Dyscalculia – Part IV: Heritability and the effects of brain damage on numerical abilities
If identical twins are found to be sufficiently more concordant than fraternal twins, then there is a significant contribution of genetic factors.
By 전승혜 Seonghae Jeon, M.P.A.
Before we come up with implementation methods through which we can utilize to effectively intervene the learning process of dyscalculic children, we should know what actually causes this condition to occur.
It is well-known that there is a specific genetic effect on standardized test of math and that school performance on all the measures is affected by shared environment for the effects of domain-general cognitive abilities. However, there is very little evidence that dyscalculia is inherited or unchanging, and for most people, it is congenital; they are born with the condition.
To find evidence that dyscalculia may be inherited, psychologists and researchers conducted studies on twins by comparing the variance in the concordance of identical twins and fraternal twins to get an estimate of heritability. The assumption was, if the concordance is the same between the two groups of twins, then there is little or no contribution of heritability; if identical twins are found to be sufficiently more concordant than fraternal twins, then there is a significant contribution of genetic factors.
Through multiple studies over several decades, they concluded that there was a moderate to significant level of genetic influence on children’s mathematical ability along with their reading and linguistic abilities and IQ. They also stressed that a highly correlated factor called “generalist genes” affect all aspects of cognitive ability and disability and that non-shared, environmental influences operate as specialists and contribute to being bad at math.
In summary, continuity is genetic and change is environmental: age-to-age stability is primarily mediated genetically, whereas the environment contributes to change from age to age.
Other studies show that arithmetical impairments and core deficits have been observed in many genetic conditions, including but not limited to, Turner’s Syndrome, Cerebral Palsy, and Williams Syndrome.
Children born very preterm ( more than 32 weeks) or extremely preterm ( less than 26 weeks) or with very low birth weight ( less than 1.5kg) are likely to show poorer academic performance at school especially at math and there appears to be a domain-specific deficit. Though there is no direct, cause-and-effect relationship between such birth conditions and incidence of dyscalculia, we may conclude that disturbance to pregnancy can lead to dyscalculia.
We must keep in mind that simply being bad at math is not a symptom of dyscalculia. Knowing that more research needs to be done to learn what causes dyscalculia to occur, how can we diagnose a child with dyscalculia and on what base?
Butterworth, B., (2018). Science of Dyscalculia. 1st ed. Routledge. https://doi.org/10.4324/9781315538112