ABSTRACT
This chapter considers whether two measures that had their origins in the study of normal language development, one based on utterance length and the other on lexical diversity, can be used to differentiate children with and without Specific Language Impairment (SLI). It also critically examines the usefulness of these and other measures as potential clinical markers of SLI. Younger, typically developing children and children with SLI tend to use the errors exemplified in sentences 1b–5b inconsistently, interspersed with correct productions, in both conversational speech and elicited probes. Researchers have begun to acknowledge that simply showing that there are significant differences between children with and without SLI on a particular linguistic or processing feature is insufficient for demonstrating the presence of a marker. Children with SLI differ from typically developing children in terms of the average length of their spoken utterances, their lexical development, and their deployment of specific grammatical morphemes.
