Playing Together Synchronizes Mother-Child Autonomic Systems

The wonder increases when we realize that the system is open, engaging in free exchange with the outer world and that the structure itself is not permanent but is being continuously broken down by wear and tear of action and is continuously built up again by processes of repair. —Walter Bradford Cannon, explaining updated concepts of milieu intérieur in The Wisdom of the Body (1932)

Source: Марина Вельможко/Pixabay

In times of distress or social isolation, the human autonomic nervous system triggers a "fight-or-flight" stress response that can be measured by gauging changes in respiratory sinus arrhythmia (RSA), which is directly linked to vagus nerve engagement or withdrawal.

When someone feels happy, calm, or socially connected, the vagus nerve tends to engage in a way that increases the interval between heartbeats and results in higher heart rate variability (HRV).

RSA/HRV are widely used as markers for parasympathetic (rest-and-digest) activity and as indices of emotion regulation. Higher HRV (or increased RSA) indicates a robust parasympathetic response. Changes in RSA are an evidence-based way to monitor someone's internal psychophysiological state (i.e., milieu intérieur).

When people are having fun and in a good mood during interactive play or hack their vagus nerve vis-à-vis longer exhalations, increased RSA reflects less sympathetic (fight-or-flight) nervous system activity. On the flip side, stress-related autonomic nervous system responses are marked by vagal withdrawal and decreased RSA, indicating reduced parasympathetic activity.

A recent study (Suga et al., 2019) on the enhancement of HRV in mother-infant dyads found that when new moms practiced slow-paced diaphragmatic breathing techniques while holding their child, an infant's parasympathetic nervous system coordinated with mom's milieu intérieur as indexed by higher HRV.

This study suggests that when an infant's parasympathetic nervous system coordinates with mom's "rest-and-digest" physiological state, it fortifies vagal tone and promotes healthy socioemotional development.

Mother-Child Play Coordinates a Kid's Parasympathetic Nervous System—If Mom Is Connecting Emotionally

Another new study of mother-child dyads by researchers at the University of Illinois found that during high levels of behavioral coordination during play, a child's physiological state (as indexed by RSA) synchronizes with mom's heart rate variability. This paper (Hu et al., 2021) was recently published in the peer-reviewed journal Developmental Psychobiology.

These findings by first author Yannan Hu and colleagues suggest that when moms play with their kids and lead the charge with responsive communication, it promotes healthy socioemotional development by engaging a child's parasympathetic nervous system via the vagus nerve.

"Our study measures real-time physiological and behavioral coordination between mothers and children while they're interacting with each other," Hu said in a news release. "Researchers consider physiological synchrony beneficial for the child's socioemotional development. But our study is one of the first to link it to behavioral synchrony."

For this study, Hu et al. recruited 110 mothers with a child between the ages of three and five. In a behavioral lab, mother-child pairs played together for five minutes trying to solve a 3-D puzzle and then spent five minutes of "pretend play" with toys and stuffed animals.

During these interactive play sessions, the mother and child each wore a wireless device that measured parasympathetic responses by monitoring changes in heart rate variability via RSA indices. Trained observers also watched the play sessions and coded mother-child behavioral coordination in real-time, and took notes on exactly when a mother-child dyad responded to one another's social cues by laughing or sharing smiles.

"From a biobehavioral framework, mother-child physiological and behavioral coordination are interdependent processes that contribute to children's socioemotional development," the authors explained.

Emotional Disconnection Throws Off Physiological Coordination

After these interactive play sessions were completed, the researchers compared how behavioral coordination between mother and child synced up with their physiological coordination. The researchers found that positive changes in RSA reflected that a mother-child pair was socially engaged.

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Conversely, decreases in RSA were observed when there was a stressor or conflict during the play session, and the mother-child dynamics weren't harmonious. Failing to take turns, interrupting one another, and not responding to social cues were all associated with increased "fight-or-flight" stress responses in the mother's and child's autonomic nervous systems.

"We measured in real-time whether the mom and child are able to coordinate. This tells us about their interactions above and beyond the mom's parenting behavior," Hu explained. "It not only matters how parents treat their children. Children also need to be responsive to their parents' cues for the parent and child to establish a coordinated interaction."

"Research often focuses on how parents help children regulate negative emotions and behaviors, and this is important," senior co-author Nancy McElwain added. "It is equally important, though, to understand how parents and children work together to maintain or increase shared positive interactions and emotions. Play provides an ideal context to understand these positive processes."

The latest (2021) research on mother-child physiological coordination during interactive play suggests that parents can promote healthier socioemotional development on a physiological level by coordinating positive behaviors (e.g., taking turns, smiling at one another) while playing with their kids.

When parents connect with their children emotionally through play, it can trigger changes in a child's nervous system associated with robust parasympathetic activity and a lack of vagal withdrawal.

"From the findings, parents can learn more about the importance of tuning in to their children's cues and being responsive to their behaviors during playtime and other interactions," Hu concluded.