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

LEXICAL AND GRAMMATICAL DEFICITS IN SLI
All the matches scored above 85%, but five of the SLIs in the [+LD] group
and four of those in [-LD] group (Figure 2) scored below 60%. The means for
the two SLI groups are almost identical, close to 63%:
Table 2: Group mean percent correct on reg. Past Tense realisation
SLI [+LD] Past Tns
LN matches of [+LD]s
63.4 95.5
63.5
SLI [-LD]
matches of [-LD]s
62.5 98.0
The lexical deficit clearly fails to predict performance on regular past tense,
considered to be a key indicator of grammatical deficit. The implications of
this finding will be discussed below.
Other vulnerable areas of grammar in grammatical impairment (Loeb &
Leonard 1991) are null subjects and pronoun case. Even adults sometimes
ellipt subjects in finite clauses (cf. Schelletter 1990), so a null subject score of
up to 5% was not taken as an indicator of a grammatical deficit. However,
only two of the SLI children with a LD showed null subjects with a frequency
of over 5% and with the SLI children with no lexical deficit the same was
found. Pronoun case errors, where a child used the object form of a pronoun
in a nominative case context were rare in both SLI groups.
Thus the hypothesis derived from Locke that the [+LD] children with
SLI would show a pattern of much more severe grammatical deficits than the
[–LD] group was not upheld. What we found instead is a dissociation
between widespread problems with past tense forms, and generally correct
performance on pronoun forms and obligatory subjects, a result which in fact
raises questions as to the account of grammatical SLI as an extended optional
infinitive phase (Rice, Wexler & Cleave 1995) which cannot be pursued here
for reasons of space. However, it should be noted that the four children with
frequent null subjects were among those with the lowest past tense realisation,
an association predicted by the optional infinitive account.
We move on now to the other issue that investigated in this research.
Was verb argument structure performance associated with a lexical deficit? In
order to answer this question, rather than comparing SLI groups with their
matches, we need to compare the performance of the two SLI groups directly.
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