/s/ + stop clusters in the speech of ten language-delayed children

Abstract

In the acquisition of /s/ + stop clusters, before correct production, children commonly substitute one of the members for the entire cluster, the most common substitute being a stop at the appropriate point of articulation. Furthermore, there is tentative evidence that some children attempt to distinguish the stops substituting for clusters from voiced stops. The purpose of this investigation was to compare the acquisition of /s/ + stop clusters by language-delayed children to normal acquisition, first, in terms of phonemic substitutions and, second, in terms of differential use of VOT for the substituted stops. Ten children diagnosed as language-delayed served as subjects, C.A. 3;0 to 8;7; all used language below expectation for their chronological age. Each child recorded three tokens of near minimal triplets, beginning with a voiced stop, a voiceless stop and an /s/ + stop cluster, (e.g., Kate, gate, skate), for all three points of articulation, bilabial, alveolar, and velar in the course of identifying pictures. The children produced 95% of the intended clusters as singleton stops. VOT measurements for all stops were made from spectrograms. If the criterion for appropriate use of VOT to distinguish voiced from voiceless stops is taken to be +30 ms, then six of the ten children were producing voiceless and voiced stops appropriately over 80% of the time. For these children, 86% of the stops substituting for clusters were produced with VOT values in the long lag range. The other four children employed a unimodal VOT distribution for all types of stops, voiceless, voiced, and substituting for clusters. The data suggest that language delayed and normal children follow similar strategies in the acquisition of /s/ + stop clusters.