ABSTRACT
The twin method has been used to test several questions regarding the nature of specific language impairment (SLI). To begin with, the hypothesis that specific language disorders are genetically influenced has been tested using the twin design. Children who have more limited opportunities to have access to spoken language are less likely to fare well in language learning. A discussion of the molecular genetics of developmental language disorders needs to begin with one gene, the FOXP2 gene, which has been associated with developmental speech and language impairment. The findings from the SLI consortium linkage studies have provided indications that gene variation linked to poor language and in particular the endophenotype of phonological memory might be found in the SLI1 region of chromosome 16. Delays in language onset and development are an important diagnostic feature of autism spectrum disorder, along with repetitive behaviors and poor social skills.
