6.

Chapman et al. (2002)

31 American DS (CA: 5 - 20 years)

3-hour protocol: hearing screening, TACL-R, PPVT-R, MLU-S from 12-min narrative language samples, Stanford Binet (4th ed.) Bead Memory and Pattern Analysis subtests, digit span subtest of the Illinois Test of Psycholinguistic Ability (ITPA), and the Nonword Repetition Test

Individual differences in expressive language syntax at study start are best predicted by syntax comprehension. Syntax comprehension across the 6 years of study participation is best predicted by age at study start and measures of short-term memory (auditory + visual), while change in syntax comprehension across this time is predicted by age at study start.

The expressive language acquisition continues in adolescence for most individuals with DS, and is predicted by syntax comprehension and its growth trajectory. The rate of MLU increase is greatest for those for whom comprehension declined less.

However, no evidence of a critical period.

DS speakers: more advanced content than is typical for their average utterance length, thus need for more complex expressive syntax.

Measures of syntax development which focused on comprehension rather than on production might depict different longitudinal outcomes of loss, plateauing, or gain depending on age.

7.

Chapman et al. (1998)

47 American DS (CA: 5.6 - 20.6 years)/47 TDC (CA: 2.2 - 6.1 years)

3-hour protocol: hearing screening; picture descriptions; story retelling; Form L of the PPVT-R; 6 min. conversation and 12 min. narration with the examiner; an object hiding task

evaluating fast mapping for a

novel noun (Chapman et al., 1990) ; the Expressive Vocabulary, Bead Memory, and Pattern Analysis subtests of the Stanford-Binet, 4th edition; conversation and snack with a parent; a speech motor evaluation; delayed

story recall; event narration; the TACL-R; the delay condition of the object-hiding task administered earlier.

No evidence for a slowing of lexical or syntactic development from age group 2 (8 - 12 years) on or from age group 3 (12 - 16 years) on, no evidence of a critical period for language development ending at adolescence, nor of a “syntactic ceiling” at MLU corresponding to simple sentences for the DS group.

DS: specific language impairment compared to control children, in number of different words and total words (in the first 50 utterances) and in MLU.

Clear evidence of a deficit in the DS group’s expressive language performance across measures of syntactic complexity, word frequency, diversity in a fixed number of utterances, and rate of word production, despite more frequent utterances per minute, in both conversational and narrative samples.

8.

Chapman et al. (1991)

48 American DS (CA: 5.6 - 20.6 years)/48 TDC (CA: 2 - 6 years)

3-hr protocol: hearing screening, picture descriptions, story retelling, Form L of the PPVT-Revised, conversation and narration with the examiner, an object hiding task (Chapman et al., 1990) , the Expressive Vocabulary, Bead Memory, and Pattern Analysis subtests of the Stanford-Binet, 4th ed., conversation and snack with a parent, a speech motor evaluation, delayed story recall, event narration, the Test for Auditory Comprehension of Language Revised, and the delay condition of the object hiding task

Differences within the group of DS between lexical and syntactic comprehension skill increasing with age, as well as between nonverbal cognitive subtests of pattern analysis and short-term memory for bead arrangements.

CA and mean MA, collectively, accounted for 80% of the variability in syntax comprehension and hearing status predicted an additional 4%.

Overall, adolescents with DS can be described as having advanced vocabulary comprehension, and also have appeared to have mild deficits in syntax comprehension.

Their results are consistent with findings of sequential processing deficits or visual storage deficits.