Risk Factors for Language Problems

Along with typical development, work in the Speech Development Laboratory has examined the perceptual underpinnings of language-learning problems.  The principal motivation for this work is to improve our understanding of the language-learning problems faced by children with hearing loss.  However, studies with other populations of children extend our understanding of the effects of hearing loss on language learning and, at the same time, provide insights into the problems faced by those populations.

The hypothesis underlying this work is that early language experience shapes perceptual weighting strategies for speech, and so affects the child’s ability to recover segmental structure from the acoustic speech signal.  To test this hypothesis, children presumably varying in the amount and kind of early language experience have participated in studies of speech perception, phonological processing and awareness, and syntactic comprehension.  Specifically, the three populations sampled have been: children with early, chronic histories of otitis media with effusion, children living in conditions of low socio-economic status, and children with permanent hearing loss.

For example, language users who readily recover segmental structure show better recall of linguistic material than those who do not.  The reason behind this phenomenon is that processing strategies using phonological codes to store words in working memory provide advantages over strategies that do not.  This can be demonstrated by the finding that adults with normal language abilities more accurately recall lists of nonrhyming words than lists of rhyming words:

[rhyming words]                 [nonrhyming words]

The reason is simply that nonrhyming words are more dissimilar phonologically, and so a phonological code enhances recall.
So far, data collected have supported the hypothesis: For the most part, children in all three groups have demonstrated similar deficits in speech perception, phonological processing and awareness, and syntactic comprehension.  The one exception has been that children with hearing loss who received intensive early intervention were functioning as their normal-hearing peers.

One suggestion that has not received support is that of advocates for intervention strategies that focus on nonspeech, auditory practice for children with language-learning problems, such as FastForward.  The rationale underlying that approach is that these children have deficits processing temporal information in the acoustic speech signal.  To test this hypothesis, children’s accuracy on temporal order judgments was evaluated: Children were asked to replicate sequences of tones presented with varying interstimulus intervals.  The [easiest condition] had two tones with interstimulus intervals of 320 ms.  The [hardest condition] had four tones with interstimulus intervals of 20 ms.  No differences in performance were found between children with normal and delayed language development.