Title: Literacy and Numeracy Are More Heritable Than Intelligence in Primary School
Because literacy and numeracy are the focus of teaching in schools, whereas general cognitive ability (g, intelligence) is not, it would be reasonable to expect that literacy and numeracy are less heritable than g. Here, we directly compare heritabilities of multiple measures of literacy, numeracy, and g in a United Kingdom sample of 7,500 pairs of twins assessed longitudinally at ages 7, 9, and 12. We show that differences between children are significantly and substantially more heritable for literacy and numeracy than for g at ages 7 and 9, but not 12. We suggest that the reason for this counterintuitive result is that universal education in the early school years reduces environmental disparities so that individual differences that remain are to a greater extent due to genetic differences. In contrast, the heritability of g increases during development as individuals select and create their own environments correlated with their genetic propensities.The paper is available for free at the same page.
Another reason for thinking that literacy and numeracy are less heritable than g is that literacy and numeracy are relatively recent human inventions, whereas the abstract reasoning and problem solving central to g seem to be key to human evolution.I've previously proffered my opinion that if "g" was key to human evolution, then the variability of whatever genes caused/correlated with "g" would be subject to strong selection, and "g" would be less heritable, not more.
The policy hook:
Regardless of the causes of the high heritability of literacy and numeracy, finding that two thirds of the total variance in these taught skills can be attributed to genetic differences between children highlights the need to incorporate genetics into educational policy.Just how do we follow this policy prescription?
PS: what Plomin, one of the co-authors of the paper, thinks is rather clear.
Let us not hear any apologia for him.
‘There’s this slightly misleading fact,’ says Plomin, ‘that kids’ cognitive abilities is related to the number of books in the house. And it’s true that kids who grow up in houses with books are smarter. But that’s not why they’re smarter!
‘Sometimes, if you talk to teachers they behave as if it’s books themselves that cause the cognitive development of kids. They say: “See? Books don’t have DNA!” But they don’t consider that the fact that there are books in the house is because the parents are smart and like to read! Oh, it makes me feel as if I’m in Alice in Wonderland!’