It is estimated that Dyscalculia, the maths disorder or disability, is present in about 7% of school children.
It is possible that Dyscalculia simply represents a component of a more general learning disability.
If this is true, there should be a large overlap between Dyscalculia and other learning disorders, such as Dyslexia, the reading disorder.
Donald Compton and colleagues at Vanderbilt University is information in addressing this issue.
They completed a longitudinal study of 684 students from 3rd grade through the 5th grade assessing four academic achievement domains:
- reading comprehension
- word reading
- applied math problems
- math calculation skills
Additionally, they examined five student cognitive skills including: non-verbal problem solving, processing speed, concept formation, language and working memory.
The key finding from their study is that Dyscalculia in general terms, appears to be a specific disorder.
Although 3.8% of their school children sample had both Dyslexia (reading disorder) and Dyscalculia (math /calculations disorder), 10.1% were estimated to have only Dyscalculia and 6.6% were estimated to have only Dyslexia.
They noted their "results indicate that, although co-morbidity (the co-existance of Dyslexia and Dyscalculia together in one person) does occur, it is limited to approximately 20% of student with learning disability. This adds credence to the notion that reading and mathematics learning disability may be distinct and separate".
Differences between Dyscalculia and Dyslexia included the following:
- Boys had higher rates of Dyslexia, reading comprehension learning disability, while Dyscalculia (math problem and calculation types) were found equally in boy and girl students
- Both Dyscalculia and Dyslexia rates were linked to student poverty status-students in the lowest socio-economic group had higher rates of both math and reading disorders.
- Both Dyscalculia and Dyslexia students showed relative strength in the processing speed cognitive domain
This study lends support to Dyscalculia being a specific type of learning disability that often occurs without Dyslexia as a co-occurring reading disorder.
Dyscalculia appears to be the most common learning disability in girl students.
Compton DL, Fuchs LS, Fuchs D, Lambert W, & Hamlett C (2012). The cognitive and academic profiles of reading and mathematics learning disabilities. Journal of learning disabilities, 45 (1), 79-95 PMID: 21444929