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Petrill, S. A. (2013). Relating reading comprehension to language and broader reading skills. In B. Miller, L. Cutting, & P. McCardle (Eds.), Unraveling reading comprehension: Behavioral, neurobiological, and genetic components (pp. 193–202). Baltimore, MD: Brookes.

Summary by Dr. Michael Solis

Overview

Have you ever wondered how a person’s genetic makeup affects his or her ability to read? Genetic factors are always involved in the development of complex human skills. Behavioral genetics is a field that tries to measure how much of an ability’s development can be attributed to genes versus the environment. By taking into account both genetic and environmental factors and relating the findings to the brain network that supports reading, researchers continue to gain a better understanding of how an individual’s genetic makeup affects his or her ability to read. The article by Petrill highlights what we have learned from behavioral genetic studies of reading and provides insight into the underling mechanisms of reading comprehension development.

Behavioral Genetic Studies of Reading Comprehension

The study of identical twins and fraternal twins has provided insight into the age-old question of nature versus nurture. These studies suggest that genetic differences account for a significant proportion of the differences in reading comprehension for both typically developing readers and readers with disabilities (Astrom, Wadsworth, Olson, Willcutt, & DeFries, 2012; Petrill et al., 2007). Other studies suggest that reading comprehension and related factors, such as decoding, phonological processing, and language skills, are “highly heritable” and influenced by the environmental features that twins share, such as the school they attend (Harlaar, Spinath, Dale, & Plomin, 2005; Keenan, Betjemann, Wadsworth, DeFries, & Olson, 2006). Petrill also highlights evidence that young children identified with a language disability are potentially at risk for developing a reading disability partially due to shared genetic factors. Researchers have used behavioral genetic analysis of family members to examine differences in reading and language skills, taking into account family history of language impairments or reading problems. As Petrill reports, these behavioral genetic studies help to explain many of the distinctions found in the reading literature, including individual differences in reading and how these differences are influenced by a complex network of environmental and genetic effects.

Brain Imaging and Genetics

An extensive body of literature examines neuroimaging of typically developing readers and readers with disabilities. Petrill points to findings from such studies that suggest that neuroanatomical regions of the brain are related to reading, including differences between typically developing readers and readers with disabilities. In very general terms, studies of typically developing readers show consistent patterns of left-hemisphere activation in the brain, which is associated with fast and efficient reading. Studies of readers who struggle show underactivation of left-hemisphere regions of the brain and greater activation in right-hemisphere regions of the brain when compared to typically developing readers. Petrill points to further study findings that students who did not respond to reading intervention showed decreased connectivity in key pathways that connect specific regions of the brain and differences in the integrity of these pathways between typically developing students and students with reading disabilities.

How These Findings Affect Reading Instruction and Placement Decisions

It is imperative, Petrill concludes, that parents and teachers take into account a student’s family history of difficulties with speech, language, and reading when considering instruction. First and foremost, it is important to gather as much information as possible about immediate and extended family members who had difficulties with speech or reading. The more specific the information, the more likely it will provide valuable insight into identifying a reading or language problem early in development, allowing educators to provide appropriate interventions. Genetic associations do not mean that a reading problem cannot be successfully addressed. However, a child in first grade with a family history of reading disability—particularly an immediate family member identified with a reading difficulty at an older age—may need to stay in a reading intervention for a longer period of time than other students, even if testing data indicate adequate intervention response.

Parents and teachers need to think about and take into account the family history of children as part of reading intervention decisions. The study of behavioral genetics strongly suggests that genetics do play a role in the development of reading skills.

Summary

Behavioral genetic studies and brain imaging provide a better understanding of the differences of individuals as a means to more quickly identify and treat reading problems. Studies of behavioral genetics provide plausible explanations of differences in reading comprehension, reading comprehension deficits, and the development of reading comprehension and related domains, such as decoding and language. When practitioners and parents think about reading interventions for students, it is important to consider family history. Just as the study of genetics for medical conditions (e.g., heart disease) has contributed to a better understanding of early interventions and long-term treatment, over time, the identification of genetic risk in reading comprehension may lead to better decision-making about early reading intervention and the appropriate level of intervention intensity.

References

Astrom, R. L., Wadsworth, S. J., Olson, R. K., Willcutt, E. G., & DeFries, J. C. (2012). Genetic and environmental etiologies of reading difficulties: DeFries-Fulker analysis of reading performance data from twin pairs and their non-twin siblings. Learning and Individual Differences, 22(3), 365–369.

Harlaar, N., Spinath, F. M., Dale, P. S., & Plomin, R. (2005). Genetic influences on early word recognition abilities and disabilities: A study of 7-year-old twins. Journal of Child Psychology and Psychiatry, 46(4), 373–384.

Keenan, J. M., Betjemann, R. S., Wadsworth, S. J., DeFries, J. C., & Olson, R. K. (2006). Genetic and environmental influences on reading and listening comprehension. Journal of Research in Reading, 29(1), 75–91.

Petrill, S. A., Deater-Deckard, K., Thompson, L. A., Schatschneider, C., DeThorne, L. S., & Vandenbergh, D. J. (2007). Longitudinal genetic analysis of early reading: The Western Reserve reading project. Reading and Writing, 20(1–2), 127–146.


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