Genetic and environmental influences on prereading skills and early reading and spelling development in the United States, Australia, and Scandinavia

Genetic and environmental influences on prereading skills in preschool and on early reading and spelling development at the end of kindergarten were compared among samples of identical and fraternal twins from the U.S. (Colorado), Australia, and Scandinavia. Mean comparisons revealed significantly lower preschool print knowledge in Scandinavia, consistent with the relatively lower amount of shared book reading and letter-based activities with parents, and lack of emphasis on print knowledge in Scandinavian preschools. The patterns of correlations between all preschool environment measures and prereading skills within the samples were remarkably similar, as were the patterns of genetic, shared environment, and non-shared environment estimates: in all samples, genetic influence was substantial and shared environment influence was relatively weak for phonological awareness, rapid naming, and verbal memory; genetic influence was weak, and shared environment influence was relatively strong for vocabulary and print knowledge. In contrast, for reading and spelling assessed at the end of kindergarten in the Australian and U.S. samples, there was some preliminary evidence for country differences in the magnitude of genetic and environmental influences. We argue that the apparently higher genetic and lower shared environment influence in the Australian sample was related to a greater emphasis on formal reading instruction, resulting in more advanced reading and spelling skills at the end of kindergarten, and thus there was greater opportunity to observe genetic influences on response to systematic reading instruction among the Australian twins.     

The relations of early phonological awareness,rapid‐naming and speed of processing with the development of spelling and reading: a longitudinal examination

Phonological awareness has been found to be strongly related to spelling. Findings on the relations between rapid‐naming and spelling are less consistent and have been suggested to be shared with speed of processing. This study set out to examine these relations in spelling and reading of Hebrew. Children attending the regular educational system were followed longitudinally (N = 70): phonological awareness, rapid‐naming and speed of processing were tested in kindergarten and in grade 1, and spelling and reading were tested in grade 2. Kindergarten and grade 1 rapid‐naming predicted spelling and word reading, and grade 1 phonological awareness predicted spelling, word reading and decoding. Speed of processing was an insignificant predictor. The findings extend the role of phonological awareness in spelling to an orthography with partial phonological representations and concurrently suggest weak relations. The results further suggest a link between rapid‐naming and orthographic knowledge, which may not be explained by shared variance with speed of processing.     

Developmental Relations Between Vocabulary Knowledge and Reading Comprehension: A Latent Change Score Modeling Study

The present study followed a sample of first‐grade (N = 316, M_age = 7.05 at first test) through fourth‐grade students to evaluate dynamic developmental relations between vocabulary knowledge and reading comprehension. Using latent change score modeling, competing models were fit to the repeated measurements of vocabulary knowledge and reading comprehension to test for the presence of leading and lagging influences. Univariate models indicated growth in vocabulary knowledge, and reading comprehension was determined by two parts: constant yearly change and change proportional to the previous level of the variable. Bivariate models indicated previous levels of vocabulary knowledge acted as leading indicators of reading comprehension growth, but the reverse relation was not found. Implications for theories of developmental relations between vocabulary and reading comprehension are discussed.     

Unraveling the Relation Between Reading Comprehension and Print Exposure

The purpose of this study was to test the directionality of influence between reading comprehension (RC) and print exposure (PE), thereby estimating genetic and environmental effects of this relation. The sample consisted of 910 twins in fourth through ninth grades (M_age = 12.33 years, SD = 1.41) from the Florida Twin Project on Reading, Behavior, and Environment. Using direction-of-causation model in a twin design, results supported a direction of influence running from RC to PE. This relation was underpinned by genetic and environmental factors of RC as well as PE. Implications for reading education are discussed.     

Early Literacy Predictors and Second-Grade Outcomes in Children Who Are Hard of Hearing

This study contrasted the early literacy outcomes of children who are hard of hearing (CHH) with children with normal hearing (CNH). At age 5, prereading skills of oral language, phonological processing, and print knowledge were examined in CHH (N = 180) and CNH (N = 80). The CHH had poorer oral language and phonological processing abilities than the CNH but comparable knowledge of print. At age 8, measures of word reading, and reading comprehension yielded no differences between CHH (N = 108) and CNH (N = 62) except for reading comprehension for the moderately severe CHH. Reading achievement in CHH was found to exceed predictions based on prereading performance. This resilience was associated with gains in oral language during the early school years.     

Evidence for Common Etiological Influences on Early Literacy Skills in Kindergarten

Understanding how the etiology of print awareness and phonological awareness are related to the etiology of decoding can provide insights into the development of word reading. To address this issue, we examined the degree of overlap among etiological influences of prereading skills in 1,252 twin pairs in kindergarten. Genetic, shared environmental, and nonshared environmental factors were significant for all three literacy phenotypes. The majority of genetic and shared environmental influence on decoding was due to common factors that included print awareness and phonological awareness. Notably, only a single genetic factor contributed to all three literacy phenotypes, but there was additional shared environmental influence common to phonological awareness and decoding. Findings suggest commonalities in the etiology of prereading literacy skills that could inform work on the development of reading skill.     

Genetic and environmental influences on early literacy

Prereading and early reading skills of preschool twin children in Australia, Scandinavia and the United States were explored in a genetically sensitive design (max. N=627 preschool pairs and 422 kindergarten pairs). Analyses indicated a strong genetic influence on preschool phonological awareness, rapid naming and verbal memory. Print awareness, vocabulary and grammar/morphology were subject primarily to shared environment effects. There were significant genetic and shared environment correlations among the preschool traits. Kindergarten reading, phonological awareness and rapid naming were primarily affected by genes, and spelling was equally affected by genes and shared environment. Multivariate analyses revealed genetic and environmental overlap and independence among kindergarten variables. Longitudinal analyses showed genetic continuity as well as change in phonological awareness and rapid naming across the 2 years. Relations among the preschool variables of print awareness, phonological awareness and rapid naming and kindergarten reading were also explored in longitudinal analyses. Educational implications are discussed.     

Language and Cognitive Predictors of Text Comprehension: Evidence From Multivariate Analysis

Using data from children in South Korea (N = 145, M_age = 6.08), it was determined how low‐level language and cognitive skills (vocabulary, syntactic knowledge, and working memory) and high‐level cognitive skills (comprehension monitoring and theory of mind [ToM]) are related to listening comprehension and whether listening comprehension and word reading mediate the relations of language and cognitive skills to reading comprehension. Low‐level skills predicted comprehension monitoring and ToM, which in turn predicted listening comprehension. Vocabulary and syntactic knowledge were also directly related to listening comprehension, whereas working memory was indirectly related via comprehension monitoring and ToM. Listening comprehension and word reading completely mediated the relations of language and cognitive skills to reading comprehension.     

Longitudinal twin study of early reading development in three countries: Preliminary results

We have initiated parallel longitudinal studies in Australia (Byrne, PI), the United States (Olson, PI), and Norway (Samuelsson, PI) of identical and fraternal twins who are being tested in preschool for prereading skills, and in kindergarten, first grade, and second grade for the development of early reading, spelling, and related cognitive skills. Comparisons of the similarities of identical and fraternal twins will reveal the relative influence of genetic, shared family environment, and nonshared environment on individual differences at and across different stages of development. Family and twin-specific environmental information is also being directly assessed through parent questionnaires and observations by testers. Most of the data collected so far have been from preschool twins (146 in Australia, 284 in the United States, and 70 in Norway). Preliminary analyses for the preschool cognitive measures showed reliable genetic influences on phonological awareness and several measures of memory and learning. In contrast, vocabulary, grammar, and morphology showed significant shared environment and negligible genetic effects. A print knowledge composite showed both genetic and shared environment influence.     

Cognitive Attributes,Attention, and Self‐Efficacy of Adequate and Inadequate Responders in a Fourth Grade Reading Intervention

We examined cognitive attributes, attention, and self‐efficacy of fourth grade struggling readers who were identified as adequate responders (n = 27), inadequate responders with comprehension only deficits (n = 46), and inadequate responders with comprehension and word reading deficits (n = 52) after receiving a multicomponent reading intervention. We also included typical readers (n = 40). These four groups were compared on measures of nonverbal reasoning, working memory, verbal knowledge, listening comprehension, phonological awareness, and rapid naming as well as on teacher ratings of attention problems and self‐reported self‐efficacy. The two inadequate responder groups demonstrated difficulties primarily with verbal knowledge and listening comprehension compared to typical readers and adequate responders. Phonological awareness and rapid naming differentiated the two inadequate responder groups. In addition, both inadequate responder groups showed more attention problems and low self‐efficacy compared to typical readers.     

Concurrent and Longitudinal Contributions of a Brief Assessment of Reading‐Specific Executive Function to Reading Comprehension in First and Second Grade Students

Executive function (EF) contributes significantly to reading comprehension across the lifespan. Emerging research indicates domain‐specific assessments of EF are better suited for assessment and intervention in academic contexts. For example, graphophonological‐semantic cognitive flexibility (GSF), the ability to flexibly switch between the graphophonological and semantic components of printed words, contributes uniquely to reading comprehension across the lifespan, and GSF training improves children's reading comprehension. This study compared the original GSF measure, which is problematic for use in schools due to its subjectively interpreted explicit explanation component, to an abbreviated implicit task that is better suited for assessment of GSF in practical contexts in 68 first and second grade students. Implicit and explicit GSF contributed uniquely to reading comprehension concurrently and longitudinally when children (n = 31) were in third and fourth grades, beyond verbal ability, decoding ability, and matrix reasoning.     

Simple but complex: components of the simple view of reading across grade levels

The purpose of this study was to examine the simple view of reading (SVR) and contributions of verbal proficiency and reading fluency to reading comprehension for fourth‐, seventh‐ and ninth‐grade readers (N=271). The SVR explained a significant proportion of variance in reading comprehension for all grades with decreasing explained variance in higher grades. The variance explained by decoding decreased from fourth grade to higher grades. The variance explained by listening comprehension increased from fourth‐ to seventh‐grade, but did not change from seventh‐ to ninth‐grade. In all grades, verbal proficiency and reading fluency contributed substantial additional variance to reading comprehension beyond the SVR. Changes in the predictive relation between listening and reading comprehension and factors influencing reading comprehension in each grade are discussed.     

Does IQ matter in adolescents' reading disability?

We studied the connection of IQ, reading disability (RD) and their interaction with reading, spelling and other cognitive skills in adolescents with average IQ and RD (n = 22), average IQ, non-RD (n = 71), below average IQ and RD (n = 29), and below average IQ non-RD (n = 33). IQ was not connected to reading and spelling in subjects without RD, but a connection to non-word spelling in subjects with RD existed. IQ and RD showed a connection to other cognitive skills (IQ to working memory, verbal memory and syntactic skills, RD to poor performance in text reading and rapid naming and both of them to reading comprehension, phonological and arithmetic skills), but no interaction existed. Our results are consistent with those of earlier studies showing that IQ does not play a significant role in the presentation of RD. However, adolescents with below average IQ and RD seemed to have much broader deficits in academically important skills such as arithmetic and reading comprehension than the other groups.     

Unpicking the Developmental Relationship Between Oral Language Skills and Reading Comprehension: It's Simple,But Complex

Listening comprehension and word decoding are the two major determinants of the development of reading comprehension. The relative importance of different language skills for the development of listening and reading comprehension remains unclear. In this 5‐year longitudinal study, starting at age 7.5 years (n = 198), it was found that the shared variance between vocabulary, grammar, verbal working memory, and inference skills was a powerful longitudinal predictor of variations in both listening and reading comprehension. In line with the simple view of reading, listening comprehension, and word decoding, together with their interaction and curvilinear effects, explains almost all (96%) variation in early reading comprehension skills. Additionally, listening comprehension was a predictor of both the early and later growth of reading comprehension skills.     

Genetic and environmental influences on writing and their relations to language and reading

Identical and fraternal twins (N?=?540, age 8 to 18 years) were tested on three different measures of writing (Woodcock-Johnson III Tests of Achievement—Writing Samples and Writing Fluency; Handwriting Copy from the Group Diagnostic Reading and Aptitude Achievement Tests), three different language skills (phonological awareness, rapid naming, and vocabulary), and three different reading skills (word recognition, spelling, and reading comprehension). Substantial genetic influence was found on two of the writing measures, writing samples and handwriting copy, and all of the language and reading measures. Shared environment influences were generally not significant, except for Vocabulary. Non-shared environment estimates, including measurement error, were significant for all variables. Genetic influences among the writing measures were significantly correlated (highest between the speeded measures writing fluency and handwriting copy), but there were also significant independent genetic influences between copy and samples and between fluency and samples. Genetic influences on writing were significantly correlated with genetic influences on all of the language and reading skills, but significant independent genetic influences were also found for copy and samples, whose genetic correlations were significantly less than 1.0 with the reading and language skills. The genetic correlations varied significantly in strength depending on the overlap between the writing, language, and reading task demands. We discuss implications of our results for education, limitations of the study, and new directions for research on writing and its relations to language and reading.     

Modeling the Etiology of Individual Differences in Early Reading Development: Evidence for Strong Genetic Influences

We explored the etiology of individual differences in reading development from post-kindergarten to post–4th grade by analyzing data from 487 twin pairs tested in Colorado. Data from three reading measures and one spelling measure were fit to biometric latent growth curve models, allowing us to extend previous behavioral genetic studies of the etiology of early reading development at specific time points. We found primarily genetic influences on individual differences at post–1st grade for all measures. Genetic influences on variance in growth rates were also found, with evidence of small, nonsignificant, shared environmental influences for two measures. We discuss our results, including their implications for educational policy.     

The Relationship of Spelling Recognition, RAN, and Phonological Awareness to Reading Skills in Older Poor Readers and Younger Reading-Matched Controls

The role of spelling recognition was examined in word reading skills and reading comprehension for dyslexic and nondyslexic children. Dyslexic and nondyslexic children were matched on their raw word reading proficiency. Relationships between spelling recognition and the following were examined for both groups of children: verbal ability, working memory, phonological measures, rapid naming, word reading, and reading comprehension. Children’s performance in spelling recognition was significantly associated with their skills in word reading and reading comprehension regardless of their reading disability status. Furthermore, spelling recognition contributed significant variance to reading comprehension for both dyslexic and nondyslexic children after the effects of phonological awareness, rapid naming, and word reading proficiency had been accounted for. The results support the role of spelling recognition in reading development for both groups of children and they are discussed using a componential reading fluency framework.     

Preschool cognitive and language skills predicting Kindergarten and Grade 1 reading and spelling: a cross‐linguistic comparison

The importance of cognitive and language skills on reading and spelling development were investigated in a cross‐linguistic longitudinal study of 737 English‐speaking children (US/Australia) and 169 Scandinavian children (Norway/Sweden) from preschool to Kindergarten and Grade 1. The results revealed that phonological awareness and print knowledge were the strongest predictors of early reading and spelling across orthographies. The contribution from rapid naming to literacy development was low in Kindergarten, but similar to that of phonological awareness and print knowledge in Grade 1. The present study identified a significant difference across orthographies in the effects of print knowledge and general verbal ability on spelling in Kindergarten. However, this pattern was explained by cultural rather than orthographic differences. The results indicate that cognitive and language skills underlying early reading and spelling development are similar across alphabetic orthographies.     

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).     

Correlates of early reading performance in a transparent orthography

A cross-sectional study was conducted with 83first – and 81 fourth graders at the end of theschool year to examine factors accounting forearly reading performance in Finnish, atransparent orthography with a clear mapping ofphonemes onto graphemes. Measures for bothgrades included reading comprehension, phonemeawareness, and object- and digit naming.Additionally measures of skills in morphology,spelling and a screening battery wereadministered to the first graders. The sets ofmeasures accounted for 56% of the variance inreading performance in first grade and 64% infourth grade. Phoneme awareness was stronglyrelated to reading performance and spelling atthe end of first grade, but only forless-skilled readers in fourth grade. Theseresults suggest a larger role for phonemeawareness for children learning a transparentorthography than has been suggested in earlierstudies. At the same time, listeningcomprehension contributed more strongly tofirst-grade reading performance than has beenreported for children learning to readEnglish.