This study investigated the response behavior of nine infants, aged 13-15 weeks, to a recurrent pattern of visual and verbal stimuli presented by their own mothers and by female strangers. The infants were presented with the following 2-minute sequence (repeated 3 times): (1) one-half minute of an unknown female leaning over the crib with a nonresponsive face, nodding her head and counting, (2) one-half minute of silence, (3) one-half minute of the mother engaged in the same behavior as the unknown female, and (4) one-half minute of silence. The infant behaviors observed were: (1) smiling, (2) head turning, (3) activity level, and (4) vocalizations (i.e., cooing, laughter or gurgle, fussing, crying, or visceral noise). Results showed that infants were more responsive (i.e., smile more, turned the head more, cooed more, and were more active) to female strangers than to their mothers. Cooing to the female stranger was related to ratings of maternal warmth and maternal vocalization to infants during the first three months of life. (Author/BRT)