Stop, before you start taking your books and maybe wake up your kids to practice reading, first read this piece. A study of 1,890 identical twins has found that strong early reading skill might correlate with later intelligence. The twins, who are part of an ongoing longitudinal study in the United Kingdom, share all their genes as well as a home environment. Differences shown in intellectual ability came from experiences they didn’t share. The twin with stronger early reading skills was found to have higher overall intellectual ability by age 7.

As you will read, the researchers think there might be a causal effect although they keep their reserves. They argue that the research implies a causal relation as they focused on identical twins (genes are the same), and we know there is a big correlation in IQ between identical twins. So differences in the IQ come from the environment, is the basic idea, reading being one of the elements in the environment.

Well, what we do know: reading skills do help, reading helps reading skills, so, maybe don’t wake up your kids, but do promote reading.

From the press release:

“Since reading is an ability that can be improved, our findings have implications for reading instruction,” according to Stuart J. Ritchie, research fellow in psychology at the University of Edinburgh, who led the study. “Early remediation of reading problems might aid not only the growth of literacy, but also more general cognitive abilities that are of critical importance across the lifespan.”

Researchers looked at 1,890 identical twins who were part of the Twins Early Development Study, an ongoing longitudinal study in the United Kingdom whose participants were representative of the population as a whole. They examined scores from tests of reading and intelligence taken when the twins were 7, 9, 10, 12, and 16. Using a statistical model, they tested whether differences in reading ability between each pair of twins were linked to later differences in intelligence, taking into account earlier differences in intelligence. Because each pair of identical twins shared all their genes as well as a home environment, any differences between them had to be because of experiences that the twins didn’t share, such as a particularly effective teacher or a group of friends that encouraged reading.

The researchers found that earlier differences in reading between the twins were linked to later differences in intelligence. Reading was associated not only with measures of verbal intelligence (such as vocabulary tests) but with measures of nonverbal intelligence as well (such as reasoning tests). The differences in reading that were linked to differences in later intelligence were present by age 7, which may indicate that even early reading skills affect intellectual development.

“If, as our results imply, reading causally influences intelligence, the implications for educators are clear,” suggests Ritchie. “Children who don’t receive enough assistance in learning to read may also be missing out on the important, intelligence-boosting properties of literacy.”

Besides having implications for educational intervention, the study may address the question of why individual children from one family can score differently on intelligence tests, despite sharing genes, socioeconomic status, and the educational level and personality of parents with their siblings.

Abstract of the study:

Evidence from twin studies points to substantial environmental influences on intelligence, but the specifics of this influence are unclear. This study examined one developmental process that potentially causes intelligence differences: learning to read. In 1,890 twin pairs tested at 7, 9, 10, 12, and 16 years, a cross-lagged monozygotic-differences design was used to test for associations of earlier within-pair reading ability differences with subsequent intelligence differences. The results showed several such associations, which were not explained by differences in reading exposure and were not restricted to verbal cognitive domains. The study highlights the potentially important influence of reading ability, driven by the nonshared environment, on intellectual development and raises theoretical questions about the mechanism of this influence.