The Power of an Infant\u27s Smile: Maternal Physiological Responses to Infant Emotional Expressions

Infant emotional expressions, such as distress cries, evoke maternal physiological reactions. Most of which involve accelerated sympathetic nervous activity. Comparatively little is known about effects of positive infant expressions, such as happy smiles, on maternal physiological responses. This study investigated how physiological and psychological maternal states change in response to infants\u27 emotional expressions. Thirty first-time mothers viewed films of their own 6- to 7-month-old infants\u27 affective behavior. Each observed a video of a distress cry followed by a video showing one of two expressions (randomly assigned): a happy smiling face (smile condition) or a calm neutral face (neutral condition). Both before and after the session, participants completed a self-report inventory assessing their emotional states. The results of the self-report inventory revealed no effects of exposure to the infant videos. However, the mothers in the smile condition, but not in the neutral condition, showed deceleration of skin conductance. These findings demonstrate that the mothers who observed their infants smiling showed decreased sympathetic activity. We propose that an infant\u27s positive emotional expression may affect the branch of the maternal stress-response system that modulates the homeostatic balance of the sympathetic and parasympathetic nervous systems

Eight-month-old infants’ behavioural responses to peers’ emotions as related to the asymmetric frontal cortex activity

Infants are sensitive to and converge emotionally with peers’ distress. It is unclear whether these responses extend to positive affect and whether observing peer emotions motivates infants’ behaviors. This study investigates 8-month-olds’ asymmetric frontal EEG during peers’ cry and laughter, and its relation to approach and withdrawal behaviors. Participants observed videos of infant crying or laughing during two separate sessions. Frontal EEG alpha power was recorded during the first, while infants’ behaviors and emotional expressions were recorded during the second session. Facial and vocal expressions of affect suggest that infants converge emotionally with their peers’ distress, and, to a certain extent, with their happiness. At group level, the crying peer elicited right lateralized frontal activity. However, those infants with reduced right and increased left frontal activity in this situation, were more likely to approach their peer. Overall, 8-month-olds did not show asymmetric frontal activity in response to peer laughter. But, those infants who tended to look longer at their happy peer were more likely to respond with left lateralized frontal activity. The link between variations in left frontal activity and simple approach behaviors indicates the presence of a motivational dimension to infants’ responses to distressed peers

Happiness and Joy

Happiness and joy involve feelings of positive engagement which are prototypically expressed through the face, voice, and body. Joyful smiles tend to be strong and involve both eye constriction (the Duchenne marker) and mouth opening. Through approximately 2 months of age, joyful expressions are primarily rooted in physiological arousal. Positive emotional expressions then quickly become more social, occurring in face-to-face interactions with caregivers as infants increasingly derive psychological meaning from individuals and events. Beginning in the second half of the first year of life, infants’ expressions of positive emotion are increasingly incorporated into patterns of intentional communication. Between 1 and 2 years of age, positive expressivity is increasingly responsive to parental affective cues during pretense play. Preschoolers’ between 2 and 5 years of age utilize specific forms of positive emotion expressions to foster affiliation with their peers. By 8 years of age, children voluntarily control their expressions of positive emotion depending on the interpersonal context. These early expressions of joy are associated with later social competence, including reduced behavioral inhibition and reticence in reaction to novelty, compliance with parental requests, tolerance of new experiences, and attachment security. Further, positive expressivity is also linked to later life outcomes, primarily life satisfaction and overall well-being in adulthood. Positive emotion expression varies as a function of gender as well as cultural differences in the emotional significance and perceptions of positive expressions. Finally, the development of joyful expressivity is differentially sensitive to a variety of risk conditions, including maternal depression, prematurity, infant blindness, Down syndrome, and autism spectrum disorder