Focus on Words: A Twin Study of Reading and Inattention

Abstract

The etiology of variation in reading ability and its relationship to inattention, impulsivity, and general cognitive ability were investigated within a large, population-based sample of 9- to 10-year-old twins. Phenotypic and genetic analyses were performed on word-level reading, full-scale IQ, and measures of inattention and impulsivity derived from the Go-NoGo task (i.e., Go errors and NoGo errors, respectively). Moderate and significant phenotypic correlations were found among reading, inattention and IQ, but not between impulsivity and the other variables. Genetic modeling revealed that genetic and shared environmental influences largely accounted for variation in reading, inattention, and IQ and covariation among them, whereas specific environmental influences contributed primarily to variation in impulsivity. Acting through a common factor, a portion of the genetic influences on reading ability appeared to be shared with influences affecting IQ as well as those affecting inattention. The contribution of phonological awareness to the remaining unique genetic influences on reading was explored through additional analyses. A two-common-factor model was revealed, with a strongly genetic general cognitive ability factor affecting reading, inattention, and IQ, and an equally strongly genetic second common factor, which captured the variability in reading ability that was related specifically to phonological processing. The processes involved in reading, therefore, seem to involve genetic and environmental influences that are part of both a general cognitive system and a system more specific to reading and phonology.

The Genetic Association Between ADHD Symptoms and Reading Difficulties: The Role of Inattentiveness and IQ

“…Therefore, it is possible that any shared genetic variability between inattention symptoms and reading disability could reflect a common genetic association shared with general intelligence. This idea was supported by evidence that genetic and environmental influences shared with IQ accounted for the covariance between reading performance and a cognitive attention measure (Zumberge et al 2007 ). However, it is not possible to generalize directly from cognitive attention processes to behavioural inattention problems (Marzocchi et al 2009 ; Warner-Rogers et al 2000 ).…”

A twin and adoption study of reading achievement: Exploration of shared-environmental and gene–environment-interaction effects

“…Most twin studies of reading suggest minimal contribution of shared environmental factors. For example, the previously mentioned twin studies by Harlaar et al (Harlaar, et al, 2007), Gayán and Olsen (Gayan & Olson, 2003) and, Zurnberge et al (Zurnberge, et al, 2007) all concluded that shared environmental factors accounted for 10% or less of the phenotypic variance in reading. Nonetheless, the estimation of shared environmental effects in a twin study is indirect (i.e., based on a comparison of monozygotic and dizygotic twin similarity), and estimates might differ when more direct approaches, such as an adoption study, are used.…”

“…Similarly, in a sample of 440 twins age 8 to 18, Gayán and Olsen (Gayan & Olson, 2003) reported heritability estimates of 80% or higher for 4 different measures of reading performance (e.g., word recognition, phonological decoding). Finally, in a community based sample of 605 pairs of twins age 10 years, Zurnberge et al (Zurnberge, Baker, & Manis, 2007) reported a heritability estimate of 70% for reading as assessed by subtests from the Woodcock–Johnson Tests of Achievement. Importantly, not only are reading disability and reading abilities substantially heritable, but the influence of genetic risk factors for reading disability appears to be of comparable magnitude to those that contribute to individual differences in reading-related phenotypes throughout the normal range (Bates, et al, 2007; Hawke, Wadsworth, Olson, & DeFries, 2007).…”

Inattention, Hyperactivity, and Emergent Literacy: Different Facets of Inattention Relate Uniquely to Preschoolers' Reading-Related Skills

“…Although some authors have proposed a reciprocal causal relation between behavior problems and reading (i.e., difficulties in one domain exacerbate problems in the other; see Spira & Fischel, 2005 for review), recent genetic research has pointed to possible underlying mechanisms that simultaneously influence both domains (Cornish, Savage, Hocking, & Hollis, 2011; Hart, et al, 2010). Research with older children has shown that it is most likely the inattention, rather than the hyperactivity, component that accounts for the relation between ADHD and reading (e.g., Zumberge, Baker, & Manis, 2007). Whereas the link between inattention and reading is well documented in older children, less is known about the relations between inattentive and hyperactive/impulsive behaviors and reading-related skills when they first emerge in the preschool years.…”