Heritability of Poor Language Achievement Among Twins In order to examine the basis of familial associations with poor language achievement, 62 twinship pairs and 3 sets of triplets were studied in which at least one member presented poor oral language status in the absence of other developmental or sensory impairments. Rates of concordance for poor language were ... Research Article
Research Article  |   February 01, 1998
Heritability of Poor Language Achievement Among Twins
 
Author Affiliations & Notes
  • J. Bruce Tomblin
    The University of Iowa Iowa City
  • Paula R. Buckwalter
    The University of Iowa Iowa City
  • Contact author: J. Bruce Tomblin, PhD, Department of Speech Pathology and Audiology, University of Iowa, Iowa City, IA 52242. Email: J-Tomblin@UIOWA.EDU
Article Information
Special Populations / Genetic & Congenital Disorders / Language Disorders / Language / Research Articles
Research Article   |   February 01, 1998
Heritability of Poor Language Achievement Among Twins
Journal of Speech, Language, and Hearing Research, February 1998, Vol. 41, 188-199. doi:10.1044/jslhr.4101.188
History: Received August 12, 1996 , Accepted June 9, 1997
 
Journal of Speech, Language, and Hearing Research, February 1998, Vol. 41, 188-199. doi:10.1044/jslhr.4101.188
History: Received August 12, 1996; Accepted June 9, 1997

In order to examine the basis of familial associations with poor language achievement, 62 twinship pairs and 3 sets of triplets were studied in which at least one member presented poor oral language status in the absence of other developmental or sensory impairments. Rates of concordance for poor language were compared between the monozygotic (MZ) and dizygotic (DZ) pairs. Concordance for the MZ pairs was .96, whereas it was .69 for the DZ pairs. The DeFries-Fulker method for computing heritability of extreme scores was employed yielding a h2g of .45. Similar results were obtained for those pairs containing only children with performance IQs above 85, but with at least one member having language below –1 SD. A comparison of DZ twins with singleton sibling pairs with at least one affected member and of similar age showed that DZ twins were more similar with respect to language achievement than singleton pairs. Thus, twinning appeared to have influenced twin resemblance among those where at least one member presented poor language achievement. These results support the hypothesis that genetic factors contribute to the liability of poor language achievement in children who do not present other developmental or sensory disorders.

Acknowledgments
This study was supported by grant NIH-DC-19-90 from the National Institute on Deafness and Other Communication Disorders. The authors wish to thank Jeff Gilger for his helpful comments on a previous version of this manuscript. They also wish to thank the National Organization of Mothers of Twins Clubs, local twin clubs, the Iowa High Risk Birth Registry, and the Minneapolis School System and all of the speech-language clinicians who helped recruit our twins. A special thanks to all of the twins and their families for participating.
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