Speech perception in early infancy: perceptual constancy for the vowel categories /a/ and /⊃/

Abstract

Six-month-old infants demonstrate perceptual constancy for the vowel categories /a/ and /l/ when both the critical (formant frequencies) and noncritical (fundamental frequency, pitch contour) acoustic dimensions are randomly varied (Kuhl, 92nd ASA Meeting). This report extends these findings to vowel categories that are spectrally and perceptually more similar. /a/ and /⊃/. Infants were tested in a task in which a head-turn response was reinforced with a visual stimulus in the presence of a phonetic token from one-vowel category but not in the presence of a phonetic token from the second-vowel category. Infants were trained on a single /a/ and a single /⊃/ token synthesized to simulate a male talker with a rise—fall pitch contour. The stimulus ensemble was then systematically increased until the tokens produced by a male, female, and child talker, each with two pitch contours (rise and rise—fall), were included in each vowel category. The data show that the /a/ and /⊃/ categories are readily differentiated by the six month old in this perceptual constancy paradigm. [Research supported by NICHD.]