Pioneering work by Ursula Bellugi and her colleagues in the late 80's suggested that Williams Syndrome (WS) provides strong evidence for the modularity of language. This naturally-occurring genetic disorder results in mild to moderate levels of retardation, but supposedly "intact" language.
Work over the past decade has challenged both the notion that language is entirely intact in WS, and even the weaker claim that if not perfect, it at least outstrips overall cognitive level. Some researchers have thus concluded that WS does not provide evidence for language modularity. Additional results have convinced some researchers that WS children may acquire language in a fundamentally different way from unimpaired children--relying perhaps on their good auditory verbal memory skills. If true, this would suggest that the WS cannot teach us anything about normal processes of acquisition.
I challenge both of these conclusions in light of both arguments and results from a variety of elicited production studies with a group often WS children (age 10-16) and ten unimpaired children matched for mental age (age 4-7), as well as preliminary data from adults with WS.
The results demonstrate that the kinds of structures WS children are capable
of generating are extremely impressive and cannot be explained by appealing
to good auditory verbal memory. The results also demonstrate that WS children
make developmentally normal errors, while failing to make odd errors which would
likely be expected if WS involves abnormal acquisition mechanisms. However,
WS people tend to make MORE developmentally normal errors than unimpaired children
of the same mental age, and these errors are longer lasting--indeed some errors
persist into adulthood. This kind of finding may explain why some researchers
believe that WS provides no special evidence for language modularity, but I
argue that while language is not perfect in WS, it nevertheless represents one
extreme end of a continuum of language outcomes for groups with comparable retardation,
and thus it provides a subset of the data showing that cognitive impairments
do not straightforwardly predict language impairments.
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