Genetic and environmental influences on reading and listening comprehension

We report preliminary behaviour genetic analyses of reading and listening comprehension from The Colorado Learning Disabilities Research Center. Although the twin sample with these new measures is still of limited size, we find substantial, and significant, genetic influences on individual differences in both reading and listening comprehension. In addition, word recognition and listening comprehension each accounted for significant independent genetic influences on reading comprehension. Together, they accounted for all the genetic influence on reading comprehension, indicating a largely genetic basis for the ‘simple model’ of individual differences in reading comprehension proposed by Hoover and Gough (1990) .     

Genetic and Environmental Etiologies of the Longitudinal Relations Between Prereading Skills and Reading

The present study explored the environmental and genetic etiologies of the longitudinal relations between prereading skills and reading and spelling. Twin pairs (n = 489) were assessed before kindergarten (M = 4.9 years), post‐first grade (M = 7.4 years), and post‐fourth grade (M = 10.4 years). Genetic influences on five prereading skills (print knowledge, rapid naming, phonological awareness, vocabulary, and verbal memory) were primarily responsible for relations with word reading and spelling. However, relations with post‐fourth‐grade reading comprehension were due to both genetic and shared environmental influences. Genetic and shared environmental influences that were common among the prereading variables covaried with reading and spelling, as did genetic influences unique to verbal memory (only post‐fourth‐grade comprehension), print knowledge, and rapid naming.     

Genetic and environmental bases of reading and spelling: A unified genetic dual route model

We develop and test a dual-route model of genetic effects on reading aloud and spelling, based on irregular and non-word reading and spelling performance assessed in 1382 monozygotic and dizygotic twins. As in earlier research, most of the variance in reading was due to genetic effects. However, there were three more specific conclusions: the first was that most of the genetic effect is common to both regular and irregular reading. In addition to this common variance evidence was found for distinct genes influencing the acquisition of a lexicon of stored words, and additional genetic effects influencing the acquisition of grapheme–phoneme correspondence rules. The third conclusion, from a combined model of reading and spelling, is that reading and spelling have a common genetic basis. Models that did not distinguish lexical and non-lexical performance fit significantly worse than dual route genetic models. An implication of the research is that models of reading, whether connectionist or dual-route, must allow for the genetic independence of neurological processes underlying the decoding of non-words and irregular words.     

Language Impairment and Reading Disability: Connections and Complexities Introduction to the Special Issue

Researchers and practitioners in the fields of reading and language are well informed about the importance of phonological awareness in beginning reading. The purpose of this special issue of Learning Disabilities Research & Practice is to present recent research that extends the search for language and reading connections beyond the realm of phonological awareness. Many children with language impairment (LI) identified before formal schooling experience persistent difficulty in learning to read. Two interrelated issues are prerequisite for understanding the developmental course of events that might link language and reading (dis)ability in these children. One is an appreciation of exactly what is meant by LI, while the second concerns how LI should be explained. In this introductory article, we explore the complexities of these two issues, in particular the controversy between the domain‐specific perspective and the domain‐general perspective on the nature of specific LI (SLI). Consistent with these perspectives, future studies on possible language‐reading links will need to measure language and related processes in greater breadth and depth, over time, and within a variety of experiential contexts. The five articles in this issue represent a critical first step in this direction.     

Genetic and environmental mediation of the prediction from preschool language and nonverbal ability to 7‐year reading

We use a genetically sensitive design to examine the relationship between language and nonverbal ability at 4½ and reading skills at 7 years of age in a sample of more than 1,000 children participating in the Twins Early Development Study. We find that nonphonological as well as phonological measures of early language make significant contributions towards the prediction of reading at 7, and that nonverbal ability at 4½ is an equally strong predictor. With respect to aetiology, we find substantial genetic contributions towards the relationship between early language skills and reading at 7, as well as a trend towards shared environmental influences. The genetic continuity is not specific to the verbal domain, however, as we also find a substantial genetic relationship between nonverbal ability at 4½ and reading at 7.     

A comparative analysis of cognitive profiles: Monozygotic and dizygotic reading-disabled twins

Previous twin studies have provided evidence for genetic influences on reading disability (RD) or normal reading ability. The existence of subtypes of RD — each with its characteristic cognitive profile — has been suggested. Whether the etiology of the particular subtypes is genetic is uncertain. The present study examined within-pair comparisons of cognitive profiles (with respect to composites of general reading, symbol processing speed and sequential memory) in RD and control twins. Twin profile analysis were applied to these cognitive composites on 120 pairs of RD and control twins. Results showed a greater monozygotic (MZ) than dizygotic (DZ) resemblance in profiles indicating that individual differences in the patterning of cognitive abilities related to reading are genetically influenced.     

Word reading and reading comprehension: stability, overlap and independence

Longitudinal twin data were analyzed to investigate the etiology of the stability of genetic and environmental influences on word reading and reading comprehension, as well as the stability of those influences on their relationship. Participating twin pairs were initially tested at a mean age of 10.3 years, and retested approximately five years later. Both word reading and comprehension were found to be highly stable, and genetic influences were primarily responsible for that stability. In contrast to studies with younger participants, no unique genetic influences were observed at follow-up testing in this older sample. High genetic correlations were obtained between word reading and reading comprehension at both ages, indicating common genetic influences. However, significant genetic influence on comprehension was also observed, independent of that on word reading. Although the phenotypic relation between the two measures appeared to decline across time, the genetic etiology of this relation was highly stable.     

Genes, environment, and dyslexia the 2005 Norman Geschwind memorial lecture

This article presents an overview of some methods and results from our continuing studies of genetic and environmental influences on dyslexia, and on individual differences across the normal range that have been conducted over the past 25 years in the Colorado Learning Disabilities Research Center (CLDRC) and in related projects. CLDRC investigators compare the similarities of identical twin pairs who share all their genes and fraternal twins who share half their segregating genes to assess the balance of genetic, shared family environment, and nonshared environment influences on dyslexia and on individual differences across the normal range. We have learned that among the children we have studied in Colorado, group deficits in reading (dyslexia) and individual differences in reading across the normal range are primarily due to genetic influences, and these genetic influences are often shared with some of the same genetic influences on deficits and individual differences in language and ADHD. We have also learned from our molecular-genetic linkage studies that there are regions on several chromosomes likely to contain genes that influence dyslexia. Several specific genes within these regions have been tentatively identified through molecular-genetic association analyses, but much more research is needed to understand the pathways among specific genes, regions of noncoding DNA that regulate the activity of those genes, the brain, and dyslexia. I conclude with a discussion of our research on individual differences in early reading development, on the role of early learning constraints in dyslexia, and on how genetic influences are expressed through their interaction and correlation with the environment.     

Predicting individual differences in reading comprehension: a twin study

We examined the Simple View of reading from a behavioral genetic perspective. Two aspects of word decoding (phonological decoding and word recognition), two aspects of oral language skill (listening comprehension and vocabulary), and reading comprehension were assessed in a twin sample at age 9. Using latent factor models, we found that overlap among phonological decoding, word recognition, listening comprehension, vocabulary, and reading comprehension was primarily due to genetic influences. Shared environmental influences accounted for associations among word recognition, listening comprehension, vocabulary, and reading comprehension. Independent of phonological decoding and word recognition, there was a separate genetic link between listening comprehension, vocabulary, and reading comprehension and a specific shared environmental link between vocabulary and reading comprehension. There were no residual genetic or environmental influences on reading comprehension. The findings provide evidence for a genetic basis to the “Simple View” of reading.     

Responsiveness to General Education Instruction as the First Gate to Learning Disabilities Identification

Most definitions of learning disabilities (LD) include a qualification that adequate general education instruction was received and the child with LD did not benefit. Rarely is this tenet assessed in either practice or research before a diagnosis is made. We review three studies that investigated children's responsiveness to general education reading instruction as an indicator of need for more intensive interventions. Adequacy of instruction was quantified by children's level and rate of progress, compared to classmates, as measured by curriculum‐based measures of oral reading fluency. We found that the response‐to‐instruction model tested was valid in that (1) children who differ from their peers on level and slope of performance (dual discrepancy) have more severe academic and behavioral problems than children who have IQ‐achievement discrepancies or low achievement; (2) children who demonstrate persistent nonresponsiveness over three years differ from other at‐risk children on reading, reading‐related, and behavioral measures; and (3) at‐risk children who participated in specially designed general education interventions had better outcomes than at‐risk children who did not participate. We conducted additional analyses to assess low achievement definitional variations and found that they lack sensitivity and coverage compared to a dual discrepancy definition.     

A Strategy for Assessing Problems in Word Recognition among Dyslexics

The article argues for the importance of studying word‐recognition strategies in the assessment of dyslexia. The consensus model of word recognition in cognitive neuropsychology, the dual‐route model, is critically discussed in the light of attacks from computational models in modern connectionism. Despite the criticism, it is argued that a dual‐route model can serve important functions in the context of dyslexia assessment. We propose a specific version of the dual‐route model from which we construct a series of tasks for diagnosing subprocesses in word recognition. A computer‐based test battery is described, involving oral reading tasks, lexical decision, rhyme detection, letter categorization, visual analysis, naming, and semantic categorization. Latencies and accuracy scores are recorded. The usefulness of this assessment approach is demonstrated in two case studies of 15‐year‐old dyslexic boys.     

Personal and Social-Contextual Factors in K–12 Academic Performance: An Integrative Perspective on Student Learning

Our extensive literature review in the fields of educational, social, and cognitive psychology has led us to identify about a dozen variables that demonstrate direct empirical links to academic achievement at the K–12 level. Those variables are grouped into four major categories: student engagement, learning strategies, school climate, and social-familial influences. We then categorize the first two variables as personal factors and the latter two as social-contextual factors. We document empirical findings that have shown particular relationships between the reviewed personal and social-contextual factors and academic achievement, mainly in the areas of reading and mathematics. Based on our conceptualization, we propose an integrated perspective that students’ personal factors in the domains of behavior, affect, attitude, and cognition as well as their social-contextual environment have to work in concert to produce optimal school performance. We conclude with a discussion on educational implications and future research to be addressed.     

Role of reading engagement in mediating effects of reading comprehension instruction on reading outcomes

The engagement model of reading development suggests that instruction improves students' reading comprehension to the extent that it increases students' engagement processes in reading. We compared how Concept‐Oriented Reading Instruction (CORI) (support for cognitive and motivational processes in reading), strategy instruction (support for cognitive strategies in reading), and traditional instruction in fourth‐grade classrooms differentially influenced students' reading comprehension, strategy use, and engagement in reading. Students experiencing CORI were significantly higher than both comparison groups on reading comprehension, reading strategies, and reading engagement. When students' level of reading engagement was statistically controlled, the differences between the treatment groups were not significant. We infer that the level of students' reading engagement during classroom work mediated the instructional effects on reading outcomes. © 2008 Wiley Periodicals, Inc.     

Disrupting the 'boys don't read' discourse: Primary school boys who love reading fiction

This article disrupts dominant discourses around boys and reading that often homogenise young males as reluctant, disengaged and, at times, adversarial readers. Rather than essentialising boys, we argue there is a need for a more sophisticated knowledge base about the influences, constraints and diverse experiences of boys as readers in society today. Drawing on interviews (n = 30) with Year 4 (8 to 9-year-old) boys at six schools, we consider their personal recounts of their enjoyment in reading, their preferred reading choices and narratives related to their experiences as readers at school. Analysis highlights boys' emerging reading interests, sophisticated and specific reading preferences, and changes in reading identities over time. Boys' preferences for particular fiction authors, novel series and genres dispute the common assumption in educational contexts that boys prefer to engage with non-fiction books. This finding is significant, as negative gendered stereotypes can impact on boys' reading self-concepts. It is also critical given Jerrim and Moss's recent research highlighting the importance of fiction in the development of reading skills. We consider implications for pedagogical practices that broaden reading experiences for the diversity of emerging masculine reading identities in nations such as Australia, where there is an absence of reading for pleasure in education policies.     

Exploring the Co‐Development of Reading Fluency and Reading Comprehension: A Twin Study

This study explores the co‐development of two related but separate reading skills, reading fluency and reading comprehension, across Grades 1–4. A bivariate biometric dual change score model was applied to longitudinal data collected from 1,784 twin pairs between the ages of 6 and 10 years. Grade 1 skills were influenced by highly overlapping genetic and environmental factors. Growth in both skills was influenced by highly overlapping shared environmental factors. Cross‐lagged parameters indicated bidirectional effects, with stronger effects from fluency to comprehension change than from comprehension to fluency change.     

Integrating Scenario‐Based and Component Reading Skill Measures to Understand the Reading Behavior of Struggling Readers

In recent years, researchers, educators, and policy makers have called for a new generation of reading comprehension assessments (e.g., Partnership for 21st Century Skills, 2008). Advocates of this movement argue for a deeper type of reading assessment, one that captures students’ ability to not only understand single texts in isolation but also to engage in purposeful, multisource integration of sources. While this shift in how we define and measure reading comprehension is laudable, assessments must also measure the fundamental reading skills that may impede higher‐level comprehension processes. This article presents data from two assessments that were designed to work in tandem to provide a more complete picture of reading comprehension. Middle school students were given a component skills battery which measured core reading skills such as word recognition, decoding, vocabulary, and morphology, as well a second assessment designed to measure reading comprehension. Reading comprehension was measured using a scenario‐based assessment approach, which required students to read a range of sources to fulfill a particular reading goal. The results indicate that students, including struggling readers, were able to read, understand, and problem solve in complex learning environments, but students’ ability to do so was often tempered by their basic reading skills. We argue that including a measure of component skills alongside a measure of higher‐level comprehension is beneficial in interpreting student performance. Accordingly, we present the results on the scenario‐based measure as a function of reading component skills and argue for the value of using this approach for struggling readers.     

Reading and spelling in adults: are there lexical and sub‐lexical subtypes?

The dual‐route model of reading proposes distinct lexical and sub‐lexical procedures for word reading and spelling. Lexically reliant and sub‐lexically reliant reader subgroups were selected from 78 university students on the basis of their performance on lexical (orthographic) and sub‐lexical (phonological) choice tests, and on irregular and nonword naming. In spelling of irregular words and nonwords to dictation, the group comparisons failed to support the dissociative predictions for lexical and sub‐lexical reliance that were derived from the dual‐route model: lexical readers were not superior to sub‐lexical readers on spelling irregular words as well as inferior to sub‐lexical readers on spelling regular letter strings (nonwords). In line with a single‐route view, print exposure and phonological coding (nonword naming accuracy) appear to be key factors in the effective learning of both regular and irregular words.     

Regularisation of nonwords in dyslexia: contributions of visual orthographic and phonological onsets

This study investigated the contributions of visual orthographic (analogy) and phonological processes in mediating nonword reading in children with dyslexia. Three groups of primary school age children (n=15 in each group) were recruited. The first group were children with dyslexia (mean age 11 years 3 months, mean reading age 8 years 3 months), the second group were chronological age controls (mean age 11 years 3 months, mean reading age 11 years 8 months) and the third group were reading age matched controls (mean age 7 years 11 months, mean reading age 8 years 3 months). All participants were required to read aloud a list of nonwords. Nonwords in the list were derived from paired regular and irregular keywords in which onsets were manipulated to be either phonologically or visually similar to keyword onsets. ANOVAs revealed firstly that children with dyslexia were the least likely to regularise nonword pronunciation and secondly, that all groups displayed an overall preference for words that were phonologically manipulated. These findings have been interpreted within the context of dual‐route theory.     

RESOLV: Readers' Representation of Reading Contexts and Tasks

We introduce RESOLV, a theoretical model to account for readers' construction and management of goals during text comprehension and use. RESOLV focuses on readers' experience of their physical, social, and communicative context prior to actually engaging with texts. RESOLV assumes that readers construct two types of mental models prior to reading: The context model is a representation of the physical and social reading context, whereas the task model is a set of goals and plans that drives readers' decisions and actions in reading. We first present the RESOLV model, and we articulate two core hypotheses. We then present and discuss evidence supporting these hypotheses, from past and more recent research conducted in our labs, as well as in others'. The data support the view that reading decisions and processes are guided by readers' perceptions and attributions regarding the task statement but also more implicit cues from the reading context.     

Word Reading Fluency: Role of Genome‐Wide Single‐Nucleotide Polymorphisms in Developmental Stability and Correlations With Print Exposure

The genetic effects on individual differences in reading development were examined using genome‐wide complex trait analysis (GCTA) in a twin sample. In unrelated individuals (one twin per pair, n = 2,942), the GCTA‐based heritability of reading fluency was ~20%–29% at ages 7 and 12. GCTA bivariate results showed that the phenotypic stability of reading fluency from 7 to 12 years (r = 0.69) is largely driven by genetic stability (genetic r = 0.69). Genetic effects on print exposure at age 12 were moderate (~26%) and correlated with those influencing reading fluency at 12 (genetic r = 0.89), indicative of a gene–environment correlation. These findings were largely consistent with quantitative genetic twin analyses that used both twins in each pair (n = 1,066–1,409).