This study examined whether autism spectrum toddlers and late talkers, matched on overall productive vocabulary, display similar use of 1) semantic categories; 2) psychological terms; and 3) word combinations and grammatical complexity.
Two groups of toddlers (22-35 months) participated: 21 AUT and 21 LT. AUT diagnoses were determined using comprehensive diagnostic evaluations including the ADI-R and ADOS. Groups were matched on parent report of words produced (± 6 words) on the Communicative Development Index: Words and Sentences (CDI-WS).
Vocabulary matching resulted in significant mean age differences between the groups (AUT=30 mo, LT=25 mo). Comparison of the proportions of words within 22 semantic categories on the CDI-WS revealed equivalent usage for all categories except action words (higher for AUT). An analysis of psychological terms (e.g., “happy”) revealed no significant differences for any of five categories evaluated or overall proportion of terms used. With respect to grammatical abilities, there were no significant differences in CDI complexity scores or the proportion of AUT vs. LT toddlers who were combining words.
When matched on overall vocabulary level, 30-month AUT toddlers exhibited word use patterns and early grammatical abilities that were qualitatively very similar to 25-month late talkers without autism. These initial findings support the dimensional account of language delay relative to vocabulary/grammar in autism.