| Summary: | There has been limited investigation into the nature of specific language
impairment (SLI) in adolescence, and even less investigation into speech
production in SLI, particularly beyond the preschool years. Phonological output
is crucial to oral expressive language, one of the characteristic areas of deficit in
SLI. It was hypothesized that adolescents with SLI present with residual speech
errors. Accordingly, this study investigated the presence, nature and cause of
speech deficits in adolescents with persistent SLI.
Adolescents aged 13.0-14.0 years with persistent SLI (n=31) were
compared to typically developing (TD) peers (n=31) on an Oral Motor Evaluation
(OME) and a Speech Assessment Battery (SAB), consisting of: Multisyllabic
Word Repetition, Nonsense Word Repetition, Phrase Repetition, Sentence
Repetition and Tongue Twisters. Tasks were analysed in terms of accuracy and
the amount of effort required, to determine efficiency and automaticity of
phonological output. All participants completed a battery of memory tasks and
the language abilities of the SLI group were evaluated. Caregivers completed
questionnaires investigating risk factors.
Results indicated that adolescents with persistent SLI produced a higher
number of inconsistent and context-dependent deviant speech behaviours than TD
peers, involving syllable structure changes (phoneme additions/omissions),
phoneme substitutions, fluency errors and repetitions/revisions. Participants with
SLI also had a higher incidence of neuromotor deficits. Persistent SLI appears to
relate to a multifactorial etiology, involving both genetic and early history factors.
There was high comorbidity of attention deficits, with implications for resource
allocation.
Results were interpreted within a functional capacity viewpoint. Speech
deficits are thought to contribute to a threshold effect, where even subtle deficits
in one area can compromise processing in another area. Speech production in this
population appears to be more resource-demanding than in TD peers, which may
affect concurrent performance on linguistic and memory tasks. This hypothesis is
supported by the high correlation between speech tasks and expressive syntax for
SLI participants. The high incidence of speech deficits in adolescents with SLI
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has implications for research and clinical practice with individuals of all ages with
SLI.
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