The perceptual consequences of overlap in /s/ and /∫/ productions within a talker

Abstract

A primary issue in speech perception is the apparent lack of invariance between the acoustic information in a signal and the listeners perception. Different intended phonemes may be produced with identical acoustic values. Previously, we examined fricative centroids and frication peaks for over 100 utterances beginning with /s/ and /∫/ from each of 20 different speakers, and found substantial overlap across talkers. In the present study, we examine the effect of this overlap on perception. Listeners in a phoneme identification task heard natural productions of /s/ and /∫/ syllables from speakers with either little or great overlap between categories. Although labeling accuracy was near ceiling, effects were found in listeners’ reaction times. Listeners needed more time to interpret the speech of talkers who had substantial overlap in their fricative centroids, even when these talkers showed no overlap in their frication peaks. Listeners also had slower reaction times for talkers with overlap in their frication peaks, but not their centroids. This suggests that category overlap has measureable consequences to perception, and that peaks and centroids are sensitive to different aspects of the speech signal, both of which are perceptually impotant to listeners. [Work supported by NIDCD Grant R01-DC00219 to SUNY at Buffalo.]