Infants' response to the audible and visible properties of the human face: II. Discrimination of differences between singing and adult-directed speech

Human infants' responsiveness to the audible and visible features of human faces was studied by habituating them to a person speaking a prepared script in an adult-directed manner and then administering a series of separate test trials where a person could be seen, heard, or seen and heard singing. When habituated to a female person speaking in an adult-directed manner and tested with a singing female 4, 6, and 8-month-old infants responded to the audible, visible, and bimodal changes, whereas 3-month-old infants only responded to the visual and bimodal changes. In contrast, when habituated to a male person speaking in an adult-directed manner and tested with a singing female, all age groups discriminated all three types of changes. These findings demonstrate that infants are responsive to differences between low- and high-prosody content inherent in both the facial and vocal characteristics of the human face and that, whereas responsiveness to the visible and bimodal features associated with differences between adult-directed speech and singing is present as early as 3 months of age, responsiveness to the audible features emerges between 3 and 4 months of age depending on whether gender differences are present as well.