It has been claimed that the development of language in children with Down syndrome is but a slow-motion replica of the normal course of acquisition, identical in all respects but rate of acquisition (Lenneberg, 1967). Despite delays in the onset and timing of language development, the language structures that are acquired by children with Down syndrome have consistently been described as normal and unremarkable in the order of their appearance. In the speech of children with Down syndrome, there has been no evidence of deviant forms or constructions not observed at some stage of normal development (Bloom & Lahey, 1978; Evans & Hampson, 1968; Rondal, 1975; Rosenberg, 1982; Ryan, 1975).

Our discussion does not challenge the standard view of Down syndrome language as “delayed without deviance.” How it differs is by shifting attention away from the issue of deviance (or lack thereof) to focus upon substantial, unexplained delays in acquiring language structure. In particular, this chapter covers two robust features of Down syndrome language that have previously drawn little attention, but which call for an explanation. The first is that the ultimate syntactic and morphological levels achieved by most individuals with Down syndrome are consistently low across a number of studies, independent of assessment procedures. The second is that this limited language development cannot be explained as a simple function of general intellectual development, or as a function of more general verbal or communicative skill (see Beeghly, Weiss-Perry, & Cicchetti, Chapter 10, this volume). In making these points, the evidence for a specific syntactic deficit is examined, and it is asked whether particular areas within syntax or morphology pose special difficulties for the child with Down syndrome.