Reading Working Papers in Linguistics 4 (2000) - The University of ...

LEXICAL AND GRAMMATICAL DEFICITS IN SLI
acquisition of words and utterance chunks constituting a major part of a
child’s acquisition of language in the first year and a half of life. They are
items with phonological and semantic representations and they are stored in
long term memory. Locke quotes Thal, Tobias and Morrison (1991) who
found an association between small receptive vocabulary and language
progress more generally, in support of his notion that it is delayed receptive
vocabulary which in some way leads to grammatical deficit. A second
important strand in his argument was that he accepted the 'constant lag' claim
of Bishop and Edmundson (1987): the finding that children with serious
language delays surveyed over an 18 month period made progress in language
comparable with the rate of acquisition of their language-normal peers, even
though they had experienced an initial delay and thus continued to lag behind
them in language development. As observed by Leonard (1998) and others,
Locke’s ideas are challenging but call for empirical investigation.
If one wishes to investigate Locke’s proposals empirically, the direct
route is to compare children with and without a receptive lexical deficit and
try to discover what effects this factor might have on their grammatical
development. Ideally one would like to pursue a longitudinal study to check
the assumption made by Locke of a constant lag; this is how he refers to
Bishop’s findings that, measured against LN children, children with SLI make
18 months’ worth of progress in 18 months of time. Clearly lexical
development is unlikely to be totally uniform; we know that most children
show a lexical spurt in the second year of life, so we can’t rule out other such
spurts. But the research reported here was not in a position to check this
assumption, so it will be assumed with Locke that SLI children’s lexical
deficits arise from a late start and not or not primarily from a lower rate of
lexical acquisition. The general issue raised in this study was whether, as
claimed by Locke (1994, 1997), grammatical SLI is a result of poor lexical
assimilation in the early years of language acquisition. Locke’s (1997:282)
striking formulation of this position is ‘A lexicon delayed may be a grammar
denied.’
The research question addressed in this paper is: What kind of evidence
can be brought to bear on the proposed relationship between grammar and
lexicon within a particular population, such as children with SLI? This work
in progress paper report the findings of an exploratory study conducted with a
group of children with SLI intended to throw some light on this issue.
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