Abstract
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’ emotional expressions. Thirty first-time mothers viewed films of their own 6- to 7-month-old infants’ 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’s 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.
Highlights
Parenting always involves exposure to a series of infant expressions, reflective of negative and positive emotions, which are accompanied by maternal physiological and psychological arousal. How are such maternal responses modulated? The aim of this study was to examine a possible undoing effect of infant smiling on physiological and psychological maternal arousal caused by infant distress cries
We predicted that when mothers saw the happy smiling of their infants after previously being exposed to infant distress, sympathetic nervous system activity would be suppressed more rapidly than when the mothers experienced neutral expressions
The results showed no clear effect on subjective self-reports of emotional feelings (PANAS) as a function of which video, smiling or neutral, was viewed
Summary
From the very first stage of the postpartum period, human caregivers and infants show unique forms of emotional interaction [1]. Infants show various emotional expressions such as crying and smiling, and their caregivers typically respond sensitively and automatically to these expressions. Many studies using various methodologies have investigated maternal physical and mental responses toward infants’ emotional expressions. Distress cries of infants evoke physiological responses in mothers, most of which involve accelerated cardiac activity, increased skin conductance, and a higher rate of respiration [2,3,4,5,6]. Several researchers have suggested that this physiological arousal caused by infant cries functions as ‘preparation for PLOS ONE | DOI:10.1371/journal.pone.0129672 June 11, 2015
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