Different Origin of Auditory and Phonological Processing Problems in Children With Language Impairment

Abstract

This study investigated the heritability of auditory processing impairment, as assessed by Tallal's Auditory Repetition Test (ART). The sample consisted of 37 same-sex twin pairs who had previously been selected because one or both twins met criteria for language impairment (LI) and 104 same-sex twin pairs in the same age range (7 to 13 years) from the general population. These samples yielded 55 children who met criteria for LI, who were compared with 76 children whose language was normal for their age (LN group). We replicated earlier work showing that group LI is impaired relative to group LN on ART. However, there was no evidence of a heritable influence on ART scores: Correlations between twins and their co-twins were reasonably high for both MZ and DZ twins, suggesting that performance is more influenced by shared environment than genetic factors. Analyses of extreme scores gave a similar picture of nonsignificant group heritability. In contrast, a test of phonological short-term memory, the Children's Nonword Repetition Test (CNRep), gave high estimates of group heritability. In general, CNRep was a better predictor of low language test scores than ART, but ART did make a significant independent contribution in accounting for variance in a test of grammatical understanding.

Language in autism and specific language impairment: Where are the links?

“…In each analysis, though, non-word repetition performance was the only factor that was needed to discriminate one group of parents from the other, yielding a specificity of approximately 78% and a sensitivity of approximately 70%. These findings, along with those of Bishop et al (1996Bishop et al ( , 1999, provide strong evidence for the familial aggregation of phonological processing difficulties in language impairment of kinds generally recognised as characteristic of SLI.…”

“…The Arithmetic, Digit Span, and Information subtests do not assess higher-order language processing directly, although they have a verbal loading. VIQ also appears insensitive to phonological and grammatical impairments as evident from the fact that individuals with a history of SLI show deficits in these aspects of language, particularly phonology, even when VIQ is relatively unimpaired (Bishop et al, 1996;Bishop et al, 1999;Lewis & Freebairn, 1992;Tomblin, Freese & Records, 1992).…”

Developmental dyslexia: specific phonological deficit or general sensorimotor dysfunction?

“…In fact, there is good evidence that it is an optional feature of a number of developmental disorders, including SLI, autism, dyspraxia, and Williams syndrome [71][72][73][74][75]. The optional character of the sensorimotor syndrome also makes sense in the light of genetic studies showing that the phonological deficit is highly heritable, whereas auditory and visual disorders are not [56, 76,77].…”

From temporal processing to developmental language disorders: mind the gap

“…On the one hand, behavioural genetics has consistently come up with heritability estimates exceeding 0.50, increasing with age, and occasionally approaching dizzying values around 0.80 for literacy skills such as fluency, decoding, spelling and comprehension, and for the diagnosis of reading or other disabilities [128][129][130][131][132][133] (but no comparable heritability for performance on the repetition test [134]). On the other hand, molecular genetics have failed to identify individual genes as singularly culpable for a diagnosis of dyslexia [112,126,127,135,136].…”