Compensatory Responses to Formant Perturbations Proportionally Decrease as Perturbations Increase.

Purpose We continuously monitor our speech output to detect potential errors in our productions. When we encounter errors, we rapidly change our speech output to compensate for the errors. However, it remains unclear whether we adjust the magnitude of our compensatory responses based on the characteristics of errors. Method Participants (N = 30 adults) produced monosyllabic words containing /ɛ/ (/hɛp/, /hɛd/, /hɛk/) while receiving perturbed or unperturbed auditory feedback. In the perturbed trials, we applied two different types of formant perturbations: (a) the F1 shift, in which the first formant of /ɛ/ was increased, and (b) the F1-F2 shift, in which the first formant was increased and the second formant was decreased to make a participant's /ɛ/ sound like his or her /æ/. In each perturbation condition, we applied three participant-specific perturbation magnitudes (0.5, 1.0, and 1.5 ɛ-æ distance). Results Compensatory responses to perturbations with the magnitude of 1.5 ɛ-æ were proportionally smaller than responses to perturbation magnitudes of 0.5 ɛ-æ. Responses to the F1-F2 shift were larger than responses to the F1 shift regardless of the perturbation magnitude. Additionally, compensatory responses for /hɛd/ were smaller than responses for /hɛp/ and /hɛk/. Conclusions Overall, these results suggest that the brain uses its error evaluation to determine the extent of compensatory responses. The brain may also consider categorical errors and phonemic environments (e.g., articulatory configurations of the following phoneme) to determine the magnitude of its compensatory responses to auditory errors.