Speech perception by the chinchilla: Categorical perception of synthetic alveolar plosive consonants

Abstract

Kuhl and Miller [Science 190, 69–72 (1975)] recently demonstrated that in an identification task the chinchilla responds to (“labels”) an alveolar synthetic-speech continuum as though an abrupt qualitative change occurs at the place where English speakers hear a change from /da/ to /ta/. Discrimination functions for these same stimuli have now been obtained. The animal's task is to detect a change from a repeating “standard” stimulus to a “comparison” stimulus and report that change by crossing a midline barrier to avoid shock. The standard stimuli are 0, +10, +20, +30, +40, +50, +60, +70 and +80 msec VOT. The VOT value of the comparison stimulus is gradually changed until it approaches the VOT value of the standard. The animal's threshold (the minimum Δt detected with 75% accuracy) is measured for each standard stimulus and is best when the standard is +30 msec VOT, that is, at the animal's perceptual boundary as defined in the labeling experiments. This agreement between the labeling and discrimination data demonstrates categorical perception for a voiced-voiceless continuum by an animal listener. [Supported by NIH grant NS 03856 to CID.]