New results from an UK Twin study: genes are more than an influence on intelligence

Last year I discussed a twin study on 11000 twins in the UK showing the effect genetics have an test results in school. Now there is a new study on 13000 twins in the UK published on PLOSOne. The title makes it already clear: “The high heritability of educational achievement reflects many genetically influenced traits, not just intelligence” (and do note that even intelligence still is influenced by environment too to a great extent).

Let’s examine the abstract:

Because educational achievement at the end of compulsory schooling represents a major tipping point in life, understanding its causes and correlates is important for individual children, their families, and society. Here we identify the general ingredients of educational achievement using a multivariate design that goes beyond intelligence to consider a wide range of predictors, such as self-efficacy, personality, and behavior problems, to assess their independent and joint contributions to educational achievement. We use a genetically sensitive design to address the question of why educational achievement is so highly heritable. We focus on the results of a United Kingdom-wide examination, the General Certificate of Secondary Education (GCSE), which is administered at the end of compulsory education at age 16. GCSE scores were obtained for 13,306 twins at age 16, whom we also assessed contemporaneously on 83 scales that were condensed to nine broad psychological domains, including intelligence, self-efficacy, personality, well-being, and behavior problems. The mean of GCSE core subjects (English, mathematics, science) is more heritable (62%) than the nine predictor domains (35–58%). Each of the domains correlates significantly with GCSE results, and these correlations are largely mediated genetically. The main finding is that, although intelligence accounts for more of the heritability of GCSE than any other single domain, the other domains collectively account for about as much GCSE heritability as intelligence. Together with intelligence, these domains account for 75% of the heritability of GCSE. We conclude that the high heritability of educational achievement reflects many genetically influenced traits, not just intelligence.

Wait a minute. In the first study we discussed an average of 58%, but now we’re talking about 75%? When looking at the actual conclusion it’s a bit more complicated but still depressing:

“We found that, although intelligence accounts for more of the heritability of educational achievement at age 16 than any of the other domains, the other domains collectively accounted for about as much GCSE heritability as intelligence. Collectively, all cognitive and noncognitive predictors accounted for 75% of the heritability of GCSE. These genetic results turn some fundamental assumptions about education upside down. For example, one of the reasons that the contribution of intelligence is sometimes considered controversial when discussing educational outcomes is that intelligence is viewed as genetic, whereas achievement is thought to be due to environmentally driven influences from home and school. In addition, other behavioral traits such as self-efficacy are presumed to contribute to educational achievement for envi- ronmental reasons. However, our results suggest the opposite: Genetic influence is greater for achievement than for intelligence, and other behavioral traits are related to educational achievement largely for genetic reasons.”

Luckily the researchers have a consolation in the end (bold by me):

“It is important to emphasize that finding genetic influence is not a counsel of despair in terms of helping children who find learning difficult—heritability does not imply immutability. Heritability describes the extent to which phenotypic variance can be ascribed to DNA differences, on average, in a particular population at a particular time. In other words, heritability describes what is; it does not predict what could be. For example, despite high heritability, with sufficient educational effort, nearly all children could reach minimal levels of literacy and numeracy, which is an explicit goal of education in Finland. Success in achieving that goal would reduce phenotypic variance, which could change heritability. Another example is greater equality of opportunity in education would decrease environmental sources of variance and thus increase heritability, which has been demonstrated empirically.”

And what does this mean for policy-makers?

“No policy implications necessarily follow from finding that genetics permeates educational achievement, because policy depends on values and knowledge. However, it is to be hoped that better policy decisions can be made with knowledge of genetic influence rather than assuming that all differences are environmental in origin.”

Do read also this piece on The Conversation by one of the researchers in which he pleas for more personalized learning.


2 thoughts on “New results from an UK Twin study: genes are more than an influence on intelligence

  1. The study’s “genetic reasons” term doesn’t mean that the researchers actually took genetic samples. From one news article: “Identical twins share 100 percent of their genes while non-identical twins share just 50 percent of their genes. Because these sets of twins share the same environment, the scientists were able to compare identical and non-identical twins to estimate the relative contributions of genetic and environmental factors.”

    This estimating method produced an artificial divide between genetic and environmental factors. Identical twins start out sharing 100% of their genes, but then their genes become expressed differently – often because of environmental factors – to produce unique individuals even before birth. The sets of identical twins were definitely not the 100% same genetic makeup between themselves at age 16 as they were at conception, and that assumption was the foundation of the estimating method.

    I feel that the researchers didn’t prove their case that “genetic reasons” were a causal factor to the stated extent. Although their estimating method’s numbers may have indicated that the above exercise was valid, that didn’t necessarily mean that the method’s results reflected the reality of genetic and epigenetic influences on the subjects. Better methods of estimating “the relative contributions of genetic and environmental factors” are available with genetic sampling.

    The funniest thing I saw in the study’s news coverage was one where someone argued that the researchers were wrong and that they needed educational psychologists on their staff to interpret the data. Guess the profession of the arguer!

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