Genetics & Language Development

[Andre Cramblit]

Genetics Influence Adolescent Language Problems
http://www.sciencedaily.com/releases/2005/05/050517063228.htm

Specific language impairment (SLI) is a condition in which a child’s  
language development is deficient despite showing normal development  
in all other areas. New research, published in Current Directions in  
Psychological Science, attempts to identify the cause behind this  
affliction.

Factors such as poor parenting, subtle brain damage or hearing loss  
have previously been regarded as the cause behind SLI. The findings  
indicate, however, that these factors are far less important than  
genetics, specifically, an unidentified combination of defective  
genes, when determining risk and that no single cause can account for  
all cases.

“As a greater understanding of the issues and their causes becomes  
apparent, more effective interventions can be devised; tailoring  
treatments to an individual child’s specific, underlying problems,”  
says Dr. Dorothy Bishop, author of the study.

Research into this condition is helping scientists unravel the  
mystery behind how genetics contribute to the development of language.

Genetic Factors Partly Influence Differences In Language Development

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, was published in the May/June issue of the journal Child  
Development.

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, she notes, 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.

"The results are similar when only the low end of language ability is  
studied, with the possible exception of the two receptive measures,"  
she said. "This similarity is consistent with the hypothesis that the  
same genetic and environmental influences are involved in shaping  
individual differences and differences in risk of a language-related  
disorder. If this turns out to be the case, it means that when genes  
and specific aspects of environments that affect language disability  
are discovered, they will be also involved in individual differences  
in language ability."

Study results also suggest that the same genes and environments  
similarly affect individual differences in the language ability of  
boys and girls.

"Establishing the role of genetic influences in diverse aspects of  
language is only a first step in providing a foundation and a  
motivation for molecular genetic studies to find the multiple  
specific genes involved," said Kovas. "Similarly, establishing the  
relative importance of environmental influences is just a first step  
toward future research to identify specific environments involved. As  
specific genes and environments are identified, we can begin to  
understand the complex mechanisms of development of individual  
differences in language abilities."
###

Summarized from Child Development, Vol. 76, Issue 3, Genetic  
influences in different aspects of language development: The etiology  
of language skills in 4.5 year-old twins by Kovas Y, Hayiou-Thomas  
ME, Oliver B (Institute of Psychiatry), Dale PS (University of  
Oxford), Bishop DVM (University of Missouri-Columbia), and Plomin R  
(Institute of Psychiatry). Copyright 2005 The Society for Research in  
Child Development, Inc. All rights reserved.