Psychophysical detection threshold of formant manipulations during speech production

Abstract

In altered auditory feedback experiments, participants respond rapidly and alter their speech production to compensate for the induced auditory feedback error. This response does not occur with small feedback perturbations, and thus there must be a threshold for compensation by the auditory‐vocal feedback system. What is unknown is the psychophysical threshold during speech production (i.e., how large are manipulations that are consciously detectable?). The purpose of this experiment was to compare the threshold for conscious awareness of perturbation, and the minimal change that induces compensation. A real‐time auditory feedback manipulation system was employed in a repeated measures design. The compensation threshold was determined using the change point test during a perturbation ramp of 4 Hz/utterance. In the psychophysical measurement, the size of the feedback manipulation followed a two‐alternative forced‐choice paradigm. With 17 individuals, the mean psychophysical threshold was 105 Hz (SE: 9 Hz). The mean compensation threshold was 64 Hz (SE: 8 Hz). The significant difference between these thresholds is consistent with the hypothesis that the auditory‐vocal feedback system can operate without conscious control and suggests that it may have access to a more sensitive representation of speech formants.