Rose F. Caron

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.

Abstraction of Invariant Face Expressions in Infancy.

To determine whether infants can abstract invariant face expressions across different persons (i.e., can form face expression categories), groups of 18-, 24-, and 30-week-old infants (18 boys and 18 girls per group) were habituated by the infant control procedure to photographs of 4 different female faces all wearing an identical expression (happy or surprise). In an immediately following test phase, categorization was inferred from greater generalization of habituation (less recovery of fixation) to 2 new female faces in the familiarized expression than to the same new faces in the altered (novel) expression. To rule out the possibility that generalization at test might be due to failure to discriminate the new persons, control groups of 18 boys and 18 girls at each age saw the same test faces following repeated presentations of only 1 of the 4 habituation faces. The results indicated that not until 30 weeks could infants differentiate happy and surprise expressions on a categorical basis. At 24 weeks they could distinguish a surprise expression following habituation to happy faces, but could not do the reverse. At 18 weeks they could do neither. Overall, the performance of girls was superior to that of boys. The findings are consistent with recent evidence suggesting that the ability to extract invariant configural information relative to the human face does not emerge until about 7 months of age.

Do Infants See Emotional Expressions in Static Faces

To determine whether young infants discriminate photographs of different emotions on an affect-relevant basis or on the basis of isolated features unrelated to emotion, groups of 17-, 23-, and 29-week-olds were habituated to slides of 8 women posing either Toothy Angry, Nontoothy Angry, or Nontoothy Smiling facial expressions and were then shown 2 new women in the familiarized expression and in a novel Toothy Smiling expression. At all 3 ages, recovery to the novel Toothy Smiling faces occurred only after habituation to Nontoothy faces (whether smiling or angry), not after habituation to Toothy Angry faces, indicating that infants had been responsive to nonspecific features of the photographs (presence or absence of bared teeth) rather than to affectively relevant configurations of features. In a second experiment, 2 older age groups (35 and 41 weeks) also proved to be insensitive to affect-related aspects of still faces, though more so for angry than for happy expressions. It is suggested that the young infants difficulty in extracting emotional information from static stimuli may be attributable to the absence of the critical invariants (dynamic, multimodally specified) that characterize naturalistic expressions of emotion.

The effects of repeated exposure and stimulus complexity on visual fixation in infants

Two groups of 3-1/2 month-olds each received two sessions of successive exposure to variable and repeated stimuli. Complexity of the repeated stimulus differed between groups and across sessions. Repetition produced significant fixation decrement which was reliably greater for the simple than for the complex stimulus. In all instances significant response recovery occurred with stimulus change.

Degree of stimulus complexity and habituation of visual fixation in infants

Three groups of 3 1/2-month-old infants were presented with varying and repeated exposures of visual stimili. For each group a different checkerboard pattern, i.e., 2x2, 12 x 12, or 24 x 24, served as the repeated stimulus. Visual fixation of each pattern declined significantly both during repetition and upon subsequent reexposure, the amount varying inversely with the complexity of the stimulus. In addition, infant girls showed steeper decrements than boys.

Infant Sensitivity to Deviations in Dynamic Facial--Vocal Displays: The Role of Eye Regard.

Do young infants appreciate the intentionality of adult interactors? In view of recent speculation that infants are innately sensitive to eye direction and that communicative intent is conveyed in part by attentional cues, the reactions of 3- and 5-month infants were compared to video episodes of normally responsive women who either appeared or did not appear to make eye contact. Across three experiments, lack of eye contact was achieved by either averting the eyes (E), averting the head and eyes (H&E), closing the eyes (ECL), or averting the head alone (H). Three-month-olds smiled less at H&E, H, and ECL, but not at E, relative to frontal faces, indicating sensitivity to head but not to eye orientation. By contrast, 5-month-olds smiled less at H&E, E, and ECL, but not at H, indicating sensitivity to both head and eye orientation. The implications of the data for mentalist views of infant social behavior are discussed.