Grammar Clinical Marker Yields Substantial Heritability for Language Impairments in 16-Year-Old Twins Purpose There is a need for well-defined language phenotypes suitable for adolescents in twin studies and other large-scale research projects. Rice, Hoffman, and Wexler (2009)  have developed a grammatical judgment measure as a clinical marker of language impairment, which has an extended developmental range to adolescence. Method We ... Research Article
Research Article  |   January 22, 2018
Grammar Clinical Marker Yields Substantial Heritability for Language Impairments in 16-Year-Old Twins
 
Author Affiliations & Notes
  • Philip S. Dale
    Department of Speech & Hearing Sciences, University of New Mexico, Albuquerque
  • Mabel L. Rice
    Department of Speech-Language-Hearing: Sciences & Disorders, The University of Kansas, Lawrence
  • Kaili Rimfeld
    Social, Genetic & Developmental Psychiatry Research Centre, Institute of Psychiatry, Psychology & Neuroscience, King's College London, United Kingdom
  • Marianna E. Hayiou-Thomas
    Department of Psychology, University of York, United Kingdom
  • 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 Philip S. Dale: dalep@unm.edu
  • Editor: Krista Wilkinson
    Editor: Krista Wilkinson×
  • Associate Editor: Carol Miller
    Associate Editor: Carol Miller×
Article Information
Special Populations / Genetic & Congenital Disorders / Language Disorders / Language / Research Articles
Research Article   |   January 22, 2018
Grammar Clinical Marker Yields Substantial Heritability for Language Impairments in 16-Year-Old Twins
Journal of Speech, Language, and Hearing Research, January 2018, Vol. 61, 66-78. doi:10.1044/2017_JSLHR-L-16-0364
History: Received September 14, 2016 , Revised March 16, 2017 , Accepted August 15, 2017
 
Journal of Speech, Language, and Hearing Research, January 2018, Vol. 61, 66-78. doi:10.1044/2017_JSLHR-L-16-0364
History: Received September 14, 2016; Revised March 16, 2017; Accepted August 15, 2017

Purpose There is a need for well-defined language phenotypes suitable for adolescents in twin studies and other large-scale research projects. Rice, Hoffman, and Wexler (2009)  have developed a grammatical judgment measure as a clinical marker of language impairment, which has an extended developmental range to adolescence.

Method We conducted the first twin analysis, along with associated phenotypic analyses of validity, of an abridged, 20-item version of this grammatical judgment measure (GJ-20), based on telephone administration using prerecorded stimuli to 405 pairs of 16-year-olds (148 monozygotic and 257 dizygotic) drawn from the Twins Early Development Study (Haworth, Davis, & Plomin, 2012).

Results The distribution of scores is markedly skewed negatively, as expected for a potential clinical marker. Low performance on GJ-20 is associated with lower maternal education, reported learning disability (age 7 years), and low scores on language tests administered via the Twins Early Development Study (age 16 years) as well as General Certificate of Secondary Education English and Math examination performance (age 16 years). Liability threshold estimates for the genetic influence on low performance on GJ-20 are substantial, ranging from 36% with a lowest 10% criterion to 74% for a lowest 5% criterion.

Conclusions The heritability of GJ-20 scores, especially at more extreme cutoffs, along with the score distribution and association with other indicators of language impairments, provides additional evidence for the potential value of this measure as a clinical marker of specific language impairment.

Acknowledgment
The Twins Early Development Study is supported by a program grant (MR/M021475/1 and previously G0901245) from the UK Medical Research Council, awarded to Robert Plomin. We gratefully acknowledge the ongoing contribution of the participants in the Twins Early Development Study and their families. We also appreciate advice on statistical procedures from Fruhling Rijsdijk of the Social, Genetic & Developmental Psychiatry Research Centre.
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