Predicting Literacy at Age 7 From Preliteracy at Age 4: A Longitudinal Genetic Analysis

Arithmetic, reading and writing performance has a strong genetic component: A study in primary school children

Even children attending the same primary school and taught by the same teacher differ greatly in their performance. In the Netherlands, performance at the end of primary school determines the enrollment in a particular level of secondary education. Identifying the impact of genes and the environment on individual differences in educational achievement between children is important. The Netherlands Twin Register has collected data on scores of tests used in primary school (ages 6 to 12) to monitor a child's educational progress in four domains, i.e. arithmetic, word reading, reading comprehension and spelling (1058 MZ and 1734 DZ twin pairs), and of a final test (2451 MZ and 4569 DZ twin pairs) in a large Dutch cohort. In general, individual differences in educational achievement were to a large extent due to genes and the influence of the family environment was negligible. Moreover, there is no evidence for gender differences in the underlying etiology.

Why does parental language input style predict child language development? A twin study of gene-environment correlation

There are well-established correlations between parental input style and child language development, which have typically been interpreted as evidence that the input style causes, or influences the rate of, changes in child language. We present evidence from a large twin study (TEDS; 8395 pairs for this report) that there are also likely to be both child-to-parent effects and shared genetic effects on parent and child. Self-reported parental language style at child age 3 and age 4 was aggregated into an 'informal language stimulation' factor and a 'corrective feedback' factor at each age; the former was positively correlated with child language concurrently and longitudinally at 3, 4, and 4.5 years, whereas the latter was weakly and negatively correlated. Both parental input factors were moderately heritable, as was child language. Longitudinal bivariate analysis showed that the correlation between the language stimulation factor and child language was significantly and moderately due to shared genes. There is some suggestive evidence from longitudinal phenotypic analysis that the prediction from parental language stimulation to child language includes both evocative and passive gene-environment correlation, with the latter playing a larger role.

LEARNING OUTCOMES

The reader will understand why correlations between parental language and rate of child language are by themselves ambiguous, and how twin studies can clarify the relationship. The reader will also understand that, based on the present study, at least two aspects of parental language style - informal language stimulation and corrective feedback - have substantial genetic influence, and that for informal language stimulation, a substantial portion of the prediction to child language represents the effect of shared genes on both parent and child. It will also be appreciated that these basic research findings do not imply that parental language input style is unimportant or that interventions cannot be effective.

Do preschool children learn to read words from environmental prints?

Parents and teachers worldwide believe that a visual environment rich with print can contribute to young children's literacy. Children seem to recognize words in familiar logos at an early age. However, most of previous studies were carried out with alphabetic scripts. Alphabetic letters regularly correspond to phonological segments in a word and provide strong cues about the identity of the whole word. Thus it was not clear whether children can learn to read words by extracting visual word form information from environmental prints. To exclude the phonological-cue confound, this study tested children's knowledge of Chinese words embedded in familiar logos. The four environmental logos were employed and transformed into four versions with the contextual cues (i.e., something apart from the presentation of the words themselves in logo format like the color, logo and font type cues) gradually minimized. Children aged from 3 to 5 were tested. We observed that children of different ages all performed better when words were presented in highly familiar logos compared to when they were presented in a plain fashion, devoid of context. This advantage for familiar logos was also present when the contextual information was only partial. However, the role of various cues in learning words changed with age. The color and logo cues had a larger effect in 3- and 4- year-olds than in 5-year-olds, while the font type cue played a greater role in 5-year-olds than in the other two groups. Our findings demonstrated that young children did not easily learn words by extracting their visual form information even from familiar environmental prints. However, children aged 5 begin to pay more attention to the visual form information of words in highly familiar logos than those aged 3 and 4.

Literacy and numeracy are more heritable than intelligence in primary school

Because literacy and numeracy are the focus of teaching in schools, whereas general cognitive ability (g, intelligence) is not, it would be reasonable to expect that literacy and numeracy are less heritable than g. Here, we directly compare heritabilities of multiple measures of literacy, numeracy, and g in a United Kingdom sample of 7,500 pairs of twins assessed longitudinally at ages 7, 9, and 12. We show that differences between children are significantly and substantially more heritable for literacy and numeracy than for g at ages 7 and 9, but not 12. We suggest that the reason for this counterintuitive result is that universal education in the early school years reduces environmental disparities so that individual differences that remain are to a greater extent due to genetic differences. In contrast, the heritability of g increases during development as individuals select and create their own environments correlated with their genetic propensities.

The etiology of diverse receptive language skills at 12 years

PURPOSE

In the 2nd decade of life, language skills expand in both quantitative and qualitative ways. The etiology of these new skills and the relationships among them have been little explored.

METHOD

Taking advantage of widespread access to inexpensive and fast Internet connections in the United Kingdom, we administered four Web-based measures of receptive language development--Vocabulary, Listening Grammar, Figurative Language, and Making Inferences--to a sample of 12-year-old twin pairs (N=4,892) participating in the Twins Early Development Study (TEDS; Oliver & Plomin, 2007).

RESULTS

The 4 measures showed moderate phenotypic intercorrelation. All 4 showed moderate genetic influence (a2 between .25 and .36) and low shared environmental influence (c2 between .13 and .19). The median genetic correlation among the 4 measures was .87, indicating strong genetic overlap among them. A latent factor score for Language, based on the common variance among the measures, showed substantial genetic influence (a2=.59) and moderate shared environmental influence (c2=.28). A small but significant sex difference favored females on the Listening Grammar and Making Inferences tests, but there was no evidence for sex differences in the etiology of any of the measures.

CONCLUSION

Despite the emergence of new skills at this developmental period, from the etiological perspective, language skills remain relatively undifferentiated at an etiological level.

Environmental influences on the longitudinal covariance of expressive vocabulary: measuring the home literacy environment in a genetically sensitive design

BACKGROUND

Despite the well-replicated relationship between the home literacy environment and expressive vocabulary, few studies have examined the extent to which the home literacy environment is associated with the development of early vocabulary ability in the context of genetic influences. This study examined the influence of the home literacy environment on the longitudinal covariance of expressive vocabulary within a genetically sensitive design.

METHODS

Participants were drawn from the Western Reserve Reading Project, a longitudinal twin project of 314 twin pairs based in Ohio. Twins were assessed via three annual home visits during early elementary school; expressive vocabulary was measured via the Boston Naming Test (BNT), and the Home Literacy Environment (HLE) was assessed using mothers' report.

RESULTS

The heritability of the BNT was moderate and significant at each measurement occasion, h(2) = .29-.49, as were the estimates of the shared environment, c(2) = .27-.39. HLE accounted for between 6-10% of the total variance in each year of vocabulary assessment. Furthermore, 7-9% of the total variance of the stability over time in BNT was accounted for by covariance in the home literacy environment.

CONCLUSIONS

These results indicate that aspects of the home literacy environment, as reported by mothers, account for some of the shared environmental variance associated with expressive vocabulary in school aged children.

Early parental depression and child language development

OBJECTIVE

To examine the effects of early maternal and paternal depression on child expressive language at age 24 months and the role that parent-to-child reading may play in this pathway.

PARTICIPANTS AND METHODS

The 9-month and 24-month waves from a national prospective study of children and their families, the Early Childhood Longitudinal Study - Birth Cohort (ECLS-B), provided data on 4,109 two-parent families. Depressive symptoms were measured with a short form of the Center for Epidemiologic Studies Depression Scale (CES-D). Parents reported on positive parent-infant interactions, child expressive vocabulary, and demographic and health information at child age 9 and 24 months. Linear regression was used to estimate associations between depression, parenting, and child vocabulary. Structural equation modeling was used to test the hypothesis that parent reading behavior mediates the parent depression to child vocabulary pathway. These models were adjusted for demographic indicators.

RESULTS

As previously reported from this national sample, 14% of mothers and 10% of fathers exhibited elevated levels of depressive symptoms at 9 months. For both mothers and fathers, depression at 9 months was negatively associated with contemporaneous parent-to-child reading. Only for fathers, however, was earlier depression associated with later reading to child and related child expressive vocabulary development. A model describing this pathway demonstrated a significant indirect pathway from depression to vocabulary via parent reading to child.

CONCLUSIONS

Depression is a significant problem among both mothers and fathers of young children, but has a more marked impact on the father's reading to his child and, subsequently, the child's language development.

Why do preschool language abilities correlate with later reading? A twin study

PURPOSE

Language acquisition is predictive of successful reading development, but the nature of this link is poorly understood.

METHOD

A sample of 7,179 twin pairs was assessed on parent-report measures of syntax and vocabulary at ages 2, 3, and 4 years and on teacher assessments of reading achievement (RA) at ages 7, 9, and 10 years. These measures were used to construct latent factors of early language ability (LA) and RA in structural equation model-fitting analyses.

RESULTS

The phenotypic correlation between LA and RA (r = .40) was primarily due to shared environmental influences that contribute to familial resemblance. These environmental influences on LA and RA overlapped substantially (rC = .62). Genetic influences made a significant but smaller contribution to the phenotypic correlation between LA and RA, and showed moderate overlap (rA = .36). There was also evidence for a direct causal influence of LA on RA.

CONCLUSIONS

The association between early language and later reading is underpinned by common environmental and genetic influences. The effects of some risk factors on RA may be mediated by language. The results provide a foundation for more fine-grained studies that examine links between specific measures of language, reading, genes, and environments.

From Learning to Read to Reading to Learn: Substantial and Stable Genetic Influence

Little is known about the underlying causes and developmental patterns of stability and change in early reading abilities. In a longitudinal study of twins (n=4,291 pairs), individual differences in reading achievement assessed by teachers using U.K. National Curriculum (NC) criteria showed substantial heritabilities at ages 7, 9, and 10 years (.57-.67) and modest shared environmental influences (.10-.17). Stability in NC scores was primarily mediated genetically. There was also evidence for age-specific genetic influences at each age. Genetic influences on reading are substantial and stable during the elementary school years despite the shift from "learning to read" to "reading to learn."

Literacy and mental disorders

PURPOSE OF REVIEW

This review examines recent evidence on the comorbidity between literacy problems and psychiatric disorder in childhood and discusses possible contributory factors.

RECENT FINDINGS

Recent studies confirm the substantial overlap of literacy problems with a range of emotional/behavioural difficulties in childhood. Literacy problems and inattention may share genetic influences, contributing to associations with attention deficit hyperactivity disorder. To an extent, links with conduct problems may be also mediated by attentional difficulties. In addition, findings suggest bidirectional influences whereby disruptive behaviours impede reading progress and reading failure exacerbates risk for behaviour problems. Associations between literacy problems and anxiety disorders are not entirely mediated by inattentiveness. Rather, comorbid anxiety disorders seem likely to arise from the stressors associated with reading failure. Findings in relation to depression are less consistent, but suggest that poor readers may be vulnerable to low mood. Children with autism seem more likely to face problems in reading comprehension than the decoding difficulties more prominent in other disorders.

SUMMARY

Literacy problems are associated with increased risks of both externalizing and internalizing disorders in childhood, with different mechanisms likely to be implicated in each case. When comorbid problems occur, each is likely to require separate treatment.