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Causal Pathways for Specific Language Impairment: Lessons from Studies of Twins
- Source :
-
Journal of Speech, Language, and Hearing Research . Oct 2020 63(10):3224-3235. - Publication Year :
- 2020
-
Abstract
- Purpose: This review article summarizes a program of longitudinal investigation of twins' language acquisition with a focus on causal pathways for specific language impairment (SLI) and nonspecific language impairment in children at 4 and 6 years with known history at 2 years. Method: The context of the overview is established by legacy scientific papers in genetics, language, and SLI. Five recent studies of twins are summarized, from 2 to 16 years of age, with a longitudinal perspective of heritability over multiple speech, language, and cognitive phenotypes. Results: Replicated moderate-to-high heritability is reported across ages, phenotypes, full population estimates, and estimates for clinical groups. Key outcomes are documentation of a twinning effect of risk for late language acquisition in twins that persists through 6 years of age, greater for monozygotic than dizygotic twins (although zygosity effects disappear at 6 years); heritability is greater for grammar and morphosyntax than other linguistic dimensions, from age 2 years through age 16 years, replicated within twin samples at subsequent age levels and across twin samples at age 16 years. Conclusion: There is consistent support for legacy models of genetic influences on language acquisition, updated with a more precise growth signaling disruption model supported by twin data, as well as singleton data of children with SLI and nonspecific language impairment.
Details
- Language :
- English
- ISSN :
- 1092-4388
- Volume :
- 63
- Issue :
- 10
- Database :
- ERIC
- Journal :
- Journal of Speech, Language, and Hearing Research
- Publication Type :
- Academic Journal
- Accession number :
- EJ1281112
- Document Type :
- Journal Articles<br />Reports - Research
- Full Text :
- https://doi.org/10.1044/2020_JSLHR-20-00169