Identifying possible underlying mechanisms of developmental speech sound disorders with the Nonword Repetition Task
Purpose: The Nonword Repetition Task (NRT) was used as a tool to examine possible underlying mechanisms of developmental speech sound disorders (SSD). Specifically, deficits related to phonological encoding were examined. Method: Twenty-four children with SSD (3-7 years) and 24 typically developing (TD) children were administered the NRT. Four accuracy measures were calculated: percent consonants correct (PCC), consonant place of articulation, consonant manner of articulation, and consonant voicing. In addition, the verbal response time to produce each nonword was measured.Results: Children with SSD were less accurate in their repetition of nonwords than TD children, even after their speech sound production ability was taken into account, suggesting that a deficit beyond articulation was affecting their performance. Children with SSD demonstrated phonological encoding difficulties, as their ability to accurately represent the phonetic articulation characteristics of consonants was impaired. Moreover, children with SSD demonstrated much faster verbal response times than their TD peers; more accurate NRT responses were correlated with slower verbal response times.Conclusion: These results suggest that children with SSD may have phonological encoding deficits, which might negatively impact their ability to accurately produce speech sounds. The NRT could be used to help identify underlying mechanisms of SSD, such a deficit in phonological encoding, which could lead to more effective treatment approaches.