This study was designed to establish the extent of delay in complex sentence use by females with fragile X syndrome (FXS) and to identify sources of variability among individuals. Females with FXS (n = 16; 10;2-15;7) and younger typically developing girls (n = 17; 4;1-8;11) were group-wise matched on nonverbal cognition and receptive syntax. Language samples (conversation and narration) yielded syntactic complexity in terms of mean length of C-unit (MLCU) and Developmental Level sentence coding (DLevel; Rosenberg & Abbeduto, 1987 ). Complex syntax was not weaker than developmental expectations; however, MLCU was lower than expected for age. Phonological memory and verbal working memory correlated with measures of syntactic complexity in narration. Discourse demands may play an important role in the language produced by females with FXS.
Keywords: expressive language; individual differences; short-term memory; working memory.