Soothing touch matters: Patterns of everyday mother-infant physical contact and their real-time physiological implications.

Physical contact between infants and caregivers is crucial for attachment development. Previous research shows that skin-to-skin contact after birth and frequent baby wearing in the first year predict secure attachment at 12-months. This relationship is thought to be mediated by the activation of infants' parasympathetic nervous system through caregiver touch. However, little is known about everyday touch behaviors and their impact on infants' real-time parasympathetic activity. Laboratory observations may not accurately represent real-world interactions, highlighting the need for ecologically valid studies. To address this, we examined everyday dyadic touch behaviors and their real-time effects on infant parasympathetic activation. We video recorded N = 28 infants (1-10 months old) and their mothers at home for behavioral analyses. All infants wore wireless ECG sensors (1024 Hz) during video recordings, and n = 21 infants had high-quality ECG data that could be used for Respiratory Sinus Arrhythmia analyses. We used a dynamic measure of RSA (updated every 200 ms) as an index for real-time parasympathetic activation. We found that dyads touch interactions at home involve short, though highly variable bouts of physical contact, that change with infant age. Younger infants spent more time remaining stationary during contact and receiving more soothing touch compared to older infants. Only soothing touch - i.e., rocking, patting, bouncing, or stroking- led to immediate, significant increases in parasympathetic activity (RSA), and this effect was driven by younger infants. This study provides new insights into the ecological patterns of touch in early development and the biobehavioral mechanisms promoting secure attachment.