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A May 2002 Merrill Conference, "The Relationship of Genes, Environments, and Developmental Language Disorders: Research for the 21st Century," provided an important initial step in bringing together a small group of interdisciplinary scholars to discuss the current state of research in the genetics of language disorders. Broad research needs were identified. A follow-up workshop, cosponsored by the Merrill Advanced Studies Center of the University of Kansas and the National Institute of Child Health and Human Development, focused on the steps necessary to address those research needs and identified limitations to implementing future research.
The investigation of the genetic bases of language and language disorders will require clear delineation of behavioral phenotypes, identification of neurocognitive substrates, synthesis of emerging discoveries across different clinical diagnoses (e.g., Williams syndrome, fragile X, autism, specific language impairment), new models of genetic mechanisms, new methods of gene discovery, and new quantitative techniques for estimation of genetic effects and effect sizes. Despite progress that continues to be made in this important area, there are factors that impede the research: distributed sources of funding, traditional disciplinary boundaries, and insufficient communication networks among scientists.
In the September 2003 workshop and McCardle and Cooper (2004), four major issues were outlined that are crucial to moving forward in the area of language and genetics.
THE FOUR ISSUES
There must be recognition of the continuum of language behaviors
We must not lose sight of the fact that language abilities fall along a continuum from typical language development, observable in monolingual and bilingual children and deaf children of deaf parents, through the spectrum of children with language impairments, whether related to specific syndromes or as-yet unknown etiologies. Although language impairments vary in timing and severity, for most groups of children they seem to fall along a developmental continuum, showing slowed, arrested, or regressed development, but not showing characteristics that are totally foreign to what we know of some period of typical language development. Thus, as we seek clues to the role of genetics in language development and its disorders we must be both "lumpers" and "splitters" as we seek to define narrow behavioral phenotypes and to develop and test interventions. That is, not only must we combine and look across groups to capture what is general or common,...