St Edward's Academic Review 2025

ACADEMIC REVIEW 2025

The biological theories of dyslexia

a clear image. Interestingly it has been demonstrated that in dyslexics, there is a magnocellular deficit which is compensated by a stronger parvocellular system, resulting in a lower ability to see larger and faster moving objects, but an improved ability to appreciate detail and colour. Dyslexics may therefore have an ability to acquire more detail from a source which is essential when translating an idea to a canvas, but they would struggle with constantly changing their visual frame when reading. It’s important to note that this theory is disputed, as not all individuals with a magnocellular deficit have dyslexia. However, most dyslexics do have a magnocellular deficit, suggesting it has a role to play. Research shows that dyslexia is multifactorial in nature, and many components of biology are involved. A key feature of dyslexia is a reduced ability to track lines of text whilst reading. Interestingly, Ward and Kapoula (2022) noted that dyslexic children frequently have challenged binocular vision. There can be many causes, but often it is related to a strabismus, or poor ocular neural connectivity. The resulting miscoordination of eye movement in these individuals can limit the ability to focus on the written word, causing tracking difficulties. These challenges can result in a difference in how an individual might perceive the world. Relating these observations to all dyslexics, the authors hypothesise that dyslexics constantly shift visual focus, which presents a challenge when reading, but allows dyslexics to absorb a greater range of stimuli. They also hypothesise that this facilitates a high level of connectivity between those stimuli, potentially resulting in enhanced artistic creativity. Their observations underline an important association between dyslexia and altered visual perception. Another biological difference in dyslexic brains relates to a ‘right brain skew.’ The two hemispheres of the brain have different roles in vision. The left hemisphere specialises in fine detail processing and carefully examines the fine detail of objects, whereas the right hemisphere specialises in processing the large scale, overall image and is especially effective in spotting connections that tie objects and ideas together. For example, the left brain is good at recognising a mouth, ears, or eyes, but the right brain is used to stitch those individual objects together to recognise a specific face (Eide & Eide, 2012). This ‘right brain skew’ was demonstrated by a group led by Shaywitz, Professor in Learning Development at Yale University, who used a technique called functional magnetic resonance

Dyslexia is a common condition found in children and adults which affects around 10% of the population, with 4% being severely affected (Bacon & Bennett, 2013). As a condition, dyslexia was first identified by Oswald Berkhan in 1881 and later named by Rudolf Berlin, an ophthalmologist, in 1887 (Chakravarty, 2009). Often thought of and written about as a learning disability, it is neurobiological in nature and manifests with overall deficits and speed deficits in lexical ability. It is also associated with poor auditory processing which adds a significant burden to acquiring and synthesising knowledge (Majeed, Hartanto, & Tan, 2021) (Taylor & Verstergaard, 2022). In 1968 the World Federation of Neurology defined dyslexia as, ‘A disorder in children (and adults) who despite conventional classroom experience fail to attain the language skills of reading, writing and spelling commensurate with their intellectual abilities’ (Taylor & Verstergaard, 2022). This is potentially an over-simplistic description of a complex condition, and one which may fail to assess whether the condition is accompanied by strengths in addition to challenges. Dyslexia is a multifactorial condition which manifests differently in every individual. Understanding the biological basis for dyslexia is important to assess how, in addition to certain challenges, it might be associated with specific benefits. There are several theories which potentially link dyslexia to creativity. The first hypothesises that there is a disequilibrium between the two main cell types involved in vision – the magnocellular and parvocellular neurones. These two cell types work together to coordinate the mechanics of vision when reading. If the eye accidentally moves the focus of vision off the fovea, then the magnocellular system helps correct the vision, moving the focus back to the fovea, restoring

‘ Dyslexia is a multifactorial condition which

manifests differently in every individual ’

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