Purpose: Researchers have previously shown that individual differences in measures of receptive language ability at age 12 are highly heritable. In the current study, the authors attempted to identify some of the genes responsible for the heritability of receptive language ability using a "genome-wide association" approach. Method: The…

Purpose: Behavioral genetic studies of speech fluency have focused on participants who present with clinical stuttering. Knowledge about genetic influences on the development and regulation of normal speech fluency is limited. The primary aims of this study were to identify the heritability of stuttering and high nonfluency and to assess the…

A case-control family study design examined the current language-related abilities of all biological, primary relatives of probands (N=22) with specific language impairment (SLI) and of matched controls. Impairment rates for family members of SLI probands was significantly higher than for controls. Also, impairment rates estimated from a family…

Immediate and extended families of 66 stuttering children were investigated to determine frequencies of persistent and recovered stuttering. Recovery was far more common among females than males. Recovery or persistence was found to be transmitted, but the two types are not genetically independent, consistent with hypothesis that both forms share…

To examine the basis of familiar associations with poor language achievement, 62 twin pairs and 3 triplet sets were studied in which at least one member presented poor oral-language status in the absence of other impairments. The language status of monozygotic pairs was highly similar. (Author/CR)

A study involving 55 children with a language impairment and 76 with normal language investigated the heritability of auditory processing impairment in same-sex twins (ages 7 to 13, selected from a sample of 37 pairs). Although correlations between co-twins were high, lack of significant difference between monozygotic and dizygotic twins suggested…

A study examined family histories of 31 children with specific language impairments who were known to have particular grammatical limitations in a core feature of grammatical acquisition, a stage known as Extended Optional Infinitives. The families had significantly more speech and language difficulties, as well as language-related difficulties,…

Two family aggregation studies involving 25 children (ages 5-10) with specific language impairment (SLI) report the occurrence and co-occurrence of oral language impairments and reading impairments. Results indicate that when language impairments occur within families of SLI probands, these impairments generally co-occur with reading impairments.…

A study investigated 136 toddlers from 112 families with or without a history of specific language impairment (SLI). SLI was found to aggregate in families; the average rate in families affected with a family history of SLI was 32%, with significantly more boys reported as having SLI than girls. (Contains references.) (Author/CR)

This study of 4,274 pairs of 4-year-old twins from the Twins Early Development Study explored the magnitude of genetic and environmental effects on low expressive vocabulary skill, both as a function of general cognitive ability and as a function of the severity of expressive vocabulary impairment. Assessments were conducted through parent report…

A study involving 356 twin pairs with early language delay found environmental influences shared by both twins were more substantial than genetic factors. Heritability was significantly higher in those with persisting difficulties but only when assessed in terms of parental concern at 3 years or professional involvement at 4 years. (Contains…