Developmental phonological disorders. III: Long-term speech-sound normalization.

Prior articles in this series provide a descriptive profile of 178 children with developmental phonological disorders (Shriberg & Kwiatkowski, 1994) and predictive correlates of short-term speech-sound normalization in 54 children (Shriberg, Kwiatkowski, & Gruber, 1994). The present article reports findings from a study of 10 children with developmental phonological disorders whose progress was followed at least once yearly for 7 years. Analyses characterize the sequence, rates, and error patterns of long-term speech-sound normalization in relation to developmental perspectives on the nature of children's phonological disorders. Findings are interpreted to support the hypothesis of a critical period for speech-sound development, with long-term normalization of significant speech delay reaching a chronological age boundary at approximately 8.5 years.