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

LEXICAL AND GRAMMATICAL DEFICITS IN SLI
There was no significant difference in the performance of the two SLI groups
distinguished by the presence or absence of a lexical deficit. Wilcoxon rank
sums test: z = -7.56 n.s
The findings so far indicated that a pronounced lexical deficit predicts
neither a grammatical problem on a common measure of morphological
impairment, nor poor performance on a measure of verb argument structure
devised by earlier research showing that children with SLI often had a deficit
in this area. The position taken in Locke (1994, 1997) that the lexical
acquisition mechanism is responsible for grammatical impairment has not
been upheld. It even appears that poor receptive lexical knowledge does not
account for delayed verb argument structure acquisition, which is more
surprising since one might well think of argument structure as subserved by a
lexical acquisition mechanism.
This finding prompted a further question: was verb argument structure
ability associated with grammatical ability? To investigate this question,
scores on past tense production were compared with scores on argument
structure alternations. To permit group comparisons, each SLI child was recategorised
for this purpose as + or – Grammatical Deficit (GD) on the
strength of the past tense production task. Nine children with a production
rate of under 60% were categorised as GD, the other 11 as NGD. Because of
the lack of association between grammatical deficits and lexical deficits
remarked on earlier, some children with SLI in the GD group had a lexical
deficit, while others did not, and the same was the case for the [-GD] group.
Table 3: Mean no. of argument structure alternations(Max N = 5)
SLIs [+GD]
LN MATCHES of SLIs [+GD]
MEAN 1.11 2.89
Wilcoxon’s T = 1.5 (N=9) p = 0.5, 2-tailed
SLIs [-GD]
LN MATCHES of SLIs [-GD]
MEAN 3.00 2.64
Wilcoxon’s T = 33.0 (N=11) n.s., 2-tailed
This analysis showed a clear difference in the argument structure performance
of the children with SLI grouped by grammatical deficit. Statistical analysis
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