Mother-infant interactive processes and infant behavioral and vagal stress recovery: Associations at 3, 6, and 9 months of age.

Mother-infant interactive processes, including matching social behaviors and repairing interactive ruptures, are proposed to foster infant stress functioning. However, little is known about the extent to which the concurrent relations between these dyadic processes and infant behavioral and vagal stress recovery change over the first year of life. In this study, 116 mother-infant dyads (55 girls) from a midwestern city in the United States completed the still-face paradigm at 3, 6, and 9 months. Using microcoding of infant and maternal behaviors (i.e., facial expressions, vocalizations, and gaze directions), we defined two dyadic states (positive match and mismatch) and measured dyadic matching as a composite of (a) the proportion of positive match and (b) latency to interactive repair (i.e., the average duration of mismatches), for the play and reunion episode, separately, at each time point. Infant behavioral and vagal stress recovery were assessed as the proportion of social engagement during the reunion episode and increases in respiratory sinus arrhythmia from the still-face to reunion episodes, respectively. At 6 and 9 months, higher levels of dyadic matching during the play episode were related to better infant behavioral and vagal stress recovery, controlling for matching during the reunion episode. At 3 months, the relation only emerged for infant behavioral stress recovery. These findings suggest that the dynamics of mother-infant interaction may play a key role in infant stress recovery, particularly during the second half of the first year when infants become more actively engaged in social interactions and their vagal systems become more mature. (PsycInfo Database Record (c) 2025 APA, all rights reserved).