Sentence comprehension in adolescents with Down syndrome and typically developing children: role of sentence voice, visual context, and auditory-verbal short-term memory.

The authors evaluated the roles of auditory-verbal short-term memory, visual short-term memory, and group membership in predicting language comprehension, as measured by an experimental sentence comprehension task (SCT) and the Test for Auditory Comprehension of Language--Third Edition (TACL-3; E. Carrow-Woolfolk, 1999) in 38 participants: 19 with Down syndrome (DS), age 12 to 21 years, and 19 typically developing (TD) children, age 3 to 5 years, matched on syntax comprehension, as measured by TACL-3 Subtests II and III. Of the 5 dependent measures of comprehension, auditory-verbal short-term memory accounted for significant amounts of variance in 4; group membership, 1 (semantic role assignment); and visual short-term memory, 0. In the group with DS, hearing status predicted variation in Grammatical Morphemes (TACL-3 Subtest II). Using the SCT, the authors also investigated the effects of varying sentence voice and supporting visual context on sentence comprehension. SCT performance was significantly poorer in terms of (a) referent selection and semantic role assignment, for passive (vs. active) sentences in both groups, and (b) semantic role assignment in all sentences for the group with DS (vs. the TD group). Vocabulary strengths in the group with DS were found with the Peabody Picture Vocabulary Test--Third Edition (L. M. Dunn & L. M. Dunn, 1997) but not the TACL-3 Vocabulary subtest.