Effects of sampling context on spontaneous expressive language in males with fragile X syndrome or Down syndrome.

PURPOSE In this study, the authors examined the impact of sampling context on multiple aspects of expressive language in male participants with fragile X syndrome in comparison to male participants with Down syndrome or typical development. METHOD Participants with fragile X syndrome ( n = 27), ages 10-17 years, were matched groupwise on nonverbal mental age to adolescents with Down syndrome ( n = 15) and typically developing 3- to 6-year-olds ( n = 15). Language sampling contexts were an interview-style conversation and narration of a wordless book, with scripted examiner behavior. Language was assessed in terms of amount of talk, mean length of communication unit (MLCU), lexical diversity, fluency, and intelligibility. RESULTS Participants with fragile X syndrome had lower MLCU and lexical diversity than did participants with typical development. Participants with Down syndrome produced yet lower MLCU. A differential effect of context among those with fragile X syndrome, Down syndrome, and typical development emerged for the number of attempts per minute, MLCU, and fluency. For participants with fragile X syndrome, autism symptom severity related to the number of utterances produced in conversation. Aspects of examiner behavior related to participant performance. CONCLUSION Sampling context characteristics should be considered when assessing expressive language in individuals with neurodevelopmental disabilities.