Date of Award

1992

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Raymond G. Daniloff

Abstract

The transition portion of the speech signal has been identified as critical to the perception of both consonants and vowels. Furui (1986) demonstrated that for adult Japanese speakers a 10 ms segment of the transition centered on the area of maximum spectral movement contained the most critical information for joint consonant and vowel perception. The distribution of phonemic cues contained within consonant-vowel (CV) non-reduplicated (NRB) syllables of infants ages 6 months to 15 months was compared to the distribution observed in adult productions to examine the extent of coproductive overlap of infant consonant and vowel gestures. Truncated versions of infant CV syllables in which initial and final portions of the syllable were systematically deleted were presented to adult listeners for syllable identification. Perceptual critical points (truncation point at which syllable identification fell below 60% for the first time) were determined for both initial and final truncation conditions, and critical intervals were calculated. Results revealed significant differences in the temporal distribution and strength of phonemic cues within the infant NRB CV syllable. First, perceptual critical points could only be determined in approximately 2/3 of the 60 NRB syllables included in the perceptual study, and fewer than 1/3 of the infant syllables demonstrated normal, adult-like identification functions under both initial and final truncation conditions. Obviously, the infant syllables did not manifest the level of cue redundancy or cue constancy seen in adult syllables. Second, infant critical intervals were on the average 2 1/2 times longer than those of adult Japanese speakers reflecting an overlap of the separate consonant and vowel gestures that is less compact than in adult syllables. Results also failed to identify a clear developmental progression towards either more adult-like critical interval durations or identification functions in the NRB syllables studied.

Pages

167

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