Neural Correlates of Processing Syntax in Music and ... - PubMan

Specific Language Impairment 74
independent of other systems is questioned by some evidence portraying the interactive
nature of specific systems especially when they develop. Thomas and Karmiloff-Smith
(2002) proposed the concept of interactive development, and challenged the assumption
of “residual normality” in developmental disorders. Botting (2005) provided evidence
for an interaction of non-verbal cognitive abilities that “challenge the implicit assumption
that Residual Normality is a feature of SLI, i.e., only linguistic difficulties are problematic
whilst other areas of development are ‘spared’” (p. 323). It seems unlikely that
severe deficits in general cognitive mechanisms would leave other cognitive domains
untouched. Thus, it might be appropriate to drop the term “specific” from specific language
impairment (Ors, 2002).
Nowadays, there are widely accepted diagnostic criteria for SLI (cf. Leonard, 1998).
Most of these criteria are exclusory to allow to differentiate SLI from other types of
impairment and typical, but delayed language development: [1] Linguistic abilities,
measured with a language development tests (e.g., the SETK 3-5; Grimm, Aktas, &
Frevert, 2001), must be at least 1.5 standard deviations (SD) below the mean of the
“typical” (unimpaired) population (some authors favour a less, others a more conservative
criterion [1.25 SD up to 2.00 SD]). [2] These children must have a nonverbal intelligence
with the normal range (within 2 SDs around the population mean, i.e. at least 70
IQ points) and their nonverbal IQ values must be more than 1 SD higher than their
scores in any subtest of the language development test. [3] Exclusory criteria are any
hearing difficulties or recent episodes of otitis media with effusion; anomalies with
regard to oral structure and oral motor function; or evidence of neurological dysfunctions
(as seizure, cerebral palsy or brain lesions). [4] Finally, the children must not show
any symptoms of impaired physical and social interactions (as, e.g., autistic children).
There is some discussion regarding criterion [2] (Bishop, 1997; Fey, Long, & Cleve,
1994; Lahey, 1990; Tomblin, Records et al., 1997). Some authors argue for a more
conservative criterion of at least 85 IQ points. It is acknowledged that children with SLI
show depressed general cognitive levels compared to children with TLD (Farrell &
Phelps, 2000). Further, there is evidence of interactions between language development
and non-verbal intelligence (discussed below; also see Botting, 2005). It seems highly
unlikely that such severe language deficiencies (as these of children with SLI) will go
along with IQ values in the normal range (Dannenbauer, 2004; Fey et al., 1994; Leonard,
1998). Even though a lowered IQ can be assumed as risk-factor, it surely does not
provide an exclusive explanation why children develop SLI: Some children with a below-average
non-verbal IQ will show typical language development. Moreover, it is