Four Cases of Children With Phonological Impairment and Precocious Vocabulary: making sense of a clinical conundrum

Purpose: The purpose of this study was to describe the speech production, speech perception, vocabulary, and word learning abilities of lexically precocious 4-year-old children with phonological impairment, in an effort to better understand the underlying nature of phonological impairment in children. Method: Using a case series approach, we identified four children with phonological impairment and precocious vocabulary abilities. Each child completed routine speech production and vocabulary assessments, as well as experimental speech perception and word learning tasks. The results from these tasks were then used to create profiles of each child's individual strengths and needs across the abilities assessed. Results: Although all four children presented with phonological impairment and lexically precocious receptive and expressive vocabulary, they differed in their specific speech errors. One child presented with phonological speech errors only, while the other three children presented with an interdental lisp alongside their phonological errors. Three children presented with average speech perception abilities, and one child presented with poorer speech perception. The same three children also showed some learning of novel nonwords 1 week post-initial exposure, while the other child showed no evidence of word learning 1 week post-initial exposure. Conclusions: The clinical profiles of lexically precocious children with phonological impairment offered different insights into the nature of the problem. Although one child appeared to present with underspecified underlying representations of words, the other three children appeared to present with wellspecified underlying representations. Of the three children with well-specified underlying representations, two appeared to have difficulty abstracting particular rules of the ambient phonological system. Further research is needed to improve our understanding of the underlying nature of phonological impairment.