Longitudinal Genetic Analysis of Early Reading: The Western Reserve Reading Project

Abstract

We examined the genetic and environmental contribution to the stability and instability of reading outcomes in early elementary school using a sample of 283 twin pairs drawn from the Western Reserve Reading Project. Twins were assessed across two measurement occasions. In Wave 1, children were either in kindergarten or first grade. Wave 2 assessments were conducted one year later. Results suggested substantial genetic stability across measurement occasions. Additionally, shared environmental influences also accounted for stability, particularly for variables more closely tied to direct instruction such as phonological awareness, letter knowledge, and word knowledge. There was also evidence for independent genetic and shared environmental effects, suggesting that new sources of variance may emerge as the demands of school change and children begin to acquire early reading skills.

Word reading and reading comprehension: stability, overlap and independence

“…The Longitudinal Twin Study of Early Reading Development (LTS; see Byrne et al, 2002 for overview) has been studying prereading and reading skills developmentally, so far reporting on over 600 pairs of children tested in preschool and kindergarten. The Western Reserve Reading Project (WRRP; Petrill et al, 2007) has investigated reading measures in 350 twin pairs who are slightly older, but still in the very early stages of reading development, testing children through the second grade. Both of these studies have found shared genetic influences between time points, as well as genetic influences unique to the second assessment, for component measures of reading.…”

“…It is also possible that the etiology of this development could continue to change. However, to our knowledge, the etiology of the stability of comprehension has only been studied in children through the second grade (Petrill et al, 2007), so there is no prior evidence as to whether there are indeed changes in the etiology of comprehension at later ages. Thus, the current study assesses the stability of both reading comprehension and word reading in these later years of development.…”

“…Moreover, the emphasis on comprehension in reading and reading instruction increases around the middle-elementary school years, when the demands of reading transition from ''learning to read'' to ''reading to learn'' (e.g., Catts, Hogan, & Adlof, 2005;Chall, 1983;Harlaar et al, 2007;Leach, Scarborough, & Rescorla, 2003), making it especially important to include data from older children in the assessment of the etiology of its stability. Despite this, no previous studies have assessed longitudinal etiology of comprehension using genetically informative data from children beyond the second grade (Petrill et al, 2007). Thus, in the current study we explore the etiologies of stability of both word reading and reading comprehension in older children tested at 5-6-year intervals, and assess how the relationship between these skills may change over time.…”

“…Univariate heritability estimates for word reading skill and related reading components range from .30 to .85 (e.g., Byrne et al, 2005a;DeFries et al, 1997;Gayán & Olson, 2003;Harlaar, Spinath, Dale, & Plomin, 2005;Petrill, Deater-Deckard, Thompson, DeThorne, & Schatschneider, 2006a;Stevenson, Graham, Fredman, & McLoughlin, 1987;Tiu, Wadsworth, Olson, & DeFries, 2004;Wadsworth, Corley, Hewitt, & DeFries, 2001;Wadsworth, Corley, Plomin, Hewitt, & DeFries, 2006). While word reading and its related components are most often studied, some researchers have also assessed genetic influences on reading comprehension and have noted similar heritability estimates, in the range of .41 to .76 (e.g., Byrne et al, 2005b;Harlaar, Dale, & Plomin, 2007;Keenan, Betjemann, Wadsworth, DeFries, & Olson, 2006;Petrill, Deater-Deckard, Thompson, Schatschneider, DeThorne, & Vandenbergh, 2007). Given that word reading and comprehension skills are both stable and heritable, we hypothesize that this stability may be due to genetic influences.…”

Colorado longitudinal twin study of reading disability

“…However, relatively little is known about the etiology of developmental stability and change in reading disability. Genetically informative designs, such as twin, adoption, or molecular genetic family studies, are needed to address these issues, and such studies of reading ability and disability are relatively recent (e.g., Astrom, Wadsworth & DeFries, 2007;Byrne et al, 2007;Harlaar, Dale & Plomin, 2007;Lyytinen et al, 2001;Moffitt, 2002;Petrill et al, 2007;Wadsworth, Corley, Plomin, Hewitt & DeFries, 2006).…”