The influence of auditory acuity on acoustic variability and the use of motor equivalence during adaptation to a perturbation

PURPOSE: The aim of this study was to relate speakers' auditory acuity for the sibilant contrast, their use of motor equivalent trading relationships in producing the sibilant /∫/, and their produced acoustic distance between the sibilants /s/ and /∫/. Specifically, the study tested the hypotheses that during adaptation to a perturbation of vocal-tract shape, high-acuity speakers use motor equivalence strategies to a greater extent than do low-acuity speakers in order to reach their smaller phonemic goal regions, and that high-acuity speakers produce greater acoustic distance between 2 sibilant phonemes than do low-acuity speakers. METHOD: Articulographic data from 7 German speakers adapting to a perturbation were analyzed for the use of motor equivalence. The speakers' produced acoustic distance between /s/ and /∫/ was calculated. Auditory acuity was assessed for the same speakers. RESULTS: High-acuity speakers used motor equivalence to a greater extent when adapting to a perturbation than did low-acuity speakers. Additionally, high-acuity speakers produced greater acoustic contrasts than did low-acuity-speakers. It was observed that speech rate had an influence on the use of motor equivalence: Slow speakers used motor equivalence to a lesser degree than did fast speakers. CONCLUSION: These results provide support for the mutual interdependence of speech perception and production.