Social Context Moderates Mother-Infant Affective Synchrony in Everyday Life: An Ecological Momentary Assessment Study

Mother-infant affective synchrony, the moment-to-moment matching of mothers’ and infants’ emotions, is usually studied within the dyad when alone, yet everyday caregiving unfolds across varied social contexts. This study examined how momentary close company (partner, family member, or friend) relates to maternal affect and synchrony. Between September 2022 and September 2025, 253 mothers of infants aged 3–24 months (M = 9.4 months; 52.6% female; 56.7% Hispanic or Latinx) in Los Angeles, USA, rated their own and their infant’s affect up to six times daily for up to 14 days. Maternal and infant affect covaried at the same moment (negative β = 0.24; positive β = 0.28). Mothers reported higher positive and lower negative affect with a close companion or infant than alone or with distant company (acquaintances, coworkers, strangers). Negative synchrony was weaker with a close companion present (β = -0.05), although close company was unrelated to infant distress. Close company was also linked to higher infant happiness (β = 0.05) but not positive synchrony. Supplementary analyses found no lagged negative-affect effects and no partner-versus-family difference in the moderation. Maternal distress symptoms predicted higher chronic negative affect and stronger negative-affect inertia but not within-dyad dynamics. Early coregulation may extend beyond the dyad to the wider caregiving network.