Factors Underlying Tongue Articulation in Speech

A factor analysis of 11 measures of lingual activity involved in the production of the syllable /ka/ showed that three factors can explain about 75% of the variance in the data. Measures of displacement and velocity loaded strongly on the first factor, durational measures loaded strongly on the second factor, and midsyllable durational and distance measures loaded on the third factor. This three-factor solution emerged from each of four conditions involving manipulations of speed of delivery and linguistic context. Canonical correlations showed that the best of four linear additive models involving 3 of the 11 variables was able to explain 45% of the variance in the remaining 8 variables. The three best predictor variables were (a) descending movement displacement, (b) linguo laryngeal movement onset delay, and (c) time to peak velocity for the ascending movement. It is argued that these variables represent the speech system's control over the articulatory distinction of different sounds, interarticulatory coordination, and, perhaps, rhythm adjustment, and that the first two factors correspond to central variables of breakdown in Broca's aphasia.