Nature and nurture in education

What is heritability and what does it have to do with education?
skeeze, Pixabay.com, CC0 1.0
skeeze, Pixabay.com, CC0 1.0

Recent studies investigating the relative roles of nature and nurture in education have provoked much debate. This debate is partly fuelled by a misunderstanding, or miscommunication, of the term ‘heritability’ and its scientific meaning. Getting to grips with key scientific terms will help to move the debate forward and encourage productive engagement between education and science.

Research is making great strides in uncovering the role of genes in educational outcomes. With the arrival of more research it is essential that non-scientists, including educators, parents, and policymakers, understand what the terminology means so that they can meaningfully engage in debate.

At present, considered debate about how to improve educational outcomes, particularly for low performers, can be hindered if we don’t accept scientific findings that appear to contradict our values or intuition. In part this is due to misunderstandings of scientific terms, and one term that has a particular tendency to be counterintuitive, and has caused much confusion and debate, is heritability.

For a given trait or educational outcome, heritability describes the proportion of variation in the population that is accounted for by genes. To take an example, GCSE (General Certificate of Secondary Education; the tests taken at age 16 in the UK) results were estimated to be 62% heritable. This is sometimes incorrectly taken to mean that 62% of an individual’s GCSE result is explained by their genes. What it actually means is that 62% of the differences in GCSE results between members of the population is explained by genes.

Heritability estimates depend on the environment. If the environment is very similar for everyone, then heritability of a trait is likely to be higher, since individual differences in the trait can’t be explained by different environments. In contrast, if environments are very different for different members of a population, then the heritability estimate is likely to be lower, since different environments will explain more of the variation.

As a result, heritability estimates can differ between countries due to different environments. For example, a country with a very standardised school system might have much higher estimates of heritability compared to a country where schools vary widely.

“In addition to changing depending on the environment, heritability estimates also change with age.”

A very high heritability estimate, therefore, does not mean that the environment does not matter, it just means that in this specific population, genes explain more of the variation. For GCSE grades in the UK then, the fairly high estimate of 62% heritability should not be taken to mean that schools provide little value; rather it may suggest that UK schools are providing similar learning environments.

In addition, a heritability estimate does not tell us which specific genes are associated with the differences we see. It therefore cannot tell us how much of an impact an individual gene has, or the mechanism through which the genes are having an effect. Studies are now starting to investigate specific genes, and the evidence is showing that many genes have an impact on traits and educational outcomes, with each one of these genes having a very small impact.

In addition to changing depending on the environment, heritability estimates also change with age. Heritability estimates tend to increase with age, such that more variance is explained by genes than environment as we get older. One estimate is that genes explain 41% of the variability in intelligence in children, but 66% of the variation in intelligence in young adults.

“Schools and teachers have a crucial impact on students’ learning, and high heritability likely reflects the fact that all students sampled are exposed to high quality learning environments.”

This is a counterintuitive idea since we might expect that as we have more experiences we get further from any genetic influences. But to the contrary, heritability is thought to increase because we have more choice over our experiences as we get older, choosing to engage in activities that suit our genetic propensities.

Heritability is a complicated term, with a very specific meaning that can be misinterpreted. Perhaps the most important thing to take away is that a high heritability estimate does not mean that the environment is not important. Schools and teachers have a crucial impact on students’ learning, and high heritability likely reflects the fact that all students sampled are exposed to high quality learning environments.

“With a shared understanding of what heritability means, we can start to have meaningful debates about what we want our education systems to achieve.”

As our understanding of the role of genes in learning increases, it is essential that discussions are based on common terminology. Heritability is a good place to start. With a shared understanding of what heritability means, we can start to have meaningful debates about what we want our education systems to achieve.

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