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.

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.

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.

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.

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.

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.

Literacy acquisition influences children's rapid automatized naming.

Previous research has established that learning to read improves children's performance on reading-related phonological tasks, including phoneme awareness (PA) and nonword repetition. Few studies have investigated whether literacy acquisition also promotes children's rapid automatized naming (RAN). We tested the hypothesis that literacy acquisition should influence RAN in an international, longitudinal population sample of twins. Cross-lagged path models evaluated the relationships among literacy, PA, and RAN across four time points from pre-kindergarten through grade 4. Consistent with previous research, literacy showed bidirectional relationships with reading-related oral language skills. We found novel evidence for an effect of earlier literacy on later RAN, which was most evident in children at early phases of literacy development. In contrast, the influence of earlier RAN on later literacy was predominant among older children. These findings imply that the association between these two related skills is moderated by development. Implications for models of reading development and for dyslexia research are discussed.

Associations between selected dietary behaviours and academic achievement: A study of Australian school aged children.

BACKGROUND: Research investigating the effects of dietary behaviours on children's academic achievement has predominately focused on breakfast consumption. The aim of this study was to conduct secondary analysis to examine associations between a range of dietary behaviours and children's academic achievement. METHODOLOGY: Data on five dietary variables (fruit intake; vegetable intake; consumption of takeaway; sugar sweetened beverages; and breakfast) and scores in the five domains of a standardised academic achievement test known as NAPLAN (reading, writing, grammar/punctuation, spelling and numeracy) were obtained for Australian children aged 8-15 years in school grades three (n = 1185), five (n = 1147), seven (n = 1053) and nine (n = 860). Mixed linear models adjusted for socioeconomic status and gender were used to examine associations between dietary behaviours and academic scores. RESULTS: Greater consumption of vegetables with the evening meal (7 nights/week) was associated with higher test scores in the domains of spelling and writing (p=<0.01), with the greatest effect observed for spelling with a mean score difference of 86 ± 26.5 NAPLAN points between the highest and lowest levels of consumption (95% CI: 34.0-138.1; p=<0.01). Increased consumption of sugar sweetened beverages was associated with significantly lower test scores in reading, writing, grammar/punctuation and numeracy (<0.01). PRINCIPLE CONCLUSIONS: The findings of this study demonstrate dietary behaviours are associated with higher academic achievement. Future research should further explore relationships between a wide range of dietary behaviours and children's academic achievement.

Genetic and Environmental Influences on Literacy and Numeracy Performance in Australian School Children in Grades 3, 5, 7, and 9.

We examined the extent to which genes and the environment contributed to variation in and covariation among reading, spelling, grammar and punctuation, writing, and numeracy in Australian school children in Grades 3, 5, 7, and 9. Heritability was generally high: reading .58-.71 (excepting Grade 5 girls), spelling .68-.78; grammar and punctuation .52-.66, writing .39-.52, and numeracy .39-.79. Boys' performance varied more than girls in spelling and numeracy, and the common environment was a greater influence in girls than boys in Grade 3 numeracy and Grade 5 reading. Independent pathway models showed similar genetic and environmental structures at each grade with approximately one third to one half of the variation in each domain due to genes that influenced all domains. The covariation among the domains was largely mediated by genes. Results suggest substantial uniformity in the environmental factors influencing these academic domains.

Measures of Kindergarten Spelling and Their Relations to Later Spelling Performance.

Learning the orthographic forms of words is important for both spelling and reading. To determine whether some methods of scoring children's early spellings predict later spelling performance better than do other methods, we analyzed data from 374 U.S. and Australian children who took a 10-word spelling test at the end of kindergarten (mean age 6 years, 2 months) and a standardized spelling test approximately two years later. Surprisingly, scoring methods that took account of phonological plausibility did not outperform methods that were based only on orthographic correctness. The scoring method that is most widely used in research with young children, which allots a certain number of points to each word and which considers both orthographic and phonological plausibility, did not rise to the top as a predictor. Prediction of Grade 2 spelling performance was improved to a small extent by considering children's tendency to reverse letters in kindergarten.

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.

A retrospective longitudinal study of cognitive and language skills in poor reading comprehension.

Fifty-six specific poor reading comprehenders (SPRC) were selected in Grade 4 and retrospectively compared to good comprehenders at preschool (age 5) and at the end of kindergarten, Grade 1, and Grade 2. The results revealed deficits in vocabulary, grammar, verbal memory and early deficits in phonological awareness in most of the SPRC sample, beginning in preschool. The reading comprehension deficits in children with SPRC were not as marked in earlier assessments in Grade 1 and 2, probably because of the greater dependence on word decoding in reading comprehension in the early grades.

Validity of large-scale reading tests: A phenotypic and behaviour-genetic analysis.

Each year, all Australian students in grades 3, 5, 7, and 9 sit nationwide large-scale tests in literacy and numeracy, which have their validity frequently questioned. We compared the performance of Grade 3 twins on these large-scale reading tests with their performance on three individually administered literacy tests in comprehension, word reading and vocabulary within a genetically sensitive design. Comprehension, word reading, and vocabulary accounted for a substantial amount of the variance in school reading tests. Performance on large-scale reading tests and individually administered tests was moderately to substantially heritable and the same genes contributed to performance in both types of test. These results confirm that large-scale school reading tests measure, at least in part, the literacy skills tapped by individual tests that are frequently considered to be the "gold-standard" in testing.

Why do Children Differ in Their Development of Reading and Related Skills?

Modern behavior-genetic studies of twins in the U.S., Australia, Scandinavia, and the U.K. show that genes account for most of the variance in children's reading ability by the end of the first year of formal reading instruction. Strong genetic influence continues across the grades, though the relevant genes vary for reading words and comprehending text, and some of the genetic influence comes through a gene - environment correlation. Strong genetic influences do not diminish the importance of the environment for reading development in the population and for helping struggling readers, but they question setting the same minimal performance criterion for all children.

Longitudinal stability and predictors of poor oral comprehenders and poor decoders.

Two groups of fourth-grade children were selected from a population sample (N=926) to be either poor oral comprehenders (poor oral comprehension but normal word decoding) or poor decoders (poor decoding but normal oral comprehension). By examining both groups in the same study with varied cognitive and literacy predictors, and examining them both retrospectively and prospectively, we could assess how distinctive and stable the predictors of each deficit are. Predictors were assessed retrospectively at preschool and at the end of kindergarten, Grade 1, and Grade 2. Group effects were significant at all test occasions, including those for preschool vocabulary (worse in poor oral comprehenders) and rapid automatized naming (RAN) (worse in poor decoders). Preschool RAN and vocabulary prospectively predicted Grade 4 group membership (77-79% correct classification) within the selected samples. Reselection in preschool of "at-risk" poor decoder and poor oral comprehender subgroups based on these variables led to significant but relatively weak prediction of subtype membership at Grade 4. Implications of the predictive stability of our results for identification and intervention of these important subgroups are discussed.

The genetic and environmental etiologies of individual differences in early reading growth in Australia, the United States, and Scandinavia.

This first cross-country twin study of individual differences in reading growth from post-kindergarten to post-second grade analyzed data from 487 twin pairs from the United States, 267 twin pairs from Australia, and 280 twin pairs from Scandinavia. Data from two reading measures were fit to biometric latent growth models. Individual differences for the reading measures at post-kindergarten in the United States and Australia were due primarily to genetic influences and to both genetic and shared environmental influences in Scandinavia. In contrast, individual differences in growth generally had large genetic influences in all countries. These results suggest that genetic influences are largely responsible for individual differences in early reading development. In addition, the timing of the start of formal literacy instruction may affect the etiology of individual differences in early reading development but have only limited influence on the etiology of individual differences in growth.

Multivariate genetic analysis of learning and early reading development.

The genetic factor structure of a range of learning measures was explored in twin children, recruited in preschool and followed to Grade 2 (total N = 2084). Measures of orthographic learning and word reading were included in the analyses to determine how these patterned with the learning processes. An exploratory factor analysis of the genetic correlations among the variables indicated a three-factor model. Vocabulary tests loaded on the first factor, the Grade 2 measures of word reading and orthographic learning, plus preschool letter knowledge, loaded on the second, and the third was characterized by tests of verbal short-term memory. The three genetic factors correlated, with the second (print) factor showing the most specificity. We conclude that genetically-influenced learning processes underlying print-speech integration, foreshadowed by preschool letter knowledge, have a degree of independence from genetic factors affecting spoken language. We also argue that the psychology and genetics of associative learning be afforded a more central place in studies of reading (dis)ability, and suggest some links to molecular studies of the genetics of learning.

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.

A multivariate twin study of early literacy in Japanese Kana.

This first Japanese twin study of early literacy development investigated the extent to which genetic and environmental factors influence individual differences in prereading skills in 238 pairs of twins at 42 months of age. Twin pairs were individually tested on measures of phonological awareness, kana letter name/sound knowledge, receptive vocabulary, visual perception, nonword repetition, and digit span. Results obtained from univariate behavioral-genetic analyses yielded little evidence for genetic influences, but substantial shared-environmental influences, for all measures. Phenotypic confirmatory factor analysis suggested three correlated factors: phonological awareness, letter name/sound knowledge, and general prereading skills. Multivariate behavioral genetic analyses confirmed relatively small genetic and substantial shared environmental influences on the factors. The correlations among the three factors were mostly attributable to shared environment. Thus, shared environmental influences play an important role in the early reading development of Japanese children.