Infants' vocalized emotions : listener identification and acoustical analysis

Six infants were video recorded during 5 emotional conditions (anger, fear, separation, joy, and elation). The 30 randomized samples were only presented auditorily to a group of 20 listeners (mothers), who identified which of the five emotions they perceived. A significant difference in the auditory identification by the listeners was observed among the 5 emotions. The listeners perceived the positive emotions as the targeted emotion at a higher percent than the negative emotions. Intrajudge, interjudge and test-retest reliabilities were higher for negative/positive identification of the emotions than for specific emotions. A significant difference among the 6 infants indicated that the vocalized emotions of the group were not homogeneous. Infant 3 (13 months of age) had the highest percent of responses which were the same as the targeted emotions; whereas. Infant 1 (9 months of age) had the lowest percent of responses. All five sampled emotions for Infant 3 met the 70% criterion (14 out of 20 listeners); whereas Infant 1 had only 1 of 5 emotions that satisfied the criterion. These 70% criterion samples were used for the acoustical analysis. Six acoustic parameters were measured for 43% of the samples (13 out of 30). These were mean fundamental frequency (Fo), mean Fo range, mean Fo inflection, mean Fo rate, mean relative amplitude range, and mean relative amplitude rate. The positive emotions had the highest values for all the acoustic parameters, except for mean Fo which was highest for anger. This emotional/acoustic relationship suggested a continuum ranging from the most negative to the most positive emotion with increasing values in all acoustic parameters except mean Fo. A comparison of the perception of infants' emotions with adults' emotions revealed that adult emotions are easier to perceive than infant emotions. The mean fundamental frequency (Fo) inflection and Fo rate of the adults' emotions were higher than those of infants'. Mean Fo rate was similar in the ranking of the three emotions for both the adults and the infants. Emotions have discriminating acoustical characteristics for both infants and adults.