Basic numeracy in children with specific language impairment: heterogeneity and connections to language.

PURPOSE: This study examined basic numerical skills in children with specific language impairment (SLI) and how well linguistic factors explain the variance in these children's number skills. METHOD: The performance of children with SLI (n=29) was compared with that of typically developing children along a continuum ranging from preschool to 3rd grade (n=20, 47, 40, and 33). This facilitated both linguistic and educational age comparisons. To study number skills within the SLI group more closely, this group was divided into subgroups on the basis of their performance in verbal and nonverbal numerical skills. The performance of the different SLI subgroups on the linguistic and nonverbal reasoning task was analyzed. RESULTS: As a single group, the children with SLI lagged behind their educational age controls in both verbal and nonverbal numerical skills. Subgroup analyses revealed that the ability to retrieve arithmetic facts from the memory was connected to naming fluency, whereas the differences in nonverbal numerical skills were not explained by the cognitive skills measured (nonverbal reasoning skill, verbal short-term memory, vocabulary, comprehension, and naming fluency). CONCLUSIONS: This study demonstrates that children with SLI form a very heterogeneous group in their numerical skills, and thus specific hypotheses concerning the influence of linguistic deficits on developing numerical skills are required. The cognitive components of serial naming speed present a promising domain for further exploration.