved in pseudoword reading in students with reading disability? A magnetoencephalography study. Frontiers in Human Neuroscience, 7, 932. doi: 10.3389/fnhum.2013.00932
Stuebing, K. K., Barth, A. E., Molfese, P. J., Weiss, B., & Fletcher, J. M. (2009). IQ is not strongly related to response to reading instruction: A meta-analytic interpretation. Exceptional Children, 76(1), 31–51. doi: 10.1177/001440290907600102
Tanaka, H., Black, J. M., Hulme, C., Stanley, L. M., Kesler, S. R., Whitfield-Gabrieli, S., … Hoeft, F. (2011). The brain basis of the phonological deficit in dyslexia is independent of IQ. Psychological Science, 22(11), 1442–1451. doi: 10.1177/0956797611419521
The White House. (n.d.). The precision medicine initiative.Retrieved on January 12, 2017 from: https://www.whitehouse.gov/precision-medicine
Hiroko Tanaka, Ph.D., is a pediatric neuropsychologist. Her primary research has involved diagnostic models and risk factors for individuals with dyslexia. In her clinical work, she specializes in aiding and advocating for children with learning differences, neurodevelopmental disorders, and acquired brain injury. This includes using cognitive and psychoeducational tests to characterize a child’s cognitive profile of strengths and weaknesses, and to develop recommendations to enrich the educational and personal experience of children and their families.
Fumiko Hoeft, M.D., Ph.D., is Professor in the Department of Child & Adolescent Psychiatry and Weill Institute for Neurosciences (UCSF); Director of the Multi-UC-Campus Science-based Innovation in Learning Center (SILC) and UCSF Laboratory for Educational Neuroscience (brainLENS.org); and Research Scientist at Haskins Laboratories. She is a member of the UCSF Dyslexia Center Board, the IDA Board, the National Center for Learning Disabilities (NCLD) Scientific Advisory Board (SAB), and the Center for Childhood Creativity (CCC) SAB. She was the 2014 Geschwind Memorial Lecturer for IDA. BrainLENS is interested in how cognitive science can inform educational and clinical practices, with specific interests in understanding the neurobiological cause of dyslexia, early identification and prediction, and the emotional resilience necessary to succeed.
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