Perceptual evaluation of infant articulatory transitions

The distribution of phonemic cues contained within consonant–vowel (CV) nonreduplicated (NRB) syllables of infants ages 6 to 15 months was compared to the distribution observed in adult productions [S. Furui, J. Acoust. Soc. Am. 57, 1016–1025 (1986)] to examine the extent of coproductive overlap of infant consonant and vowel gestures. Truncated versions of infant CV syllables 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. Fewer than 1/3 of the infant syllables demonstrated normal, adult-like identification functions under both initial and final truncation conditions, and infant critical intervals were on the average 21/2 times longer than those of adult Japanese speakers. Results did not reveal a clear developmental progression towards either more adult-like critical interval durations or identification functions in the NRB syllables studied.