Atypical speech production of multisyllabic items by children with developmental language disorder (DLD) indicate prosodic difficulties

Purpose: Developmental language disorder (DLD) is typically characterized by a core grammatical impairment, yet spoken word production can also exhibit atypical phonology, for example the omission of unstressed syllables. This may indicate a role for the sensory/neural processing of syllable stress patterns in the aetiology of DLD. Here we explore this connection by investigating the accuracy of the production of multisyllabic words from a speech rhythm/syllable stress perspective.Method: We adapted a computerized speech copying task originally designed for children with dyslexia, in which participants copy aloud familiar targets like “alligator”. Fifty-seven children with and without DLD were tested with a 30-item battery comprising equal numbers of 2-syllable, 3-syllable and 4-syllable words. The children with DLD (N=20) were compared with both age-matched typically-developing control children (AMC, N=21) and younger typically-developing control children with less mature language skills (younger language controls, YLC, N=16). Similarity of the child’s productions to the target in terms of the speech amplitude envelope (AE) and pitch contour was computed using two similarity metrics, correlation and mutual information. Both the speech AE and the pitch contour contain important information about stress patterns and intonational information.Results: Children with DLD were significantly less accurate than AMC at copying the multi-syllabic targets, for both the AE and the pitch contour. The opportunity to repeat the targets had no impact on performance, for any group. Word length effects were similar across groups. Conclusion: The spoken production of multisyllabic words by children with DLD is atypical regarding both the AE and the pitch contour. This is consistent with a theoretical explanation of DLD based on impaired sensory/neural processing of speech rhythm.