Predicting Later Spelling from Kindergarten Spelling in U.S., Australian, and Swedish Children.

Purpose: Using data from 1,868 children from the US, Australia, and Sweden who took a 10-word spelling test in kindergarten and a standardized spelling test in Grades 1, 2, and (except for the Australian children) Grade 4, we examined two questions. First, does the quality of a child's errors on the kindergarten test help predict later spelling performance even after controlling for the number of correct responses on the kindergarten test? Second, does spelling develop at a faster pace in Swedish than in English? Method: We measured kindergarten error quality based on the number of letter additions, deletions, and substitutions needed to transform each error into the correct spelling. Using mixed-model analyses, we examined the relationship of this and other variables to later spelling performance. Results: Kindergarten error quality contributed significantly to the prediction of later spelling performance even after consideration of the number of correct spellings in kindergarten and other relevant variables. The Swedish children showed more rapid growth in spelling than the U.S. and Australian children, a difference that may reflect the greater transparency of spelling-to-sound links in Swedish. Conclusion: Information from a spelling test that is typically discarded-information about the nature of the errors-has value.

Addressing genetic essentialism: Sharpening context in behavior genetics.

Evidence of a causal role for genes in human behavior underpins genetic essentialism, the scientifically flawed and socially hazardous idea that heritable characteristics are immutable. Behavior geneticists can challenge this idea by designing research that brings the contextual dependence of heritability estimates into sharper focus, and by incorporating a relevant statement into research reports and public outreach.

Mathematics Difficulties and Psychopathology in School-Age Children.

This study investigated the relationship between mathematics difficulties and psychopathology in a large community sample (N = 881) of youth (8-18 years of age) in the United States. The primary aims of the study were to (a) test the associations between mathematics difficulties and specific components of internalizing, externalizing, attention, and social problems; (b) examine potential age and gender differences; and (c) investigate the longitudinal relationship between mathematics and psychopathology using 5-year follow-up data. Results indicated that individuals with mathematics difficulties exhibited elevations in most dimensions of psychopathology, including anxiety, depression, externalizing behaviors, attention problems, and social problems. Furthermore, mathematics impairment was associated with internalizing problems, rule-breaking behaviors, inattention, and social problems even after controlling for comorbid reading difficulties. Results suggested that the associations between mathematics and psychopathology are generally similar in males and females. Finally, preliminary longitudinal evidence suggested that initial mathematics difficulties predicted elevations of conduct disorder, rule-breaking behavior, inattention, hyperactivity, and social problems at follow-up, with several of these associations remaining significant even after controlling for initial reading. In contrast, there was no significant association between initial mathematics ability and internalizing symptoms at follow-up, demonstrating some amelioration of internalizing symptoms over time.

Discovery of 42 genome-wide significant loci associated with dyslexia.

Reading and writing are crucial life skills but roughly one in ten children are affected by dyslexia, which can persist into adulthood. Family studies of dyslexia suggest heritability up to 70%, yet few convincing genetic markers have been found. Here we performed a genome-wide association study of 51,800 adults self-reporting a dyslexia diagnosis and 1,087,070 controls and identified 42 independent genome-wide significant loci: 15 in genes linked to cognitive ability/educational attainment, and 27 new and potentially more specific to dyslexia. We validated 23 loci (13 new) in independent cohorts of Chinese and European ancestry. Genetic etiology of dyslexia was similar between sexes, and genetic covariance with many traits was found, including ambidexterity, but not neuroanatomical measures of language-related circuitry. Dyslexia polygenic scores explained up to 6% of variance in reading traits, and might in future contribute to earlier identification and remediation of dyslexia.

Modeling the Speeded Determinants of Adolescents' Academic and Attentional Functioning.

The current study utilized a large, unselected sample of adolescent twins to examine whether processing speed (PS) is an important shared predictor that accounts for covariance among reading, math, ADHD, and rapid naming (RN). The best fitting model included correlated but distinguishable latent measures of PS, RN, reading, math, inattention, hyperactivity/impulsivity, and academic fluency. PS was a shared predictor across all outcomes, while RN was uniquely associated with reading, fluency, and (albeit weakly) math. The results add to a growing literature suggesting that PS and RN may be important components of comprehensive neuropsychological models of academics, ADHD, and their covariation.

In Search of Cognitive Promotive and Protective Factors for Word Reading.

This study examined whether strong cognitive skills (i.e. vocabulary, rapid naming, verbal working memory [VWM], and processing speed [PS]) contributed to resilience in single-word reading skills in children at risk for reading difficulties because of low phonological awareness scores (PA). Promotive factors were identified by main effects and protective factors through PA x cognition interactions. This study included 1,807 children ages 8-16. As predicted, all cognitive skills were significantly related to reading, consistent with promotive effects. A significant, but small effect PA x vocabulary interaction (R2 change=.002, p=.00038) was detected but its form was not consistent with a classic protective effect. Rather, the PA x vocabulary interaction was consistent with a "skill-enhancement" pattern, such that children with strong PA and vocabulary skills had better than expected reading. This study provides a framework for reading resilience research and directs attention to promotive mechanisms underlying reading success.

How Specific Are Learning Disabilities?

Despite historical emphasis on "specific" learning disabilities (SLDs), academic skills are strongly correlated across the curriculum. Thus, one can ask how specific SLDs truly are. To answer this question, we used bifactor models to identify variance shared across academic domains (academic g), as well as variance unique to reading, mathematics, and writing. Participants were 686 children ages 8 to 16. Although the sample was overselected for learning disabilities, we intentionally included children across the full range of individual differences in this study in response to growing recognition that a dimensional, quantitative view of SLD is more accurate than a categorical view. Confirmatory factor analysis identified five academic domains (basic reading, reading comprehension, basic math, math problem-solving, and written expression); spelling clustered with basic reading and not writing. In the bifactor model, all measures loaded significantly on academic g. Basic reading and mathematics maintained variance distinct from academic g, consistent with the notion of SLDs in these domains. Writing did not maintain specific variance apart from academic g, and evidence for reading comprehension-specific variance was mixed. Academic g was strongly correlated with cognitive g (r = .72) but not identical to it. Implications for SLD diagnosis are discussed.

Genome-wide association study reveals new insights into the heritability and genetic correlates of developmental dyslexia.

Developmental dyslexia (DD) is a learning disorder affecting the ability to read, with a heritability of 40-60%. A notable part of this heritability remains unexplained, and large genetic studies are warranted to identify new susceptibility genes and clarify the genetic bases of dyslexia. We carried out a genome-wide association study (GWAS) on 2274 dyslexia cases and 6272 controls, testing associations at the single variant, gene, and pathway level, and estimating heritability using single-nucleotide polymorphism (SNP) data. We also calculated polygenic scores (PGSs) based on large-scale GWAS data for different neuropsychiatric disorders and cortical brain measures, educational attainment, and fluid intelligence, testing them for association with dyslexia status in our sample. We observed statistically significant (p < 2.8 × 10-6) enrichment of associations at the gene level, for LOC388780 (20p13; uncharacterized gene), and for VEPH1 (3q25), a gene implicated in brain development. We estimated an SNP-based heritability of 20-25% for DD, and observed significant associations of dyslexia risk with PGSs for attention deficit hyperactivity disorder (at pT = 0.05 in the training GWAS: OR = 1.23[1.16; 1.30] per standard deviation increase; p = 8 × 10-13), bipolar disorder (1.53[1.44; 1.63]; p = 1 × 10-43), schizophrenia (1.36[1.28; 1.45]; p = 4 × 10-22), psychiatric cross-disorder susceptibility (1.23[1.16; 1.30]; p = 3 × 10-12), cortical thickness of the transverse temporal gyrus (0.90[0.86; 0.96]; p = 5 × 10-4), educational attainment (0.86[0.82; 0.91]; p = 2 × 10-7), and intelligence (0.72[0.68; 0.76]; p = 9 × 10-29). This study suggests an important contribution of common genetic variants to dyslexia risk, and novel genomic overlaps with psychiatric conditions like bipolar disorder, schizophrenia, and cross-disorder susceptibility. Moreover, it revealed the presence of shared genetic foundations with a neural correlate previously implicated in dyslexia by neuroimaging evidence.

Exploring the Influence of Early Childhood Education and Care on the Etiology of Achievement.

The present study used a genetically-sensitive quantile regression approach to examine the relation between participation in early childhood education and care (ECEC) and subsequent school performance in literacy and numeracy at grades 3, 5, 7, and 9. The sample consisted of 1255 twin pairs (596 MZ; 659 DZ) with information on both ECEC and the National Assessment Program-Literacy and Numeracy (NAPLAN) scores from the Twin Study of NAPLAN. Results indicated variation in heritability estimates across the distributions of achievement, suggesting that different patterns of etiological influences may exist among children of different ability levels. Additionally, the results provided no evidence that ECEC significantly influenced achievement, and in the genetically-sensitive analyses, no evidence that ECEC moderated the influences of heritability of achievement for typically advantaged children. These results suggest that ECEC may not provide the levels of environmental support for later achievement that advocates claim, although we acknowledge that ECEC quality, which was not measured in the current study, may make a difference in whether or not ECEC influences achievement.

Using an item-specific predictor to test the dimensionality of the orthographic choice task.

The orthographic choice (OC) task-requiring individuals to choose the correct spelling between a word and a pseudohomophone foil (e.g., goat vs. gote)-has been used as an outcome measure of orthographic learning and as a predictor of individual differences in word reading development. Some consider the OC task a measure of orthographic knowledge (e.g., Conrad, Harris, & Williams (Reading and Writing, 26(8), 1223-1239, 2013)), whereas others have suggested that the task measures a reader's familiarity with the word's orthographic representation and thus measures word reading skill (e.g., Castles & Nation, 2006). We examined this assertion by testing OC task performance of individuals ages 8 to 18 (J = 296) and their ability to read the OC target words (I = 80) in isolation using crossed random effects item-response models. Results reveal that response on the OC task is not fully determined by the ability of an individual to read the target word in isolation. Specifically, the probability of choosing the correct orthographic form when the word was pronounced incorrectly was .79; whereas it was .90 when the word was pronounced correctly. Measures of receptive spelling and phonemic awareness (person-characteristics) and word frequency and orthographic neighborhood size (item-characteristics) accounted for significant variance in orthographic choice after controlling for target item reading and other reading-related abilities. We interpret the results to suggest that the OC task taps both item-specific orthographic knowledge and more general orthographic knowledge.

The Academic Development Study of Australian Twins (ADSAT): Research Aims and Design.

The Academic Development Study of Australian Twins was established in 2012 with the purpose of investigating the relative influence of genes and environments in literacy and numeracy capabilities across two primary and two secondary school grades in Australia. It is the first longitudinal twin project of its kind in Australia and comprises a sample of 2762 twin pairs, 40 triplet sets and 1485 nontwin siblings. Measures include standardized literacy and numeracy test data collected at Grades 3, 5, 7 and 9 as part of the National Assessment Program: Literacy and Numeracy. A range of demographic and behavioral data was also collected, some at multiple longitudinal time points. This article outlines the background and rationale for the study and provides an overview for the research design, sample and measures collected. Findings emerging from the project and future directions are discussed.

Comment on Asbury and Wai (2019), "Viewing education policy through a genetic lens," Journal of School Choice.

Asbury and Wai (Journal of School Choice, 2019) perform a valuable service by summarizing much available behavior--genetic research on academic achievement. However they consider that no specific policies stem from the research body at this time. Here we do propose a policy based on some of our research using twins, namely that available funding for students struggling with learning to read be targeted to them individually rather than allocated to schools per se. We briefly canvass some practical issues, such as the variety of funding mechanisms, best-practice intervention techniques, and identification of struggling readers. We also outline a general research strategy for uncovering factors contributing to educational attainment that takes behavior-genetic research as its starting point and drills down from there, and advocate including genetically-sensitive methods in a growing list of quantitative research techniques in education.

Differential Influences of Genes and Environment Across the Distribution of Reading Ability.

We partitioned early childhood reading into genetic and environmental sources of variance and examined the full distribution of ability levels from low through normal to high as computed by quantile regression. The full sample comprised twin pairs measured at preschool (n = 977), kindergarten (n = 1028), grade 1 (n = 999), and grade 2 (n = 1000). Quantile regression analyses of the full distribution of literacy ability showed genetic influence in all grades from preschool to grade 2. At preschool, the low end of the distribution had higher genetic influence than the high end of the distribution and the shared environment influence was the opposite. These shared environment influences of preschool became insignificant with formal schooling. This suggests that higher scores in pre-literacy skills (preschool) are more influenced by shared environment factors, though these are short-lived. This study discusses the factors that may be influencing the results.

Cross-Country Differences in Parental Reporting of Symptoms of ADHD.

Previous studies within the United States suggest there are cultural and contextual influences on how Attention-Deficit/Hyperactivity Disorder (ADHD) symptoms are perceived. If such influences operate within a single country, they are likely to also occur between countries. In the current study, we tested whether country differences in mean ADHD scores also reflect cultural and contextual differences, as opposed to actual etiological differences. The sample for the present study included 974 participants from four countries tested at two-time points, the end of preschool and the end of 2nd grade. Consistent with previous research, we found lower mean ADHD scores in Norway and Sweden in comparison to Australia and the United States, and we tested four explanations for these country differences: 1) Genuine etiological differences, 2) Slower introduction to formal academic skills in Norway and Sweden than in the United States and Australia that indicated a context difference, 3) Under-reporting tendency in Norway and Sweden, or 4) Over-reporting tendency in the United States and Australia. Either under-or over-reporting would be examples of cultural differences in the perception of ADHD symptoms. Of these explanations, results of ADHD measurement equivalence tests across countries rejected the first three explanations and supported the fourth explanation: an over-reporting tendency in the United States and Australia. These findings indicate that parental reporting of ADHD symptoms is more accurate in Norway and Sweden than in Australia and the United States, and thus have important clinical and educational implications for how parental reporting informs an ADHD diagnosis in these countries.

Understanding Comorbidity Between Specific Learning Disabilities.

Current definitions of specific learning disability (SLD) identify a heterogeneous population that includes individuals with weaknesses in reading, math, or writing, and these academic difficulties often co-occur in many of the same individuals. The Colorado Learning Disabilities Research Center (CLDRC) is an interdisciplinary, multisite research program that uses converging levels of analysis to understand the genetic and environmental etiology, neuropsychology, and developmental outcomes of SLDs in reading (RD), math (MD), and writing (WD), along with the comorbidity between these SLDs and other developmental disorders. The latest results from the CLDRC twin study suggest that shared genetic influences contribute to the significant covariance between all aspects of reading (word reading, reading fluency, and reading comprehension) and math (calculations, math fluency, and word problems), and distinct genetic or environmental influences also contribute to weaknesses in each specific academic domain. RD and MD are associated with a range of negative outcomes on both concurrent measures and measures of functional outcomes completed 5 years after the twins were first assessed. Over the next several years the CLDRC will continue to expand on this work by administering a comprehensive test battery that includes measures of all dimensions of academic achievement that are described in current definitions of SLD and incorporating these measures in new neuroimaging and molecular genetic studies.

Multivariate genome-wide association study of rapid automatised naming and rapid alternating stimulus in Hispanic American and African-American youth.

BACKGROUND: Rapid automatised naming (RAN) and rapid alternating stimulus (RAS) are reliable predictors of reading disability. The underlying biology of reading disability is poorly understood. However, the high correlation among RAN, RAS and reading could be attributable to shared genetic factors that contribute to common biological mechanisms. OBJECTIVE: To identify shared genetic factors that contribute to RAN and RAS performance using a multivariate approach. METHODS: We conducted a multivariate genome-wide association analysis of RAN Objects, RAN Letters and RAS Letters/Numbers in a sample of 1331 Hispanic American and African-American youth. Follow-up neuroimaging genetic analysis of cortical regions associated with reading ability in an independent sample and epigenetic examination of extant data predicting tissue-specific functionality in the brain were also conducted. RESULTS: Genome-wide significant effects were observed at rs1555839 (p=4.03×10-8) and replicated in an independent sample of 318 children of European ancestry. Epigenetic analysis and chromatin state models of the implicated 70 kb region of 10q23.31 support active transcription of the gene RNLS in the brain, which encodes a catecholamine metabolising protein. Chromatin contact maps of adult hippocampal tissue indicate a potential enhancer-promoter interaction regulating RNLS expression. Neuroimaging genetic analysis in an independent, multiethnic sample (n=690) showed that rs1555839 is associated with structural variation in the right inferior parietal lobule. CONCLUSION: This study provides support for a novel trait locus at chromosome 10q23.31 and proposes a potential gene-brain-behaviour relationship for targeted future functional analysis to understand underlying biological mechanisms for reading disability.

Genome-wide association scan identifies new variants associated with a cognitive predictor of dyslexia.

Developmental dyslexia (DD) is one of the most prevalent learning disorders, with high impact on school and psychosocial development and high comorbidity with conditions like attention-deficit hyperactivity disorder (ADHD), depression, and anxiety. DD is characterized by deficits in different cognitive skills, including word reading, spelling, rapid naming, and phonology. To investigate the genetic basis of DD, we conducted a genome-wide association study (GWAS) of these skills within one of the largest studies available, including nine cohorts of reading-impaired and typically developing children of European ancestry (N = 2562-3468). We observed a genome-wide significant effect (p < 1 × 10-8) on rapid automatized naming of letters (RANlet) for variants on 18q12.2, within MIR924HG (micro-RNA 924 host gene; rs17663182 p = 4.73 × 10-9), and a suggestive association on 8q12.3 within NKAIN3 (encoding a cation transporter; rs16928927, p = 2.25 × 10-8). rs17663182 (18q12.2) also showed genome-wide significant multivariate associations with RAN measures (p = 1.15 × 10-8) and with all the cognitive traits tested (p = 3.07 × 10-8), suggesting (relational) pleiotropic effects of this variant. A polygenic risk score (PRS) analysis revealed significant genetic overlaps of some of the DD-related traits with educational attainment (EDUyears) and ADHD. Reading and spelling abilities were positively associated with EDUyears (p ~ [10-5-10-7]) and negatively associated with ADHD PRS (p ~ [10-8-10-17]). This corroborates a long-standing hypothesis on the partly shared genetic etiology of DD and ADHD, at the genome-wide level. Our findings suggest new candidate DD susceptibility genes and provide new insights into the genetics of dyslexia and its comorbities.

Invariance of ADHD Symptoms Across Sex and Age: a Latent Analysis of ADHD and Impairment Ratings from Early Childhood into Adolescence.

A population-based longitudinal sample of 489 twin pairs was assessed at six time points over ten years to examine the measurement invariance and stability of attention-deficit/hyperactivity disorder (ADHD) symptoms, as well as the developmental relations between inattention (IN), hyperactivity-impulsivity (HI), and multiple aspects of functional impairment. Parent ratings of ADHD symptoms and functional impairment were obtained in preschool and after the completion of kindergarten, first, second, fourth, and ninth grades. Results of the temporal and sex invariance models indicated that parent ratings of the 18 ADHD symptoms function in the same manner for females and males from early childhood into adolescence. In addition to establishing this prerequisite condition for the interpretation of longitudinal and between-sex differences in the IN and HI symptom dimensions, cross-lagged models indicated that both IN and HI were associated with increased risk for both concurrent and future overall, social, and recreational impairment, whereas only IN was uniquely associated with later academic impairment. Taken together, the current results demonstrate that IN and HI are highly stable from preschool through ninth grade, invariant between females and males, and indicative of risk for impairment in multiple areas, thereby providing strong support for the validity of the symptom dimensions among both sexes.

Little Evidence That Socioeconomic Status Modifies Heritability of Literacy and Numeracy in Australia.

Socioeconomic status (SES) has been found to moderate the influence of genes and the environment on cognitive ability, such that genetic influence is greater when SES is higher, and the shared environment is greater when SES is lower, but not in all Western countries. The effects of both family and school SES on the heritability of literacy and numeracy in Australian twins aged 8, 10, 12, and 14 years with 1,307, 1,235, 1,076, and 930 pairs at each age, respectively, were tested. Shared environmental influences on Grade 3 literacy were greater with low family SES, and no other moderating effects of SES were significant. These findings are contrasted with results from the United States and the United Kingdom.