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Characteristics of infant laughter during the first six months of life
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Characteristics of Infant Laughter During the First Six Months of Life Hui-Chin Hsu, Eva E. Nwokah, & Alan Fogel Department of Psychology, University of Utah, Salt Lake City, UT 84112-0251 Infant cry and laughter are significant vocal signals used by infants to express their negative and positive emotionality. Compared to empirical studies on infant cries, very little attention has been paid to infant laughter as an affective communicative component during a social interaction. Traditionally, experimental procedures are employed to investigate adults’ and children’s laughter, in which laughs are elicited by humorous stimulus such as comedy video and canned laughter. With a few exceptions, spontaneous laughter occurring in a social context was examined. This study, therefore, was to investigate the characteristics of young infants’ spontaneous laughter during a social interaction with their mothers. Thirteen infants and their mothers were videotaped weekly during a face-to-face interaction for approximately 5 minutes from age 4 to 24 weeks in a laboratory. The on- and off-set times of infant laugh vocalizations (sounds that are short, staccato, often interrupted by the abrupt closing of the vocal folds and that are accompanied by an active smile) were identified from videotapes. The characteristics of each infant laughs were coded based on the perceived intensity (comment: one peak (38%). chuckle: two peaks (19%), or rhythmical: more than two peaks (43%)), melodic contour (simple (45%) or complex (55%)), and its relation to mothers’ or infants’ own laughter sequence (isolated (44%). selfrepetitive (33%), or dyadic (23%)). In addition to infant gaze direction (gaze at mother (78%) or not) and maternal facial expression (smiling (79%) or not), the associated physical context variable such as infant postural position (supine (21 X), recline (18%), and upright (61%)) and social context variable such as dyadic activity (social (41 R) or tactile (59%) game) were also coded. A total of 175 infant laughs were identified. The average length of these laughs was approximately 1.1 sets. The duration of these laughs did not vary according to infant postural position, infant gaze direction, maternal positive expression, dyadic activity, or laughter sequence. However, infant laughs were longer when they were characterized by complex melodic contour, ~(1,173)=22.90, p< .OOOl, or higher intensity, IJ2,172)=16.93, p< .OOOl. To examine the relationship among the characteristics of infant laughter, two sets of Log-linear Analysis and follow-up Configural Frequency Analysis were performed separately. The first set of analyses examined the relationship between infant laughter intensity, melodic contour, and laughter sequence. The results showed that the best fitting model included three 2-way interactions terms: Laughter Intensity x Melodic Contour, Laughter Intensity x Laughter Sequence, and Laughter Sequence x Melodic Contour, c*(4) = , E < .35. The follow-up analysis revealed that comment laughs were more likely to be isolated with simple melodic contour, ~=2.85, p< .004, and less likely to be reciprocal with complex melodic contours, z--3.64, p< .002. The second set of analyses examined the relationship between infant laughter intensity, physical context, and social context. The results showed that the best fitting model included two 2-way interaction terms: Laughter Intensity x Dyadic Activity and Postural Position x Dyadic Activity, Q(7)=, a< .20. The follow-up analysis revealed that comment laughs were more likely to occur when infants engaged in social games with their mothers in recline position, ~=5.90, p< .OOOl,and less likely to happen when infants engaged in tactile games with their mothers in recline position, z =-3.55, p< .002. Chuckle laughs were more likely when the dyads engaged in tactile games in supine position, g=2.63, p< .Ol. In addition, rhythmical laughs were more likely to occur when infants engaged in tactile games with their mothers in upright position, g = 5.12, p < .003. In conclusion, this study demonstrated that young infants’ laughter are complex context-dependent phenomena embedded in a dynamic interactive process.
Characteristics of Infant Laughter During the First Six Months of Life Hui-Chin Hsu, Eva E. Nwokah, & Alan Fogel Department of Psychology, University of Utah, Salt Lake City, UT 84112-0251 Infant cry and laughter are significant vocal signals used by infants to express their negative and positive emotionality. Compared to empirical studies on infant cries, very little attention has been paid to infant laughter as an affective communicative component during a social interaction. Traditionally, experimental procedures are employed to investigate adults’ and children’s laughter, in which laughs are elicited by humorous stimulus such as comedy video and canned laughter. With a few exceptions, spontaneous laughter occurring in a social context was examined. This study, therefore, was to investigate the characteristics of young infants’ spontaneous laughter during a social interaction with their mothers. Thirteen infants and their mothers were videotaped weekly during a face-to-face interaction for approximately 5 minutes from age 4 to 24 weeks in a laboratory. The on- and off-set times of infant laugh vocalizations (sounds that are short, staccato, often interrupted by the abrupt closing of the vocal folds and that are accompanied by an active smile) were identified from videotapes. The characteristics of each infant laughs were coded based on the perceived intensity (comment: one peak (38%). chuckle: two peaks (19%), or rhythmical: more than two peaks (43%)), melodic contour (simple (45%) or complex (55%)), and its relation to mothers’ or infants’ own laughter sequence (isolated (44%). selfrepetitive (33%), or dyadic (23%)). In addition to infant gaze direction (gaze at mother (78%) or not) and maternal facial expression (smiling (79%) or not), the associated physical context variable such as infant postural position (supine (21 X), recline (18%), and upright (61%)) and social context variable such as dyadic activity (social (41 R) or tactile (59%) game) were also coded. A total of 175 infant laughs were identified. The average length of these laughs was approximately 1.1 sets. The duration of these laughs did not vary according to infant postural position, infant gaze direction, maternal positive expression, dyadic activity, or laughter sequence. However, infant laughs were longer when they were characterized by complex melodic contour, ~(1,173)=22.90, p< .OOOl, or higher intensity, IJ2,172)=16.93, p< .OOOl. To examine the relationship among the characteristics of infant laughter, two sets of Log-linear Analysis and follow-up Configural Frequency Analysis were performed separately. The first set of analyses examined the relationship between infant laughter intensity, melodic contour, and laughter sequence. The results showed that the best fitting model included three 2-way interactions terms: Laughter Intensity x Melodic Contour, Laughter Intensity x Laughter Sequence, and Laughter Sequence x Melodic Contour, c*(4) = , E < .35. The follow-up analysis revealed that comment laughs were more likely to be isolated with simple melodic contour, ~=2.85, p< .004, and less likely to be reciprocal with complex melodic contours, z--3.64, p< .002. The second set of analyses examined the relationship between infant laughter intensity, physical context, and social context. The results showed that the best fitting model included two 2-way interaction terms: Laughter Intensity x Dyadic Activity and Postural Position x Dyadic Activity, Q(7)=, a< .20. The follow-up analysis revealed that comment laughs were more likely to occur when infants engaged in social games with their mothers in recline position, ~=5.90, p< .OOOl,and less likely to happen when infants engaged in tactile games with their mothers in recline position, z =-3.55, p< .002. Chuckle laughs were more likely when the dyads engaged in tactile games in supine position, g=2.63, p< .Ol. In addition, rhythmical laughs were more likely to occur when infants engaged in tactile games with their mothers in upright position, g = 5.12, p < .003. In conclusion, this study demonstrated that young infants’ laughter are complex context-dependent phenomena embedded in a dynamic interactive process.