Tuesday, June 28, 2016

The sensitivity of children with SLI to phonotactic probabilities during lexical access.

Quemart, P. & Maillart, C. (2016). The sensitivity of children with SLI to phonotactic probabilities during lexical access. Journal of Communication Disorders, 61, 48-59.

This study examined how children with specific language impairment (SLI) use certain language cues to help with vocabulary learning. Children with SLI have typical intelligence, hearing, and motor skills, but struggle with learning language at the same rate as their peers. Examining different factors that lead to successful vocabulary acquisition may contribute to our understanding of the language difficulties seen in children with SLI. Sensitivity to phonotactic constraints may be one factor that helps language learners with vocabulary acquisition. Phonotactic constraints are how sounds can be ordered within words within a particular language. For instance, English words can end with /fs/ (e.g., ‘laughs’), but cannot begin with /fs/. Phontactic constraints vary within a language, with some constraints occurring across more words, or being more frequent, than others. These constraints are easily acquired: By about nine months of age, infants are able to differentiate between legal and non-legal phonotactic constraints in their native language. Once acquired, knowledge of phonotactic constraints is involved in word learning, spoken word recognition, and the selection of appropriate verb inflections. The authors wanted to examine whether children with SLI were sensitive to phonotactic constraints, and whether this sensitivity differed from that of typically developing children.

Children with SLI and typically developing children heard a list of words and non-words, one at a time, and had to correctly identify the real words and correctly reject the nonwords. Importantly, the nonwords were made up of phonotactic constraints that were highly frequent in their native language (French), or phonotactic constraints that were not frequent. That is, some of the nonwords were made up of sound combinations that occur in many French words, while others were made up of sound combinations that occur in few French words. If the children were sensitive to patterns involving phonotactic constraints, it should be easier to quickly reject the nonwords containing non-frequent sound combinations, and harder to reject the nonwords containing highly frequent sound combinations. The authors found that compared to typically developing children, children with SLI were worse at correctly rejecting nonwords that contained highly frequent phonotactic constraints. That is, the children with SLI had more difficulty rejecting nonwords that sounded similar to other words in their vocabulary. Typically developing children, on the other hand, could quickly and accurately reject all of the nonwords, perhaps because they had a better-developed vocabulary.

It seems that children with SLI are at least sensitive to the phonotactic constraints within their native language. But, they may be over-reliant on this cue compared to children with typical language skills, who can instead rely on their stronger vocabulary knowledge. These results underscore the importance of vocabulary knowledge in supporting language processing, and the need to support vocabulary learning in children with SLI perhaps on an extended basis.

Blogger: Nicolette Noonan is a Ph.D. student with Drs. Lisa Archibald and Marc Joanisse

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