Cognitive risk factors for dyslexia and dyscalculia
Studies show that there are common risk factors for dyslexia and dyscalculia.
Are processing speed, time estimation and working memory common risk factors for the two disorders? These three abilities are known to be associated with attention deficit disorder. Because attention problems occur frequently with learning disabilities, they may be related to the specific learning disability.
Studies have found that in a third of children who have a certain learning disability (dyslexia / dyscalculia), the second disability will also be found. It has also been found that different areas of the brain are associated with each of the disabilities. It is accepted in the research literature that phonological processing and number processing are linked to dyslexia and dyscalculia respectively. Less is known about more general cognitive risk factors, such as processing speed, that may be common to both disorders, and may explain their comorbidities. A comorbidity of the two impairments for attention problems is known.
It is common to see phonological awareness as predictive of reading impairment. Processing speed may be the cause of both low phonological awareness and reading impairment. Also, processing speed was found to predict both dyslexia and attention problems.
One study showed an association between time estimation and ADHD, but not dyslexia, if the attention factor is controlled. The relationship between time estimation and dyscalculia has not yet been sufficiently investigated: there are several studies that have shown a link, but there is research on adults with dyscalculia who did not find a link when the test was not verbal (such as time reconstruction, where numbers should not be mentioned).
One study found a link between verbal memory and dyslexia. Studies examining the association between verbal memory and dyscalculia have yielded inconsistent findings.
A 2014 study by Moll K., Gobel S.M., Gooch D., Landerl K. & Snowling M.J. found that slow processing speed is a common risk factor for attention and dyslexia problems. In this study it was found that non-verbal processing speed (e.g., fast object naming) is related to attention. Verbal processing speed (e.g., fast naming of digits) is associated with both attention and dyslexia and is a risk factor for dyslexia even when the child has no attention problems.
The researchers also found that estimating time was associated with dyscalculia.
In addition, verbal memory has been found to be a risk factor for both dyslexia and dyscalculia. Support has also been found for previous findings showing a link between visual memory and dyscalculia.
The researchers did not find a unique common cause for the two disabilities (dyslexia and dyscalculia), but showed a profile that corresponds to the pattern of decrease observed in the specific groups (dyslexia / dyscalculia).
That is, the findings contradict the notion that combined disorder (dyslexia + dyscalculia) is a separate disorder (unique and different), and support its view as a pattern of the two specific disorders.
In conclusion, no common risk factors for the two disabilities (dyslexia and dyscalculia) were found in this study.