Those of us who have been in the field for decades may recall a particularly well-known photograph of two mothers sitting side-by-side, feeding their infants. In the dyad on the left of the photo, the mother is bottle-feeding her baby. In the dyad on the right, the baby is being fed at the breast. There are distinct differences in the two dyads: the bottle-feeding baby is not held close to the mother's body, and the bottle-feeding mother is frowning at the nursing mother next to her, who is holding her baby close and actively engaging with her baby, smiling and appearing to be talking to her infant as he nurses.

The following new study from China immediately brought to mind the above-mentioned photograph from decades ago. I have long been interested in Tronick's Still-Face Paradigm, and this new study is one of many that have utilized Tronick's Still-Face Paradigm over recent decades. Edward Tronick is a Distinguished University Professor of Psychology at the University of Massachusetts at Boston and is well-known for his body of work, including the development of his Still-Face Paradigm in the 1970s. Over the course of his career, Tronick has focused on the neurobehavioral and social-emotional development of infants and young children, parenting in the U.S. and other cultures, and infant-parent mental health.

The new study:

Title: Breastfeeding duration and vagal regulation of infants and mothers.

In: Early Human Development 2022 Aug;171:105620.

Authors: Qili Lan, Hongxia Li, Li Wang, Suying Chang.

doi: 10.1016/j.earlhumdev.2022.105620. Epub 2022 Jun 28.

Highlights:

- Vagal regulation, indexed by RSA (respiratory sinus arrhythmia, a component of heart rate variability), supports self-regulation and social engagement.

- Longer breastfeeding duration is associated with lower infant RSA throughout the still-face paradigm.

- Longer breastfeeding duration is associated with higher overall RSA levels in mothers throughout the still-face paradigm.

- Greater breastfeeding duration contributes to infant adaptive vagal regulation during an interaction.

Abstract: "Background: Vagal regulation within the parasympathetic nervous system supports self-regulation and social engagement. Research has suggested that early feeding practices may influence mother-infant vagal functioning. Aim: We aimed to examine the association between breastfeeding duration and mother-infant vagal regulation during an interaction. We hypothesized that breastfeeding duration would be positively associated with adaptive vagal regulation in infants and mothers. Method: 204 mother-infant dyads (infant mean age 6 months) completed the face-to-face still-face (FFSF) task. During the task, vagal regulation indexed by respiratory sinus arrhythmia (RSA, a component of heart rate variability) was calculated through continuously recorded electrocardiogram signals. Breastfeeding duration and demographic information were reported by mothers. Linear mixed models were adopted to estimate the associations between breastfeeding duration and repeated measures of RSA in infants and mothers throughout the FFSF. Results: Infants breastfed for a longer duration demonstrated lower RSA throughout the FFSF (B = −0.06, 95 % CI: −0.09 to −0.03), suggesting active physiological mobilization to engage in interaction and regulate distress. Mothers with longer breastfeeding duration displayed higher baseline RSA and higher overall RSA levels (higher vagal control) during the FFSF (B = 0.06, 95 % CI: 0.02 to 0.09), indicating a calmer and regulated state. Conclusion: Longer breastfeeding duration was associated with more adaptive mother-infant vagal regulation during the interaction, indicating a positive dose-response association. This finding reveals breastfeeding practice as a factor contributing to infant effective vagal regulation and further supports WHO recommendation on exclusive breastfeeding for the first 6 months and continuing breastfeeding to 24 months and beyond."

Abstract only: https://www.sciencedirect.com/science/article/abs/pii/S0378378222000834?via%3Dihub

Tronick's professional bio refers to his work in NICU populations and much more: https://www.umb.edu/academics/cla/faculty/edward_tronick

There are many published interviews in print and on video with Tronick discussing the Still-Face Paradigm and other aspects of mental health in parents and children. Here are a few:

https://www.psychhelp.com.au/what-does-the-still-face-experiment-teach-us-about-connection/

"Trusting Relationships Are Central to Children's Learning -- Lessons From Edward Tronick". Tronick discusses his goal to pursue how relationships affect children's development: "I [wanted] to understand what's going on in the exchange [between a parent and child] that allows a relationship to be 'good' or 'smooth.' What do these words mean? Can we describe them, and can we come to an understanding of that process?" https://www.huffpost.com/entry/trusting-relationships-ar_b_1123524

"Effects of Child Abuse Can Last a Lifetime: Watch the ‘Still Face’ Experiment to See Why" https://www.washingtonpost.com/blogs/she-the-people/wp/2013/09/16/affects-of-child-abuse-can-last-a-lifetime-watch-the-still-face-experiment-to-see-why/

Tronick's most recent book (2020), co-authored with Claudia M. Gold, M.D., is The Power of Discord: Why the Ups and Downs of Relationships Are the Secret to Building Intimacy, Resilience, and Trust. His 2007 book, The Neurobehavioral and Social Emotional Development of Infants and Children, is considered a tour de force according to a review in New England Psychologist.

Today's PubMed search using "still-face paradigm" yielded 439 results. https://pubmed.ncbi.nlm.nih.gov/?term=still+face+paradigm

A PubMed search using "Edward Tronick" yielded these results: https://pubmed.ncbi.nlm.nih.gov/?term=edward+tronick