Genetic Influences in Different Aspects of Language Development: The Etiology of Language Skills in 4.5-Year-Old Twins


  • We gratefully acknowledge the ongoing contribution of the parents and children in the Twins' Early Development Study (TEDS). TEDS is supported by a program grant (G9424799) from the UK Medical Research Council.

concerning this article should be addressed to Yulia Kovas, Social, Genetic, and Developmental Psychiatry Centre, Institute of Psychiatry, De Crespigny Park, London, England SE5 8AF. Electronic mail may be sent to


The genetic and environmental etiologies of diverse aspects of language ability and disability, including articulation, phonology, grammar, vocabulary, and verbal memory, were investigated in a U.K. sample of 787 pairs of 4.5-year-old same-sex and opposite-sex twins. Moderate genetic influence was found for all aspects of language in the normal range. A similar pattern was found at the low end of the distribution with the exception of two receptive measures. Environmental influence was mainly due to nonshared factors, unique to the individual, with little influence from shared environment for most measures. Genetic and environmental influences on language ability and disability are quantitatively and qualitatively similar for males and females.