Lexical Diversity in the Spontaneous Speech of Children With Specific Language Impairment Application of D Research Article
Research Article  |   October 01, 2002
Lexical Diversity in the Spontaneous Speech of Children With Specific Language Impairment
 
Author Affiliations & Notes
  • Amanda J. Owen
    Purdue University West Lafayette, IN
  • Laurence B. Leonard
    Purdue University West Lafayette, IN
  • Contact author: Amanda J. Owen, Audiology and Speech Sciences, Heavilon Hall, Purdue University, West Lafayette, IN 47907. E-mail: ajowen@purdue.edu
Article Information
Language Disorders / Specific Language Impairment / Language / Research Articles
Research Article   |   October 01, 2002
Lexical Diversity in the Spontaneous Speech of Children With Specific Language Impairment
Journal of Speech, Language, and Hearing Research, October 2002, Vol. 45, 927-937. doi:10.1044/1092-4388(2002/075)
History: Received December 3, 2001 , Accepted April 9, 2002
 
Journal of Speech, Language, and Hearing Research, October 2002, Vol. 45, 927-937. doi:10.1044/1092-4388(2002/075)
History: Received December 3, 2001; Accepted April 9, 2002
Web of Science® Times Cited: 30

The lexical diversity of children with specific language impairment (SLI) (ages 3 years 7 months to 7 years 3 months) was compared to that of normally developing same-age peers and younger normally developing children matched according to mean length of utterance in words (MLUw). Lexical diversity was calculated from spontaneous speech samples using D, a measure that uses repeated calculations of type-token ratio (TTR) to estimate how TTR changes as the speech samples increase in size. When D computations were based on 250-word samples, developmental differences were apparent. For both children with SLI and typically developing children, older subgroups showed higher D scores than younger subgroups, and subgroups with higher MLUws showed higher D scores than subgroups with lower MLUws. Children with SLI did not differ from same-age peers. At lower MLUw levels, children with SLI showed higher D scores than younger typically developing children matched for MLUw. The developmental sensitivity of D notwithstanding, comparisons using 100-utterance samples, in which the number of lexical tokens varied as a function of the children's MLUws, and comparisons between 250- and 500-word samples revealed the possible influence of sample size on this measure. However, analysis of the effect sizes using smaller and larger samples revealed that D is not affected by sample size to the degree seen for more traditional measures of lexical diversity.

Acknowledgments
The research reported here was supported in part by research grant 5 R01 DC00458 from the National Institute of Deafness and Other Communication Disorders, National Institutes of Health, and by training grant 5 T32 DC00030 from the National Institutes of Health. The authors thank Brian Richards, University of Reading, for offering comments on particular details of this study.
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