Language Phenotypes

Abstract

Language is a complex, uniquely human capacity. At birth, infants are prepared to acquire language, which develops over time with most of the essential elements in place by the time a child enters school. In this chapter, we focus our attention on language phenotypes that have shown significant promise in current research on developmental language disorders and that are grounded in what is known about typical language acquisition. This line of research not only is important for advancing our understanding about the underlying etiology of these disorders, which can have lasting impact on the lives of the children, but also holds the potential for discovering the genetic bases of language, the most remarkable achievement of human evolution. Early work on the search for language genes associated with language disorder focused on the investigations of the famous KE family in which about half of the family members suffered severe language, but not cognitive, impairments. But this research was hampered by researchers' failure to cast a broad net in their characterization of the full phenotype of the affected individuals. Thus, when mutations in the F0XP2 gene were discovered as the basis of the KE family syndrome, initial reactions were that this was the "grammar gene." We now know that the phenotype of the F0XP2 syndrome includes not only grammar, but also motor and phonological features of language. The lessons learned from this work are that studies of language phenotypes need to encompass measures that tap multiple language domains and that are developmentally sensitive. (PsycINFO Database Record (c) 2017 APA, all rights reserved)