Lag-sensitive cross-correlation analysis of mother-infant HF-HRV synchrony during free interaction: An exploratory feasibility study.

Caregiver-infant interaction involves coordinated behavioral and physiological processes. Heart rate variability (HRV) may provide a physiological index of these interactions. This study preliminarily evaluated an analytical approach for characterizing mother-infant HRV synchrony with temporal lags. Electrocardiograms were simultaneously recorded during free interaction. Thirty sessions were obtained from 15 mother-infant dyads, and 16 analyzable sessions from 10 unique dyads were included in the final analysis. Normalized cross-correlation analysis of high-frequency HRV was performed using MATLAB R2022b. Highly correlated intervals accounted for a mean of 75% of the analyzed interaction time, and positive and negative lags occurred in nearly equal proportions. Observed synchrony exceeded the session-specific surrogate distribution in 13 of 16 sessions based on the empirical p-value criterion. These findings support the feasibility of a lag-sensitive, surrogate-informed approach for preliminarily describing putative mother-infant HRV coordination during free interaction.