On the nature of rate-dependent processing during phonetic perception.

Abstract

We previously reported (Miller& Liberman, 1979) that when listeners use transition duration to identify syllables as /ba/or /wa/, they do so in relation to the overall duration of the syllables: As the syllables become longer and are perceived as having been produced at a slower rate of speech, the transition duration that differentiates /ba/ from /wa/ also becomes longer. In the present experiments, we investigated whether the adjustment for rate was based on the actual physical rate of the syllables (i.e., syllable duration) or on their subjective rate. We used an anchoring procedure to alter the subjective rate of the syllables while keeping physical rate constant, and then assessed the effect of this manipulation on the identification of the syllables as /ba/ or /wa/.We found that changes in subjective rate induced by the anchoring procedure had no reliable effect on syllable identification. However, in a control study, changes in physical rate that produced equivalent changes in subjective rate did reliably alter identification of the syllables. These findings indicate that, during phonetic perception, listeners accommodate for changes in the physical rate of speech, not for changes in its subjective rate.