Social Touch is associated with Neural but not Physiological Synchrony in Naturalistic Mother-Infant Interactions

Abstract

Caregiver touch plays a vital role in infants’ growth and development across mammalian species, yet its potential role as a communicative signal in human parent-infant interactions has been sparsely investigated this far. We assessed whether touch enhances neural and physiological synchrony in caregiver-infant dyads. We simultaneously measured brain activity (through functional near-infrared spectroscopy) and respiratory sinus arrhythmia (through electrocardiography) of 69 4- to 6-month-old infants and their mothers in distal and proximate non-interactive conditions vs. an interactive condition. Findings revealed that neural synchrony was highest during the interaction, next in the proximate, and lowest in the distal non-interactive condition. Physiological synchrony was highest during the interaction and lower in both non-interactive conditions. Furthermore, maternal affectionate touch during the interaction was positively related to neural but not physiological synchrony. This is the first evidence showing that touch mediates mutual attunement of brain activities in infants and their caregivers in naturalistic interactions.