ABSTRACT
The aim of this book is to look at the ways in which evidence from different populations can provide insights into the theory of language acquisition. The population discussed in this chapter is children who have specific problems with the acquisition of language but who are otherwise unimpaired. In particular, the chapter will present data from a large family that exhibits a specific language disorder. There is evidence that this developmental disorder has a genetic etiology associated with an autosomally dominant gene. This evidence will be used to discuss both the way in which linguistic theory influences the characterization of this disorder and the way in which the existence of this genetic language disorder has consequences for the metatheoretical properties of language. This disorder constitutes a natural experiment that can provide direct evidence about the heritability of language. Fundamental assumptions about language provided by theories of language and theories of the acquisition of language necessary for any serious characterization of this disorder are presented. It is shown that present accounts of specific language impairment often ignore these fundamental linguistic principles and therefore misinterpret some aspects of the problem. In addition, the significance of this genetic disorder for metatheoretic issues such as innateness, species specificity, and modularity are discussed.
