Visual recognition of mother by young infants: facilitation by speech.

Infants recognise their mother's voice at birth but appear not to recognise visual-only presentations of her face until around 3 months. In a series of experiments visual discrimination by infants aged 1, 3, and 5 months of their mother's and a female stranger's face was investigated in visual-only and visual-plus-speech conditions. In the first experiment these infants' discrimination of mother's and female stranger's faces was measured by their visual-fixation-preference scores. Discrimination was found to be facilitated by the addition of speech information. In experiment 2 naive adults viewed silent videotapes of infants from experiment 1 and judged whether the mother had been presented on the infants' left or right. This added further information to the fixation-preference results of experiment 1: it was found that 1-month-olds discriminate mother's and stranger's face only in the presence of speech information, whereas 3-month-olds also do so in visual-only conditions. In experiments 3 and 4 the relative salience of lip movements and voice information in visual recognition of mother's face was investigated. In experiment 3, no significant differences in infants' visual-fixation-preference scores were obtained. However, in experiment 4 adults' 'where is mother?' judgments of video-tapes from experiment 3 were found to be more accurate in the voice than in the lip-movements conditions, especially for the 3-month-olds and more accurate when mother rather than stranger was talking. It is concluded that young infants' visual recognition of mother is facilitated by addition of speech information, that it is primarily the voice component of speech that causes this facilitation, and that social discrimination is best indexed by a dependent variable which is sensitive to a range of facial cues provided by infants.