Taxometric Analyses of Specific Language Impairment in 6-Year-Old Children PurposeTo determine whether language scores at age 6 years suggest that specific language impairments (SLIs) distribute in a categorical or in a dimensional fashion.MethodA taxometric analysis of language scores from 601 six-year-old children who were free of neonatal risk factors was performed. From among 4 candidate indicators of SLI, 2 ... Article
Article  |   October 01, 2011
Taxometric Analyses of Specific Language Impairment in 6-Year-Old Children
 
Author Notes
  • Correspondence to Christine A. Dollaghan: dollaghan@utdallas.edu
  • Editor: Janna Oetting
    Editor: Janna Oetting×
  • Associate Editor: Ron Gillam
    Associate Editor: Ron Gillam×
Article Information
Language Disorders / Specific Language Impairment / Language
Article   |   October 01, 2011
Taxometric Analyses of Specific Language Impairment in 6-Year-Old Children
Journal of Speech, Language, and Hearing Research, October 2011, Vol. 54, 1361-1371. doi:10.1044/1092-4388(2011/10-0187)
History: Received June 30, 2010 , Revised January 12, 2011 , Accepted February 11, 2011
 
Journal of Speech, Language, and Hearing Research, October 2011, Vol. 54, 1361-1371. doi:10.1044/1092-4388(2011/10-0187)
History: Received June 30, 2010; Revised January 12, 2011; Accepted February 11, 2011
Web of Science® Times Cited: 11

PurposeTo determine whether language scores at age 6 years suggest that specific language impairments (SLIs) distribute in a categorical or in a dimensional fashion.

MethodA taxometric analysis of language scores from 601 six-year-old children who were free of neonatal risk factors was performed. From among 4 candidate indicators of SLI, 2 were eligible for the mean above minus below a cut (MAMBAC) procedure (Meehl & Yonce, 1994): number of different words (NDW) produced in a language sample and average percentage phonemes repeated correctly in 3- and 4-syllable nonwords (3–4 PPC). Graphs of these MAMBAC variables were inspected to determine whether they patterned in a manner suggesting the presence of a discrete category, having either a central peak or a steep curve peaking near the final interval.

ResultsMAMBAC curves for NDW and 3–4 PPC did not suggest the presence of a taxon, and results did not vary during consistency checks in which MAMBAC parameters and cutoff values for language deficits were manipulated.

ConclusionsResults suggest that for these measures, children with specific language deficits are those falling at the lower end of a continuous distribution of language skills rather than a qualitatively distinct group.

Acknowledgments
Data for these analyses were obtained originally in the course of a research project led by Jack L. Paradise, MD, and were supported by the National Institute of Child Health and Human Development, the Agency for Healthcare Research and Quality, and the National Institutes of Health General Clinical Research Center, as well as by gifts from SmithKline Beecham Laboratories and Pfizer. I am indebted to the children and families who participated and to the research team involved in the original project, including Jack L. Paradise, Thomas F. Campbell, Heidi M. Feldman, Dayna L. Pitcairn, D. Kathleen Colborn, Beverly S. Bernard, Clyde G. Smith, Howard E. Rockette, Janine E. Janosky, Marcia Kurs-Lasky, and many student research assistants from the University of Pittsburgh Department of Communication Science and Disorders.
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