Matching phonetic information in lips and voice is robust in 4.5-month-old infants

Past research (Kuhl & Meltzoff, 1982, 1984) shows that 4.5-month-old infants can match phonetic information in the lips and voice. These studies used female faces surrounded by black cloth to occlude possible distractions. The present studies were conducted to replicate and extend past research by examining how robust the ability to match phonetic information in lips and voice is at 4.5-months of age. If speech is represented intermodally in young infants then they should show evidence of matching phonetic information when presented with faces shown from the shoulders up, revealing hair and some clothing, and with male as well as female models. In each of two studies, 32 infants were seated in front of two side-by-side video monitors displaying filmed images of a female face (Study 1) or a male face (Study 2). The face on each side articulated a different vowel sound (/i/ or /a/) in synchrony. The sound track was played through a central speaker and corresponded to one of the two vowels but was synchronous with both. Infants spent approximately equal amounts of time looking and smiling at both the female and the male faces (p > .05). However, infants looked longer at the face that matched the heard vowel for both female and male stimuli (p < .01). Also, infants showed articulatory imitation in response to the matching face/voice stimuli (p < .05). The finding that bimodal phonetic matching is replicated with full, naturalistic heads and with male stimuli supports the hypothesis that infants are able to link phonetic information presented in the lips and voice. This supports an integrated, multi-modal representation of articulatory and acoustic phonetic information at 4.5-months of age.