A broadened estimate of syntactic and lexical ability from the MB-CDI.
Trevor K M Day, Jed T Elison
PMID 33973510WHAT IT FOUND
On the MB-CDI Words & Sentences form, everyday word knowledge and grammar/function word knowledge separate.
Grammar lags words, beginning around 20 to 24 months, and the 8 to 18 month form does not give a usable grammar score.
Key findings
01The Words & Sentences form separates into a lexical estimate of content words and a structural estimate that includes function words, word forms, word endings, and sentence complexity.
02Syntactic ability only begins to grow roughly in the 20 to 24 month age range, remains lower than lexical ability, and does not consolidate by 30 months.
03The 8 to 18 month Words & Gestures form did not produce a clear lexical/structural separation, and its confirmatory analyses did not converge.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The sample was not meant to include children with developmental disorders, so it does not show how these scores behave in children with language difficulties. The model fit was marginal, and the authors say an instrument geared toward distinguishing function and content words could perform better. The Words & Gestures analysis was unclear, partly because only 8% of subcategory scores exceeded 30% endorsed. Sex and mother's education analyses included 3,841 children because of missing data. The study did not follow individual children over time; the authors suggest a longitudinal analysis might clarify Words & Gestures scores. The lexical and structural measures remained highly correlated (.79 in factor scores and .87 in the one-weighted analysis), so their separate effects are difficult to distinguish.
The easy way to misread this
Do not read these factor scores as a diagnostic cut-off or as proof that a child has a language disorder. The sample was not meant to include children with developmental disorders, and the Words & Gestures form did not give a usable structural score.