Sentence imitation by adolescents and young adults with Down's syndrome and other intellectual disabilities.

Sentence imitation performance was evaluated longitudinally in 26 adolescents and young adults with Down's syndrome (DS), and 26 age- and IQ-matched non-DS individuals with other causes of intellectual disability (ID). In each of three annual assessments, the DS group began sentence repetitions more slowly and imitated sentences less accurately than the ID group. DS sentence repetition accuracy was equivalent to the ID group only for two-word sentences and was poorer for every other sentence length. Comparisons of sentence imitation and auditory digit span scores suggested that only ID subjects benefitted from the additional meaning and structure provided by sentences. Correlational analyses performed between each year's sentence imitation score and a set of language, memory and hearing measures revealed that sentence imitation was related to grammatical comprehension, auditory short-term memory and IQ in both groups, and to expressive language ability, speed of spoken word processing, speech discrimination and acoustic reflexes in the DS group only. A significant relationship between sentence imitation and middle-ear functioning was further supported by a categorical analysis in which DS subjects with bilateral abnormal tympanograms tended to perform more poorly on sentence imitation tasks than DS subjects with at least one normal tympanogram. It was concluded that sentence imitation is a task that is sensitive to the auditory-perceptual, cognitive and expressive difficulties evidenced by individuals with DS.