LANGUAGE-SKILLS OF CHILDREN AND ADOLESCENTS WITH DOWN-SYNDROME - II -PRODUCTION DEFICITS

Hypotheses that children and adolescents with Down syndrome show (a) a specific expressive language impairment, (b) a critical period'' for language acquisition, (c) a ''simple sentence syntactic ceiling'' in p roduction, and (d) deficit in grammatical morphology were investigated cross-sectionally Conversational and narrative language samples from 47 children and adolescents with Down syndrome (Trisomy 21), aged 5 to 20 years, were compared to those from 47 control children aged 2 to 6 years matched statistically for nonverbal mental age. Children with D own syndrome appear to have a specific language impairment, compared t o control children, in number of different words and total words (in t he first 50 utterances) and in mean length of utterance (MLU). Total u tterance attempts per minute were more frequent in the Down syndrome g roup. Narrative samples contained more word tokens, more word types, a nd longer MLU than conversation samples, for both groups. Intelligibil ity of narratives was significantly poorer for the Down syndrome group than controls. Analyses of narrative language sample by age sub-group showed no evidence of a critical period for language development endi ng at adolescence, nor of a ''syntactic ceiling'' at MLUs correspondin g to simple sentences for the Down syndrome group. Omissions of word t okens and types were more frequent in the older Down syndrome than the younger control sample, matched on MLU.