The perception of others' emotions should be one of the most important aspects to form our communication, especially when considering communicative function of emotional expression of humans as well as nonhuman animals. We would say that the perception of emotion entails understanding how another person feels internally by attending to his or her external expressions, words, and other actions. Developmental studies in these 20-30 years have shown that human infants can discriminate different facial expressions from quite early stage of their life, at least from 4 month old. However, though understanding of others' emotions does include being able to discriminate among and within examples of emotional expression, it is still unclear what behavior does the infant take in response to the expressed emotions.
Adult individuals react differently to others' expressed emotions. Would the young infants also respond fearfully to anger faces, with smiles to happy faces, and so forth? We experimentally examined the infants' response to expressed emotions shown in the video monitor. The subjects were ten 4-5 months old infants (5 females and 5 males) and ten 6-7 month old infants (5 females and 5 males). Infants were shown video events in which an adult female facially expresses one of three categories of emotion, smile, anger, and neutral (counting numbers without overt facial expression). Three adult females, unfamiliar for the infants, were asked to express these emotions (three different stimuli per one category of expression were prepared). The video images of the actress taken from the front were edited to 20 seconds each and were used as stimuli. Half of the subjects were shown the stimulus with corresponding voice and the other half were shown it without voice. In one session was the infant shown 6 to 8 events. All of the stimulus categories appeared within one session and the order of the presentation was quasi randomized. The analysis of looking time showed no significant difference between categories of expressed emotion or with / without voice conditions, regardless of the infants' age. The analysis of duration of smiling response showed no significant difference between conditions described above in 4-5 month old infants. However, in 6-7 months olds, infants smiled for longer duration at the video images in which the actress expressed smile. Differential expression of smiling to the other's facial expressions was not observed in 4-5 month olds, but emerged 6-7 month olds. Spitz and Wolf (1946) displayed various facial expressions to young infants ranged from 3 to 6 months old and reported that subjects were more apt to laugh out loud, even to the fearfully anger expressions. The present results partly support their findings and suggest importance of further studies to figure out the mechanism for infants to acquire smiling response in communicative context.

HASHIYA, Kazuhide
Department of Cognitive Psychology,
School of Education, Kyoto University
Yoshida Honmachi, Sakyo-Ku, Kyoto
606-8501, Japan
hashiya@mindless.com