How much of educational achievement is genetic?
A new study published in PNAS used a twin studies approach of UK students to examine the heritability of a wide range of traits associated with educational achievement.
Observations: Heritability measures the degree to which a trait’s variation is determined by genes vs the environmental influences on a population level. Heritability is generally reported as a number between 0 (not genetic at all) to 1 (completely genetic).
IQ has been measured to have heritabilities between 0.5 and 0.8, which indicates a considerable genetic component to explain variation. (There is also a long history of debate surrounding the confounding factors to these measurements, including the importance of the test, the construction of the test, etc.) There are known heritable differences in educational achievements. This has been established using the twin studies approach, where monozygotic (identical; 100% genetic match) and dizygotic (fraternal; 50% genetic match) twins are compared in terms of performance on educational assessments.
Hypotheses: Examination of many other parameters including health, home environment, self-efficacy, etc., may help explain the high heritability and especially identify what environmental parameters can be targeted for intervention most effectively.
Methods: Over 6500 pairs of twins participating in a longitudinal study in the UK who took the General Certificate of Secondary Education (GCSE) exam at age 16. These same individuals and their parents answered a questionnaire and were interviewed by phone.
Nine areas of additional measures (condensed from 83 separate measurements) were identified to be used in a predictive model for GCSE score using the data collected. These included general intelligence in a non-IQ test, educational self-efficacy, child-reported personality, child-reported well-being, parent-reported behavioral problems, child-reported behavioral problems, child-reported health, child-reported school environment, and child-reported home environment. Comparisons of monozygotic and dizygotic twins were used in a variety of statistical tests examining each factor by itself and multiple factors together. These comparisons were used to measure how much they each contribute to the heritability of the GCSE.
Results: GCSE showed the greatest heritability, followed by intelligence, parent identified behavioral problems, and health.
The multivariate comparisons showed that the nine areas accounted for 75% of the heritability seen in the GCSE.
Genetic influence is greater for achievement than for intelligence, and other behavioral traits are related to educational achievement largely for genetic reasons.
This conclusion is based on the multivariate analyses described above, and is an unexpected results as many would assume that achievement would be more environmentally affected than intelligence. The areas measured show that major aspects of schooling are affected a great deal by genetics, including self-efficacy, personality traits, and behavioral problems.
However, it is always useful to point out that heritability, while a useful metric, does not measure the proportion of a trait determined by genes directly, but how much variation is explained by them. That means that while there is a lot of the trait that is under genetic control, it isn’t set in stone.
This paper highlights that there are major areas that educators can focus on to improve education achievement and in ways that can take advantage of the covariance of these traits. Environmental components such as the school environment, which was shown to have high heritability, are obviously available for manipulation to improve achievement.