Talkers alter vowel production in response to real-time formant perturbation even when instructed not to compensate

Talkers show sensitivity to a range of perturbations of auditory feedback (e.g., manipulation of vocal amplitude, fundamental frequency and formant frequency). Here, 50 subjects spoke a monosyllable ("head"), and the formants in their speech were shifted in real time using a custom signal processing system that provided feedback over headphones.

First and second formants were altered so that the auditory feedback matched subjects' production of "had." Three different instructions were tested: (1) control, in which subjects were naive about the feedback manipulation, (2) ignore headphones, in which subjects were told that their voice might sound different and to ignore what they heard in the headphones, and (3) avoid compensation, in which subjects were informed in detail about the manipulation and were told not to compensate.

Despite explicit instruction to ignore the feedback changes, subjects produced a robust compensation in all conditions. There were no differences in the magnitudes of the first or second formant changes between groups. In general, subjects altered their vowel formant values in a direction opposite to the perturbation, as if to cancel its effects.

These results suggest that compensation in the face of formant perturbation is relatively automatic, and the response is not easily modified by conscious strategy.