Q: Have you read the latest issue of PLoS One?
A: What do you mean? PLoS One doesn’t have “issues”, it’s online-only and publishes papers as soon as they are ready.
Q: Well, have you read the study that led to the headline ‘exam results are influenced by genes, not schools‘, which the Herald says is in the latest issue of PLoS One?
A: Perhaps they mean this paper about heritability of exam results.
Q: Yes, that one. Couldn’t they have just linked to it?
A: My sources tell me linking is harder than it looks.
Q: Whatever. How did they find out that schools don’t matter?
A: That’s not quite what they found out.
Q: Well, they found 60% of education was due to genes, not schools, didn’t they?
A: What would that even mean?
Q: I thought I got to ask the questions.
Q: Ok, what did they find?
A: They found that identical twins had a correlation of about 0.8-0.9 between their exam results, and non-identical twins had a weaker correlation, about 0.5-0.6. If you assume that the only difference between identical and non-identical twin pairs is that the identical twins share more genes, and that the genetic and non-genetic contributions just add, you can estimate how much of the variation between twins was due to genes and how much is due to environmental factors. And they end up with estimates from 40% to 60% for the genetic part.
Q: How is that different from the headline?
A: The effects aren’t going to be additive in reality — genetics isn’t going to let you pass a British history test if you haven’t ever studied any British history – so the heritability is just a summary of variation in the current population under the current conditions. What the study really finds is that British schools currently differ from each other less than British kids do. If you made a lot of kids from Beijing or Buenos Aires take the British GCSE tests (or vice versa) they’d probably do really badly, and that would definitely be due to their schooling, not their genes.
Q: And what do the researchers say?
A: Pretty much what I said. The Herald quotes them further down in the story
“Since we are studying whole populations, this does not mean that genetics explains 60 per cent of an individual’s performance, but rather that genetics explains 60 per cent of the differences between individuals, in the population as it exists at the moment.
“This means that heritability is not fixed – if environmental influences change, then the influence of genetics on educational achievement may change too.”
Q: If schools were improved, would the heritability of exam results increase or decrease?
A: That’s a very interesting question. We don’t know. It could be that better schools would have more benefits for people who currently do poorly for genetic reasons, and would reduce heritability; it could be that they would have more benefits for people who currently do poorly for environmental reasons, and would increase heritability; it could be that they would have more benefits for people who currently do well for genetic reasons, and would increase heritability; it could be that they would have more benefits for people who currently do well for environmental reasons, and would decrease heritability. Or it could be that they wouldn’t use exams.
Q: What does this research tell us about the UK’s falling position on the PISA international education comparison? Or is that the fault of Facebook and email, like the UK Schools Minister says?
A: Well, it’s not genetic. The genes of the UK population don’t change fast enough. It’s probably not due to Facebook, either, but at least that’s conceivable.
Q: Are the results surprising?
A: Not especially. Similar correlations are seen in IQ test results, where we do know from changes over time that environmental differences can have a large impact. It’s a bit surprising that test scores are slightly more heritable than IQ test results.
Q: Could you give a less controversial example, perhaps something like height?
A: Height is an excellent example. The fact that siblings have similar heights shows the large genetic component when environments are similar; the fact that most people are taller than their parents or grandparents shows the large environmental component when genetics are similar. If you look in a wealthy Western country, height is about 80% heritable. In medieval Europe it would have been much more sensitive to environment, since the nobility were much healthier and better-nourished than the peasants. And if you mixed together people from medieval Europe and modern Europe, about half the variability would be due to which era they came from.