Echoic storage in infant perception.

Preperceptual auditory of "echoic" storage was investigated in 8-9 week-old infants using a modification of an adult masking paradigm and a nonnutritive sucking discrimination procedure. Experiment 1 provided validation of a new version of the nonnutritive sucking procedure using the standard stimulus contrast [ba] versus [pa]. In experiment 2, infants were presented with repeating pairs of brief vowels with a stimulus onset asynchrony (SOA) of 50 msec for each pair. Within each series, the first vowel in a pair changed (backward masking), the second vowel changed (forward masking), or neither vowel changed (control). Discrimination of the changed occurred in the forward- but not in the backward-masking condition. In experiment 3, discrimination occurred in a backward-masking condition with an SOA of 400 msec, but not with an SOA of 250 msec or in a control condition. In conjunction with the adult literature, these results suggest that echoic storage contributes to auditory perception in infancy, as in adulthood, but that the useful lifetime of an echoic trace may be longer in infancy.