Infants use onset asynchrony cues in auditory scene analysis.

This experiment investigated the effect of onset asynchrony on the segregation of concurrent vowels in infants and adults. Two vowels, randomly chosen from seven American-English vowels, were superimposed. Each vowel pair contained one vowel by a male and one by a female talker. A train of such vowel pairs was presented to listeners, who were trained to respond to the male target vowel /i:/ or /u:/. The ability to identify the target vowel was compared among three conditions: synchronous onset, 100-, and 200-ms onset asynchrony. Experiment 1 measured performance, in d', in 7-month-old infants and adults. Infants and adults performed better with asynchronous than synchronous vowel onset, regardless of asynchrony duration. Experiment 2 compared the proportion of 3-month-old infants achieving an 80% correct criterion with and without onset asynchrony. Significantly more infants reached criterion with asynchronous than with synchronous vowel onset. Asynchrony duration did not influence performance. These experiments show that infants, as young as 3 months old, benefit from onset asynchrony.