Rs. Chapman et al., LANGUAGE-SKILLS OF CHILDREN AND ADOLESCENTS WITH DOWN-SYNDROME - II -PRODUCTION DEFICITS, Journal of speech language and hearing research, 41(4), 1998, pp. 861-873
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.