Longitudinal Effects on Early Adolescent Language: A Twin Study Purpose We evaluated genetic and environmental contributions to individual differences in language skills during early adolescence, measured by both language sampling and standardized tests, and examined the extent to which these genetic and environmental effects are stable across time. Method We used structural equation modeling on latent factors ... Research Article
Research Article  |   October 01, 2016
Longitudinal Effects on Early Adolescent Language: A Twin Study
 
Author Affiliations & Notes
  • Nicole Harlaar
    School of Medicine, University of Colorado, Aurora
  • Laura Segebart DeThorne
    University of Illinois at Urbana–Champaign
  • Jamie Mahurin Smith
    Illinois State University, Normal
  • Mariana Aparicio Betancourt
    University of Illinois at Urbana–Champaign
  • Stephen A. Petrill
    The Ohio State University, Columbus
  • Nicole Harlaar and Laura Segebart DeThorne contributed equally to this article.
    Nicole Harlaar and Laura Segebart DeThorne contributed equally to this article.×
  • Disclosure: The authors have declared that no competing interests existed at the time of publication.
    Disclosure: The authors have declared that no competing interests existed at the time of publication. ×
  • Correspondence to Nicole Harlaar: nicole.harlaar@ucdenver.edu
  • Editor: Rhea Paul
    Editor: Rhea Paul×
  • Associate Editor: Andrew Whitehouse
    Associate Editor: Andrew Whitehouse×
Article Information
Special Populations / Genetic & Congenital Disorders / Research Issues, Methods & Evidence-Based Practice / Language Disorders / Language / Research Articles
Research Article   |   October 01, 2016
Longitudinal Effects on Early Adolescent Language: A Twin Study
Journal of Speech, Language, and Hearing Research, October 2016, Vol. 59, 1059-1073. doi:10.1044/2016_JSLHR-L-15-0257
History: Received July 22, 2015 , Revised December 1, 2015 , Accepted February 2, 2016
 
Journal of Speech, Language, and Hearing Research, October 2016, Vol. 59, 1059-1073. doi:10.1044/2016_JSLHR-L-15-0257
History: Received July 22, 2015; Revised December 1, 2015; Accepted February 2, 2016

Purpose We evaluated genetic and environmental contributions to individual differences in language skills during early adolescence, measured by both language sampling and standardized tests, and examined the extent to which these genetic and environmental effects are stable across time.

Method We used structural equation modeling on latent factors to estimate additive genetic, shared environmental, and nonshared environmental effects on variance in standardized language skills (i.e., Formal Language) and productive language-sample measures (i.e., Productive Language) in a sample of 527 twins across 3 time points (mean ages 10–12 years).

Results Individual differences in the Formal Language factor were influenced primarily by genetic factors at each age, whereas individual differences in the Productive Language factor were primarily due to nonshared environmental influences. For the Formal Language factor, the stability of genetic effects was high across all 3 time points. For the Productive Language factor, nonshared environmental effects showed low but statistically significant stability across adjacent time points.

Conclusions The etiology of language outcomes may differ substantially depending on assessment context. In addition, the potential mechanisms for nonshared environmental influences on language development warrant further investigation.

Acknowledgments
This project was supported by National Institute of Child Health and Human Development Grants HD38075, HD46167, and HD050307 (awarded to Stephen Petrill). In addition to our appreciation of all participating families, we want to extend thanks to other WRRMP coinvestigators: Kirby Deater-Deckard, Lee Anne Thompson, and Christopher Schatschneider. Last, thanks to all participating members of the Child Language and Literacy Laboratory, particularly Karissa Nulty and Clare Rogers for assistance with data management and analyses.
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