ABSTRACT
Mabel Rice and Ken Wexler present theory and preliminary data on a clearly interesting developmental phenomenon and a potentially useful language impairment phenotype, the extended optional infinitive (EOI). As noted in their chapter, and in other chapters throughout this book, accurate characterization of an SLI phenotype is critical for future genetic work. All too often research has relied on omnibus language tests with little or no theoretical basis. Moreover, it has been common practice to use qualitative diagnoses that are based on relatively arbitrary cutoffs. Both omnibus tests and qualitative diagnoses can result in a “noisy” phenotype and lead to erroneous conclusions regarding the genetics for a disorder, such as SLI.
