Here is more information/critiques of the Magnocellular Theory of Dyslexia. The bottom line is that this visual phenomenon does not explain dyslexia.
- Statement from the American Academy of Ophthalmology
- American Academy of Pediatrics on vision therapy for learning disabilities and dyslexia:
International Dyslexia Association posted this information on vision therapy as it pertains to treatment for struggling readers. As you will see, vision therapy is not recommended for the treatment of weak reading skills.
- Ramus (2003): Only a portion of individuals with dyslexia demonstrate visual processing deficits and causal links are suspect (see Olulade et al., below)
- This and other visual-processing deficit hypotheses, such as scotopic sensitivity/Irlen syndrome, are often based on difficulties in reading text (i.e., notions that text appears jumbled, crowded, or jittery), when a fundamental problem with dyslexia is difficulty reading individual words
- Skoyles & Skottun (2004): Magnocellular deficits do not discriminate individuals with dyslexia from those without (many individuals with magnocellular deficits do not have dyslexia)
- Skottun & Skoyles (2008):
- Similar perceptual difficulties observed in autism, Williams’s syndrome, hemiplegia, and schizophrenia
- Many tools are poorly suited for measuring dynamic aspects of vision; little evidence for a temporal visual deficit in dyslexia.
- Olulade, Napolielo, & Eden (2013): “Our results provide strong evidence that visual magnocellular dysfunction is not causal to dyslexia but may instead be consequential to impoverished reading.”
- Paulesu et al. (2014) meta-analysis of PET and fMRI activation studies: “…we could not find evidence for the visual/magnocellular hypothesis of dyslexia, if this was to be benchmarked by a reduced recruitment of area V5/MT (Eden et al., 1996)”
- Edwards & Schatschneider (2020): “Results showed that in a sample of 83 college students magnocellular performance was not significantly correlated with a reading rate or rapid letter naming…This provides evidence against the idea that having low magnocellular performance will result in poor reading ability.”
Edwards, A. A., & Schatschneider, C. (2020). Magnocellular pathway and reading rate: An equivalence test analysis. Scientific Studies of Reading, 24(3), 264-273.
Olulade, O. A., Napoliello, E. M., & Eden, G. F. (2013). Abnormal visual motion processing is not a cause of dyslexia. Neuron, 79(1), 180-190.
Paulesu, E., Danelli, L., & Berlingeri, M. (2014). Reading the dyslexic brain: multiple dysfunctional routes revealed by a new meta-analysis of PET and fMRI activation studies. Frontiers in Human Neuroscience, 8, 1-20.
Ramus, F. (2003). Developmental dyslexia: Specific phonological deficit or general sensorimotor dysfunction? Current Opinion in Neurobiology, 13(2), 212-218.
Skottun, B. C., & Skoyles, J. R. (2008). Coherent motion, magnocellular sensitivity and the causation of dyslexia. International Journal of Neuroscience, 118(1), 185-190.
Skoyles, J., & Skottun, B. C. (2004). On the prevalence of magnocellular deficits in the visual system of non-dyslexic individuals. Brain and Language, 88(1), 79-82.