Large twin study finds that reading really does increase intelligence

Study of twins finds reading does make you smarterDid you ever have a teacher or parent tell you reading makes you smarter? While they were probably just trying to make you read more, it turns out there’s new research to back it up. Improving reading skills early can pay dividends later in intelligence and reading level, according to reasearchers.

A large longitudinal twin study in England and Wales finds that twins who have better reading ability scores than their genetically identical siblings at age 7 score higher in follow-up reading and intelligence testing at ages 9, 10, 12, and 16 years.

The 1,890 monozygotic twin pairs in the study were born between January 1994 and December 1996 and raised in the same families, making it possible for researchers to rule out genetic and environmental effects to account for different outcomes.

“Twins with better earlier reading ability compared to their identical cotwin tended not only to have better reading at subsequent measurements but also higher scores on general intelligence tests,” the researchers write in Child Development.

“We also found that the associations are not restricted to possible effects of reading on the verbal domain—mainly affecting vocabulary and general knowledge—but extend to associations of reading with nonverbal intelligence.”

“In other words, reading may, over time, improve general intelligence.”

The results provide compelling evidence that early reading interventions may not only aid in the development of literacy but may also improve general cognitive abilities that are critical across a lifespan.

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Differences in reading ability

What if one twin just liked reading more than the other? Couldn’t the different outcomes be a matter of one twin reading more rather than reading ability?

To account for differences in reading exposure, researchers analyzed scores on the Author Recognition Test (ART) which the children took at ages 10 and 12. This online test presents children with a list of 42 author names, half of which were names of popular children’s authors and half of which were foils. Children are asked to click on the names of real authors, clicking as many or as few as they wish. The researchers found no association between reading exposure and intelligence scores.

Besides controlling for reading exposure and interest and  genetic and environmental effects, the research model also controlled for potential influences such as an effective teacher that could improve reading and intelligence for one twin and not the other. To control for these potential influences, researchers considered the stability of traits across time (from ages 7-16).

What mechanism would account for the difference in reading ability in one twin?

“There are many candidates for such mechanisms, all of which may independently influence the reading of one twin from a pair. For instance, effective, high-quality teachers, academically focused peer groups, or specific literature encountered by one twin but not by the other may boost the reward value of learning to read or increase the effectiveness or duration of reading practice,” the researchers write.

Whatever the mechanism for better reading ability at age 7, the study re-emphasizes the importance of early reading interventions to improve reading skills.

“Does Learning to Read Improve Intelligence? A Longitudinal Multivariate Analysis in Identical Twins From Age 8 to 16,” by Stuart Ritchie et al., Child Development, February 2015, Volume 86, Number 1, pp. 23-36.

3 Responses to “Large twin study finds that reading really does increase intelligence”

  1. Angela

    How do they account for the possibility that the younger child with higher reading abilities also started with higher intelligence, which could also help explain why he or she was the better reader early on?

    Reply
  2. Karen Linnebur

    I have twins born in 1993 (a girl and a boy). Your study is true for my children. Thank you.

    Reply
  3. Karen Linnebur

    I have twins that were born in Dec. of 1993. We read many books to them when they were babies and on up through grade school. They made great gains! It is so amazing to remember the length and depth of books that they read on their own.
    That was a wonderful time in my life!
    They both are in college and are still responsible.
    We had four older children also. All went to college and are leading responsible lives. Each have 2 children.

    Reply

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