Children who are avid readers are typically good readers, and children who seldom read a book voluntarily often have dyslexia. Is their reading ability the consequence of how much they practised? Or do good readers enjoy books more than dyslexics? Psychologists and behavioural geneticists from the Vrije Universiteit Amsterdam, in collaboration with the University of Oxford, studied this in 6,000 7-year-old twin pairs. They discovered that how well children read influences how much they read, and not the other way around. Furthermore, they found that how well children read is very heritable, while how much they read is influenced equally by genes and the environment.
The good readers all read a book for pleasure now and then, and almost half of them even daily. Only 1 out of 5 of the struggling readers read daily, and 1 out of 10 never read. It was known that how much you do something and how well you do it are related, but for reading this study seems to solve the chicken-and-egg problem. The scientists could estimate heritability by applying sophisticated statistics on the large set of twin data. The study is published in the influential Journal of Child Psychology and Psychiatry ‘Why do children read more? The influence of reading ability on voluntary reading practices’, Elsje van Bergen et al.
Dyslexia is heritable
How easily children learn to read turns out to be heritable. Genetic differences account for most of the differences among children in reading ability. Reading ability, in turn, influences how much children read for pleasure. “So, children do not have dyslexia because they prefer doing something other than reading after school. Having said that, we know that children with (or at risk for) dyslexia benefit from remedial teaching.” according to biological psychologist Elsje van Bergen.
Heritability research in twins
Parents of 7-year-old twins answered questions of the Netherlands Twin Register about how much and how well their children read. The teachers also indicated how well the children read and how well they score on tests of reading fluency. The special thing about data from twins is that you can study the contribution of genes and environment to individual differences. Identical twins inherit exactly the same genetic code, while fraternal twins are genetically speaking just like ordinary siblings. Identical twins resemble each other more in reading than fraternal twins do. This difference was larger for reading ability than reading amount, which shows that reading ability is more heritable.
If you are interested in these studies more can be found at this link.
This release comes from Vrije Universiteit Amsterdam. It is independent and does not necessarily reflect the views of ACAMH.