Temporal analysis of articulatory speech errors using direct image analysis of real time magnetic resonance imaging.

Abstract

Articulometry studies have demonstrated that speech errors often involve gestural intrusions that are coproduced with other gestures and can go unnoticed because they are not always perceived to be segmental errors. [Mowrey and MacKay (1990)]. Real time magnetic resonance imaging was used to examine tongue movement during the production of English minimal pairs “cop-top,” “kid-kim,” “sop-shop,” and “bad-bang.” Subjects’ upper airways were imaged in the midsagittal plane while they uttered repetitions of each word pair as rapidly as possible for 15 sec. Degree of constriction in each region of interest (labial, alveolar, post-alveolar, and velic) was automatically tracked with direct image processing techniques. We calculate the mean intensity of temporally correlated pixels in that region–a metric which has been found to provide a robust estimate of constriction degree in noisy data. [Lammert (in preparation).] Gestural intrusions are observed throughout these data; frequency of occurrence increases with speech rate. Intrusions are invariably synchronous with the alternating contrastive gesture, e.g., additional velic gestures are observed at the same time as the tongue tip constriction in the word pair “cop-top.” These data are consistent with the hypothesis that speech production involves the coordination of dynamically defined action units. [Goldstein et al. (2007).]