Scientists are building powerful predictors of our educational attainment based on genetic information. These ‘polygenic scores’ measure the genetic load that individuals carry for a specific trait, which in this case, is educational attainment or years spent in education. Considered individually, genetic variants have tiny effects, but when these are added up into a polygenic score, they explain a considerable proportion of the variability that is seen in educational outcomes across a population (up to 16% in school achievement1.
This ability to explain variation means that polygenic scores are described as game changers, rivalling other standard predictors of how well we do on our educational journeys such as family socioeconomic status2. Although polygenic scores for educational attainment are not able to predict how far one particular person goes in education, they are valuable tools for population-level research, for example on the mechanisms and consequences of social change3 and social mobility4.
However, we need to know where the predictive value of polygenic scores for educational attainment stems from, and it’s not only genes…
Our new study published in the journal Psychological Science provides evidence that a considerable fraction of the predictive value of polygenic scores for education actually comes from the influence of the home environment provided by genetic relatives.
To study the complex entwining of the influences of genes and the home environment on education, we drew upon the classic ‘natural experiment’ for disentangling nature and nurture – adoption. Figure 1 below depicts how comparing adopted and non-adopted individuals allows us to extricate genetic influences from environmental effects5.
In genetically related families (left figure), children’s polygenic scores for education are associated with their own educational attainment, but they are also correlated with their parents’ genetic variation. This parental genetic variation influences child education indirectly, via parental behaviours that shape the home environment, such as reading books together or a passion for crosswords. Indeed these parent-driven effects might be accentuated at a time like this, when schools are closed due to the COVID-19 pandemic and parents and children are interacting even more than usual.
Without adjusting for these indirect effects of parental genetics on child education, estimates of effects of children’s polygenic scores may be inflated, since they reflect effects of the child’s genes and environmentally mediated effects of the parent's genes.
In contrast, when children are adopted (right side of diagram below), the link between their polygenic scores for education and the family environment is broken, because adoptees are not genetically related to the parents. Therefore, their polygenic score can only be connected to their educational outcome ‘directly’ without any indirect influences of their parents’ genes acting through the environment.