Genetic factors appear to influence individual differences in language development among children, at least in part, according to a study by British and American researchers. The study, which also found that environmental influences on children's language development were unique to the individual, not the shared environment
Researchers from the Institute of Psychiatry in London, the University of Oxford, and the University of Missouri-Columbia in the United States investigated both individual differences in language development in the normal range and at the low end of ability in 4 1/2-year-old twins.
They recruited participants as part of the Twins Early Development study (TEDS), a longitudinal study involving a representative sample of all twins born in England and Wales in 1994, 1995 and 1996. It is the largest twin study to investigate diverse aspects of language, including articulation, phonology, grammar, vocabulary and verbal memory in a group of children of the same age. Opposite-sex twins were included in the study in order to explore sex differences in genetic and environmental influences for each individual measure.
"Children differ in the rates in which they acquire language and in their linguistic ability," explained lead researcher Yulia Kovas, a PhD student at the Institute of Psychiatry in London. "Understanding the sources of this variation is an important part of forming a comprehensive account of language development."
The study findings are consistent with previous research showing that differences between children in different aspects of language development do not seem to be uniquely dependent on genes or environment.
Study results also suggest that the same genes and environments similarly affect individual differences in the language ability of boys and girls.