# 1.1 Biological explanations of dyslexia

Certain physical traits are often seen in people with reading difficulties, but their significance is still debated. These traits include being male and having subtle neurological and physical differences. Let’s delve into these aspects, and ask whether sex differences are fact or myth.

## Did you know?

People with dyslexia may have higher rates of allergies like asthma and eczema, as well as other autoimmune disorders. This is possibly caused by the KIAA0319 gene (Dyslexia Research Trust, 2020). While this might seem unrelated to dyslexia, factors like these provide insights into the biological causes when linked to behavioural symptoms.

An intriguing aspect of dyslexia is the apparent excess of males who are affected. Historical medical journals reported over a century ago about ‘gifted boys’ who suffered from ‘word blindness’ (Helland, 2020, p. 1).

If it’s something you’ve heard about or considered before, what do you think: are boys/males more affected by dyslexia than girls/women?

Early neuroimaging studies suggested that boys are more often diagnosed with dyslexia than girls. This may be due to several factors:

- In the past, society’s expectations of boys and girls were very different with respect to educational achievement.
- Girls tend to hide their difficulties while boys perhaps are more likely to ‘externalise’ their frustrations.
- Research and samples have been male-dominated.

This reflects a referral bias, where boys are more often identified as dyslexic than girls (Krafnick and Evans, 2019). Even when equal gender sample sizes are now used, the interpretation framework continues to depend on theories derived from and composed of males.

Despite evidence showing no gender difference in the heritability of reading difficulties (Wadsworth, Knopik and DeFries, 2000), recognising any other potential gender differences is crucial. This could change our understanding of behaviour, brain anatomy, and activity in both typical and atypical development. The apparent sex difference still lacks adequate explanation, highlighting the need for more inclusive research.

## Behavioural differences

Differentiation between sexes seems to be clearer when exploring behavioural differences (Krafnick and Evans, 2019). Girls display particular strength in domain-general skills, e.g. working memory and visuospatial, and domain-specific skills, e.g. verbal conceptualisation and orthographic coding. Boys display particular strength in verbal reasoning abilities.

Scholars believe more research is needed on sex differentiation. Kraftnick and Evans note growing interest in how sex differences impact disorders, though it’s not universally accepted (2019, p. 3).

Let’s check out what the last decade or so of evidence demonstrates, in order to identify and assess any biological explanations.

OpenLearn - Understanding dyslexia
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