This epidemiologic study estimated the prevalence of specific language impairment (SLI) in monolingual English-speaking kindergarten children. From a stratified cluster sample in rural, urban, and suburban areas in the upper midwest, 7,218 children were screened. The language screening failure rate was 26.2%. Children who failed the screening and a similar number of controls were then administered a diagnostic battery (n = 2,084) that provided for a diagnosis of SLI using common diagnostic standards. Results provided an estimated overall prevalence rate of 7.4%. The prevalence estimate for boys was 8% and for girls 6%. Variation in prevalence was found among children of different racial/cultural backgrounds; however, these background variables were found to be correlated with parental education, which was also associated with SLI. The parents of 29% of the children identified as SLI reported they had previously been informed that their child had a speech or language problem.The prevalence estimates obtained fell within recent estimates for SLI, but demonstrated that this condition is more prevalent among females than has been previously reported. Also, the clinical identification of these children remains low among kindergarteners.

This study examined nonword repetition performance in a population-based sample of school-age children. A total of 581 second graders who were participating in a longitudinal, epidemiologic investigation of specific language impairment (SLI) were administered the Nonword Repetition Task (NRT) developed by Dollaghan & Campbell (1998). Performance was examined according to second-grade diagnostic category, presence/absence of language impairment, and treatment status. Results indicated that children with language impairment, as well as those in intervention, exhibited deficient nonword repetition skills compared to normal language controls. Findings also confirmed that the NRT is a culturally nonbiased measure of language processing. Results from likelihood ratio analyses indicated that NRT performance, though not sufficient on its own, may provide a useful index to assist in ruling in or ruling out language disorder.

Children with language impairment (LI) have been shown to be at risk for reading disability (RD) and behavior disorder (BD). Previous research has not determined the specific pattern of these conditions associated with LI. This study sought to determine if the behavior disorder and reading problems represented different outcomes or if these conditions occurred together when found with LI. A group of 581 second-grade children, including 164 children with LI, were examined for spoken language, reading, and behavior disorder. The data for each of these areas were examined as dimensional traits and as clinical categorical traits. Reading and spoken language were found to be strongly correlated (r = .68); RD was found in 52 % of the children with LI and in only 9 % of the controls. Scores of parent ratings for BD were also significantly correlated with spoken language scores (r = .29). Clinical levels of BD were found in 29% of the children with LI and 19% of the controls. An examination of the co-occurrence of clinical levels of BD, RD, and LI showed BD in children with LI to be conditioned by the child's reading status. The data indicated that whereas RD was directly associated with BD, the association of LI with BD required the mediation of RD.

In order to examine the basis of familial associations with poor language achievement, 62 twinship pairs and 3 sets of triplets were studied in which at least one member presented poor oral language status in the absence of other developmental or sensory impairments. Rates of concordance for poor language were compared between the monozygotic (MZ) and dizygotic (DZ) pairs. Concordance for the MZ pairs was .96, whereas it was .69 for the DZ pairs. The DeFries-Fulker method for computing heritability of extreme scores was employed yielding a h2g of .45. Similar results were obtained for those pairs containing only children with performance IQs above 85, but with at least one member having language below -1 SD. A comparison of DZ twins with singleton sibling pairs with at least one affected member and of similar age showed that DZ twins were more similar with respect to language achievement than singleton pairs. Thus, twinning appeared to have influenced twin resemblance among those where at least one member presented poor language achievement. These results support the hypothesis that genetic factors contribute to the liability of poor language achievement in children who do not present other developmental or sensory disorders.

Children with language impairment (LI) have been shown to be at risk for reading disability (RD) and behavior disorder (BD). Previous research has not determined the specific pattern of these conditions associated with LI. This study sought to determine if the behavior disorder and reading problems represented different outcomes or if these conditions occurred together when found with LI. A group of 581 second-grade children, including 164 children with LI, were examined for spoken language, reading, and behavior disorder. The data for each of these areas were examined as dimensional traits and as clinical categorical traits. Reading and spoken language were found to be strongly correlated (r = .68); RD was found in 52 % of the children with LI and in only 9 % of the controls. Scores of parent ratings for BD were also significantly correlated with spoken language scores (r = .29). Clinical levels of BD were found in 29% of the children with LI and 19% of the controls. An examination of the co-occurrence of clinical levels of BD, RD, and LI showed BD in children with LI to be conditioned by the child's reading status. The data indicated that whereas RD was directly associated with BD, the association of LI with BD required the mediation of RD.