Longitudinal Twin Study of Early Literacy Development: Preschool and Kindergarten Phases

Abstract

Abstract. Grade 1 literacy skills of twin children in Australia (New South Wales) and the United States (Colorado) were explored in a genetically sensitive design (N = 319 pairs). Analyses indicated strong genetic influence on word and nonword identification, reading comprehension, and spelling. Rapid naming showed more modest, though reliable, genetic influence. Phonological awareness was subject to high nonshared environment and no reliable genetic effects, and individual measures of memory and learning were also less affected by genes than nonshared environment. Multivariate analyses showed that the same genes affected word identification, reading comprehension, and spelling. Country comparisons indicated that the patterns of genetic influence on reading and spelling in Grade 1 were similar, though for the U.S. but not the Australian children new genes came on stream in the move from kindergarten to Grade 1. We suggest that this is because the more intensive kindergarten literacy curriculum in New South Wales compared with Colorado, consistent with the mean differences between the two countries, means that more of the genes are ''online'' sooner in Australia because of accelerated overall reading development.

Genetic and environmental effects of serial naming and phonological awareness on early reading outcomes.

“…However, the importance of shared environment in the overlap among early reading skills is consistent with our own univariate examination of WRRP (Petrill et al, 2006) as well with univariate results reported by Byrne et al (2002Byrne et al ( , 2005. Moreover, these results are somewhat consistent with the typically developing sample described by Compton et al (2001).…”

“…We conducted a series of Cholesky decomposition analyses (see Neale & Cardon, 1992) similar to those used in Compton et al (2001) and Byrne et al (2005). As shown in Figure 1, the covariance among phonological awareness, RAN, and outcomes (Word ID and PD, in separate analyses) was parameterized using nine latent factors.…”

“…This inconsistency could be due to sampling and measurement differences between the two studies. In terms of sampling, Byrne et al (2005) involved U.S., Australian, and Scandinavian samples, whereas our study examined a U.S. sample only. In addition, Byrne et al (2005) used a composite of the Comprehensive Test of Phonological Processing's (Wagner et al, 1999) colors and shapes, whereas the current study involved a composite of letters and numbers, corrected for age, sex, and letter identification.…”

“…In terms of sampling, Byrne et al (2005) involved U.S., Australian, and Scandinavian samples, whereas our study examined a U.S. sample only. In addition, Byrne et al (2005) used a composite of the Comprehensive Test of Phonological Processing's (Wagner et al, 1999) colors and shapes, whereas the current study involved a composite of letters and numbers, corrected for age, sex, and letter identification. Despite these differences, both studies converge on the general idea that shared environment may be more important in early literacy and that genetics are important for the overlap among phonological awareness, RAN, and reading outcomes.…”

Genetic and environmental influences on early speech, language and literacy development

“…In addition, reading difficulties have been found to be more heritable in groups of children who also have deficits in phonological short-term memory (Bishop, 2001;Bishop, Adams & Norbury, 2004), suggesting that the close genetic relationship between phonology and reading extends beyond phonological awareness to the phonological system more generally. This pattern also holds longitudinally, in that the genetic factors influencing phonological awareness in preschool go on to affect children's reading a year later (Byrne et al, 2005). Less well established is the nature of the relationship between non-phonological language skills and reading.…”