Article/Report  |   June 2008
Why Do Preschool Language Abilities Correlate With Later Reading? A Twin Study
Author Affiliations & Notes
  • Nicole Harlaar
    King’s College London, England
  • Marianna E. Hayiou-Thomas
    University of York, United Kingdom
  • Philip S. Dale
    University of New Mexico, Albuquerque
  • Robert Plomin
    King’s College London, England
  • Contact author: Nicole Harlaar, who is now at the Department of Human Development and Family Science, The Ohio State University, 135 Campbell Hall, 1787 Neil Avenue, Columbus, OH 43210. E-mail: nharlaar@ehe.osu.edu.
Development / Special Populations / Genetic & Congenital Disorders / School-Based Settings / Attention, Memory & Executive Functions / Language
Article/Report   |   June 2008
Why Do Preschool Language Abilities Correlate With Later Reading? A Twin Study
Journal of Speech, Language, and Hearing Research June 2008, Vol.51, 688-705. doi:10.1044/1092-4388(2008/049)
History: Accepted 04 Sep 2007 , Received 23 Jun 2006 , Revised 30 Nov 2006
Journal of Speech, Language, and Hearing Research June 2008, Vol.51, 688-705. doi:10.1044/1092-4388(2008/049)
History: Accepted 04 Sep 2007 , Received 23 Jun 2006 , Revised 30 Nov 2006

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.

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