Trading relations in speech and nonspeech

Abstract

Two acoustic variables that correlate with the distinction between intervocalic [b] and [p] are closure duration and presence or absence of low-frequency glottal pulsing during the closure interval. These variables may be considered to exhibit a trading relation (Repp, 1982), to the extent that a longer closure is required to perceive the consonant as voiceless when glottal pulsing is present than when it is not. Such trading relations have been interpreted as reflecting a special speech mode of perception. In the present experiments, we demonstrated a trading relation between closure duration and closure pulsing for a set of [aba]-[apa] stimuli. Next we showed that a similar effect could be obtained with square-wave analogue stimuli that mimicked the segment durations and peak amplitudes of the speech stimuli but that were not phonetically categorizable. This nonspeech trading relation depended on the degree of spectral continuity between the low-frequency pulsing and the adjacent portions of the square wave. The implications of these results for the speech mode hypothesis are discussed. © 1986 Psychonomic Society, Inc.