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Children with developmental language impairment have vocabulary deficits characterized by limited breadth and depth
Author(s) -
McGregor Karla K.,
Oleson Jacob,
Bahnsen Alison,
Duff Dawna
Publication year - 2013
Publication title -
international journal of language and communication disorders
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.101
H-Index - 67
eISSN - 1460-6984
pISSN - 1368-2822
DOI - 10.1111/1460-6984.12008
Subject(s) - psychology , vocabulary , developmental psychology , specific language impairment , vocabulary development , typically developing , longitudinal study , language impairment , language disorder , language development , cognition , linguistics , teaching method , mathematics education , statistics , psychiatry , philosophy , mathematics , autism
Background Deficient vocabulary is a frequently reported symptom of developmental language impairment, but the nature of the deficit and its developmental course are not well documented. Aims To describe the nature of the deficit in terms of breadth and depth of vocabulary knowledge and to determine whether the nature and the extent of the deficit change over the school years. Methods & Procedures A total of 25 681 oral definitions produced by 177 children with developmental language impairment (LI) and 325 grade‐mates with normally developing language (ND) in grades 2, 4, 8 and 10 were taken from an existing longitudinal database. We analysed these for breadth by counting the number of words defined correctly and for depth by determining the amount of information in each correct definition. Via a linear mixed model, we determined whether breadth and depth varied with language diagnosis independent of non‐verbal IQ, mothers’ education level, race, gender, income and (for depth only) word. Outcomes & Results Children with LI scored significantly lower than children with ND on breadth and depth of vocabulary knowledge in all grades. The extent of the deficit did not vary significantly across grades. Language diagnosis was an independent predictor of breadth and depth and as strong a predictor as maternal education. For the LI group, growth in depth relative to breadth was slower than for the ND group. Conclusions & Implications Compared with their grade‐mates, children with LI have fewer words in their vocabularies and they have shallower knowledge of the words that are in their vocabularies. This deficit persists over developmental time.