Abstract

The papers in this issue present a series of comparative studies of language processing and language development across clinical populations, including studies in the earliest stages of language development, as well as aspects of grammar, narrative, and verbal memory across the elementary school years. The populations covered include ‘‘late talkers,’ ’ children with congenital injuries to either the left or right hemisphere, children with Williams Syndrome, children with Down Syndrome, children with a diagnosis of specific language impairment (behaviorally defined), and a range of typically developing controls for each of these groups. As Holland points out in her commentary, two of the most surprising findings across these studies include the following. (1) Despite differences in rate of development, the sequences and error types observed are (with a few interesting exceptions) remarkably similar across these very different clinical groups. It appears that sequences and error types are determined primarily by the ‘‘problem space’ ’ posed by a particular language (in this case English), so that virtually all children who enter into this problem space end up behaving in much the same way, albeit at variable rates. Reilly et al. (this issue) suggest a metaphor for results like these: all of these children have undertaken a journey along the same highway, but some of them are in the slow lane, with occasional stops along the road. (2) Children with well-defined brain injuries of the kind that often lead to aphasia in adults perform within the normal range on most measures once they move into the elementary school years, with no trace of a selective disadvantage for children with left-hemisphere damage

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