Abstract
The effect of phonotactic probability (PP) and neighbourhood density (ND) on triggering word learning was examined in children with Language Impairment (3;04-6;09) and compared to Typically Developing children. Nonwords, varying PP and ND orthogonally, were presented in a story context and their learning tested using a referent identification task. Group comparisons with receptive vocabulary as a covariate found no group differences in overall scores or in the influence of PP or ND. Therefore, there was no evidence of atypical lexical or phonological processing. 'Convergent' PP/ND (High PP/High ND; Low PP/Low ND) was optimal for word learning in both groups. This bias interacted with vocabulary knowledge. 'Divergent' PP/ND word scores (High PP/Low ND; Low PP/High ND) were positively correlated with vocabulary so the 'divergence disadvantage' reduced as vocabulary knowledge grew; an interaction hypothesized to represent developmental changes in lexical-phonological processing linked to the emergence of phonological representations.
Highlights
Many children with Language Impairment (LI) have difficulty learning new words (Alt & Plante, ; Alt, Plante & Creusere, ; Gray, ; Gray & Brinkley, ) and these difficulties extend across childhood
Do the effects of phonotactic probability (PP) and neighbourhood density (ND) differ from those found for Typically Developing (TD) children when compared with respect to vocabulary knowledge, indicating atypicality in lexical and/or phonological processing over and above that which can be explained by lexical knowledge?
These results do not support the hypothesis that phonological processing is a core deficit in LI (Bishop, ; Bowey, ; Chiat, ; Maillart et al, ; Mainela-Arnold & Evans, ; Seiger-Gardner & Brooks, ); rather, they suggest that the delay found in phonological processing in children with LI may result from, rather than cause, the more limited lexical knowledge of children with LI, and that the cause of the deficit in word learning is yet to be established
Summary
Many children with Language Impairment (LI) have difficulty learning new words (Alt & Plante, ; Alt, Plante & Creusere, ; Gray, , , ; Gray & Brinkley, ) and these difficulties extend across childhood. Most children with LI are slow to begin the process of lexical acquisition, often presenting as ‘late talkers’ (Reilly et al, ); as primary school children they require many more exposures than Typically Developing (TD) children to learn a word (Gray, , ) and create under-specified semantic representations (McGregor, Newman, Reilly & Capone, ); and, as adolescents, their vocabulary test scores fall further and further behind their TD peers (Stothard, Snowling, Bishop, Chipchase & Kaplan, ). Poor vocabulary and word learning abilities have significant implications for children’s academic outcomes. Supporting vocabulary development in children with LI could reduce the negative sequelae in educational outcome often associated with this disorder (Snowling, Adams, Bishop & Stothard, )
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