Differentiating the effects of phonotactic probability and neighborhood density on vocabulary comprehension and production: A comparison of preschool children with versus without phonological delays

Abstract

This is the author's accepted manuscript. The original publication is available at http://jslhr.pubs.asha.org/article.aspx?articleid=1781591Purpose The purpose of this study was to differentiate the effect of phonotactic probability from that of neighborhood density on a vocabulary probe administered to preschool children with or without a phonological delay. Method Twenty preschool children with functional phonological delays and 34 preschool children with typical language development completed a 121 item vocabulary probe in both an expressive and receptive response format. Words on the vocabulary probe orthogonally varied on phonotactic probability and neighborhood density but were matched on age-of-acquisition, word frequency, word length, semantic set size, concreteness, familiarity, and imagability. Results Results showed an interaction between phonotactic probability and neighborhood density with variation across groups. Specifically, the optimal conditions for typically developing children were rare phonotactic probability with sparse neighborhoods and common phonotactic probability with dense neighborhoods. In contrast, only rare phonotactic probability with sparse neighborhoods was optimal for children with phonological delays. Conclusions Rare sound sequences and sparse neighborhoods may facilitate triggering of word learning for typically developing children and children with phonological delays. In contrast, common sound sequences and dense neighborhoods may facilitate configuration and engagement for typically developing children but not children with phonological delays due to their weaker phonological and/or lexical representations