A multi-dimensional approach to gradient change in phonological acquisition: A case study of disordered speech development

The purpose of the current study is to document phonological change from a multidimensional perspective for a 3-year-old boy with phonological disorder by comparing three measures: (1) accuracy of consonant productions, (2) dynamic assessment, and (3) acoustic analysis. The methods included collecting a sample of the targets s, ∫, t∫, and d produced in single words and repeated over time. The samples were analysed using phonetic transcription and acoustic measures of duration, spectral mean, and spectral variance. A dynamic assessment was administered that showed change in response to cues and linguistic environments using a 15-point scale. The results from the three measures were compared for gradient change and evidence of covert contrasts. In conclusion, gradient change was illustrated across the three measures and contrasts were evident in the child's phonological system. Acoustic measures were most sensitive, followed by dynamic assessment; however, accuracy scores based on phonetic transcription showed little to no change for some targets.