Examining the Language Phenotype in Children With Typical Development, Specific Language Impairment, and Fragile X Syndrome.

Purpose: One aspect of morphosyntax, finiteness marking, was compared in children with fragile X syndrome (FXS), specific language impairment (SLI), and typical development matched on mean length of utterance (MLU). Method: Nineteen children with typical development (mean age = 3.3 years), 20 children with SLI (mean age = 4.9 years), and 17 boys with FXS (mean age = 11.9 years) completed the Test of Early Grammatical Impairment (TEGI; Rice & Wexler, 2001), and other cognitive and language assessments. Quantitative comparisons on finiteness marking and qualitative comparisons of unscorable (i.e., nontarget) TEGI responses were conducted.
Results: Children with typical development and FXS performed better on finiteness marking than children with SLI. Although unscorable responses were infrequent, boys with FXS produced more unscorable responses than children with typical development and SLI. Conclusions: Although boys with FXS have language deficits, they performed similarly to MLU-matched typically developing children on finiteness marking. This language profile differs from children with SLI, who present with a delay-within-a-delay profile with finiteness marking delays that exceed delays in MLU. Unscorable responses produced by the boys with FXS may reflect pragmatic deficits, which are prominent in this population. Assessment procedures should be carefully considered when examining language in boys with FXS.