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Brain study reveals how much of math ability is genetic

It's a balance between nature and nurture.

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A bad relationship with math can start early, and anxiety or a lack of confidence around numbers can compound over time — transforming from a grade school phobia to a career hurdle.

But some math ability may not be shaped in the classroom. According to new research, some percentage of math ability might have deeper, biological roots.

Scientists in Germany argue that about one-fifth of math ability can be traced back to grey matter volume in the brain, influence by a gene, called ROBO1.

This gene is linked to the development of grey matter volume in the right parietal cortex, a region of the brain that’s involved in number representation. Patterns in grey matter volume were, in turn, positively associated with math test scores when children involved in the study reached second grade, their ages ranged from 7 to 9-years-old.

When the scientists initially measured the grey matter in the children's brains they were between the ages of 3 and 6-years-old and had not been formally trained in math. Because different variants of the ROBO1 gene influence grey matter volume, the authors propose that may have laid the groundwork for their math performance. They reasoned it was genetic variability's effect on grey matter that influenced whether or not a child was more skilled.

The paper was published Thursday in PLOS Biology.

Melissa Libertus is an associate professor at the University of Pittsburgh who studies learning and development. She says that the study is “compelling” and does appear to prove that there’s a chain of influence stretching from ROBO1 to math ability.

However, it’s not undeniable proof that one-fifth of differences in math abilities are definitely genetic.

“It is possible that we only see the associations between genes, brain volume, and math ability in the present study because the children tested here grew up in an environment that exposed them to mathematical concepts from a very young age,” she says.

The authors argue that a gene involved with grey matter volume may explain about 20 percent of differences in math ability.

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Are math skills genetic?

The study authors suggest that genetic influences, like ROBO1, actually “sculpt” the way the brain perceives numbers. Still, Libertus cautions it’s not just genes doing the sculpting.

Math instruction, even informally during early childhood, may prove to be the more important launching pad into a better understanding of math concepts.

Libertus adds that variations in pre-school children’s math abilities are influenced by how often parents or teachers talk about numbers or how often they engage in math-based activities like “playing board games that require counting, talking about money while shopping, or measuring and counting while cooking."

Those informal conversations about math could be at play in this study too.

This study was conducted in two samples of children: a 77-person “exploration sample” and a 101-person replication study. In both samples, the scientists collected grey matter measurements between 3 and 6-years-old (before math instruction) and then examined math test results when the children reached second grade.

Those two data collection periods are two snapshots in time. We don’t know what happened in the crucial period of early childhood between those two snapshots. Even if it’s not traditional math instruction, early childhood exposure to math concepts plays a big role in math performance later on.

Quantifying what happened between these two snapshots is outside the scope of this paper. But Libertus says it is “highly likely” that exposure to math at home and in other out of school settings may have been a factor, suggesting that genetics are part of a bigger puzzle.

Inheriting math ability – Scientists have long tried to tease apart how much of math ability is nature and how much is nurture.

On the genetic side, Libertus says that there is evidence that genetics may influence math ability. Genetic conditions like Williams syndrome, Fragile X syndrome, or Turner syndrome “are associated with poor math abilities,” she says.

"This leaves more than 80% of the variance in children’s math abilities unexplained."

She also points to dyscalculia, a math learning disability where children struggle to develop a basic sense of numbers. A 2001 study on 39 children with dyscalculia found that 66 percent of mothers, 40 percent of fathers, 53 percent of siblings, and 44 percent of second-degree relatives also had the condition.

There’s also evidence that intuitive “number sense” runs in families. In a 2017 study, Libertus found that parent’s scores on math tests could predict how well their children did on math exams in early childhood. But again, families also tend to share environments, so it’s not slam-dunk proof of the mathematical ability genetics.

As compelling as these studies are, the big picture is still unchanged. Math ability may have some genetic ties, it probably only explains a small fraction of that ability. Even in the current study, genes only explained 20 percent of math ability on its own.

“This leaves more than 80% of the variance in children’s math abilities unexplained,” Libertus says.

Abstract: Mathematical ability is heritable and related to several genes expressing proteins in the brain. It is unknown, however, which intermediate neural phenotypes could explain how these genes relate to mathematical ability. Here, we examined genetic effects on cerebral cortical volume of 3–6-year-old children without mathematical training to predict mathematical ability in school at 7–9 years of age. To this end, we followed an exploration sample (n = 101) and an independent replication sample (n = 77). We found that ROBO1, a gene known to regulate prenatal growth of cerebral cortical layers, is associated with the volume of the right parietal cortex, a key region for quantity representation. Individual volume differences in this region predicted up to a fifth of the behavioral variance in mathematical ability. Our findings indicate that a fundamental genetic component of the quantity processing system is rooted in the early development of the parietal cortex.

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