Against the background of a broad range of language features that are identified as characteristic of specific language impairment (SLI), some researchers have identified a narrower set of clinical markers considered the hallmark of SLI. However, comparisons with language impairments that fall outside the criteria for SLI are limited. This thesis is concerned with determining which language features, if any, are capable of differentiating children with SLI from children with non-specific language impairment (NLI).
Conversation and oral narrative language samples were collected from seventy five children aged 2 ½ to 6 years comprising four research groups: 21 participants with SLI, 13 participants with NLI, 21 age-matched participants with normally developing language (AM) and 20 younger language-matched participants with normally developing language (LM). Matching for group comparisons required that the SLI and NLI groups had similar levels of language ability on a standardised assessment and mean length of utterance (MLU), which reduced the SLI group to 15 participants for these comparisons. The LM group was also matched to the SLI and NLI groups on MLU. A wide range of language variables from the conversation and narrative samples were analysed, covering the domains of general sample measures, morphosyntactic accuracy and complexity, narrative structure and cohesion.
The SLI and NLI groups performed similarly in all domains and could not be differentiated diagnostically on the measures examined. The most consistent group effects were for comparisons between the AM and LM groups, which demonstrated the effects of maturation and development. The language impairment (LI) and LM groups could not be differentiated on the majority of general language sample or morphosyntactic measures but the SLI group produced narratives that were structurally more complex and cohesive than the LM group.
Language tasks varied in their effectiveness in differentiating groups. More consistent group effects for the grammatical accuracy measures were obtained from the conversations than the narratives, and from composite measures compared to individual morpheme measures. Targeted elicitation tasks were more effective than the conversations or narratives in producing consistent group effects for accuracy of individual verb tense morphemes. More consistent group effects for the narrative features were obtained from a wordless picture book than a single scene picture. A set of discriminant function analyses showed that LI was most effectively identified using a combination of key morphosyntactic measures from the conversations and key narrative feature measures from the two narratives.
The results have implications for diagnostic practices, intervention practices and theoretical constructs and explanations of SLI and NLI. In particular, a broad, holistic view of LI is supported, as an impairment that impacts on all domains of language which interact with each other and must be considered collectively, rather than as individual, splintered skills.
| Identifer | oai:union.ndltd.org:ADTP/216424 |
| Date | January 2007 |
| Creators | Pearce, Wendy Maureen, wendy.pearce@jcu.edu.au |
| Publisher | Flinders University. Medicine (Dept of Speech Pathology & Audiology) |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://www.flinders.edu.au/disclaimer/), Copyright Wendy Maureen Pearce |
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