Infant discrimination of naturalistic emotional expressions: the role of face and voice.

The ability of infants to discriminate dynamic, multimodal expressions of emotion was assessed in a series of 5 experiments. In Experiment 1, 48 infants of 4 and 5 months (total N = 96) were habituated to color/sound videotapes of 6 women speaking the same script sadly or happily. Following habituation, 2 new women were presented, each speaking once in the familiarized emotion and once in the novel emotion. Order of stimulus presentation (Sad----Happy, Happy----Sad) was counterbalanced. 5-month-olds were able to discriminate the expressions in both directions, whereas 4-month-olds could discriminate them only in the Sad----Happy direction. In Experiment 2, the ability of 5- and 7-month-olds to discriminate happy and angry expressions was examined using the Happy----Angry stimulus order alone. Only the 7-month-olds could differentiate these stimuli. In Experiment 3, it was shown that 7-month-olds could not distinguish these same Happy----Angry stimuli without vocal accompaniment. The purpose of the fourth experiment was to determine whether the voice played an equally important role in the Sad----Happy discrimination of Experiment 1. Surprisingly, a 5-month group tested without voice readily discriminated these stimuli. Finally, the fifth experiment sought to determine whether an Angry----Happy comparison might also be discriminable without voice. A 7-month group tested in this manner could not discriminate these expressions, while a group tested with voice could. The results indicate that infants can differentiate dynamic, multimodal expressions as early as 5 months, that they distinguish dynamically distinct expressions earlier than more similarly animated expressions, and that they seem to rely more on the voice than the face in making these discriminations.