Development of perceptual sensitivity to extrinsic vowel duration in infants learning American English.

8- and 14-month-old infants' perceptual sensitivity to vowel duration conditioned by post-vocalic consonantal voicing was examined. Half the infants heard CVC stimuli with short vowels, and half heard stimuli with long vowels. In both groups, stimuli with voiced and voiceless final consonants were compared. Older infants showed significant sensitivity to mismatching vowel duration and consonant voicing in the short condition but not the long condition; younger infants were not sensitive to such mismatching in either condition. The results suggest that infants' sensitivity to extrinsic vowel duration begins to develop between 8 and 14 months.