Inter-Brain Correlates of Coparenting During the Lausanne Trilogue Play

Coparenting refers to how caregivers coordinate their roles and behaviors in relation to the child, yet its neurophysiological correlates remain largely unexplored. This exploratory cross-sectional study examined whether caregiver-caregiver inter-brain synchrony (IBS) during the Lausanne Trilogue Play (LTP) was associated with observed coparental coordination and children's developmental outcomes. Eleven families with a preschool-aged child participated in a laboratory visit including triadic observation, caregiver questionnaires, and simultaneous electroencephalography (EEG) recording from both caregivers; EEG analyses were conducted in nine dyads. Coparental coordination was assessed using the Family Alliance Assessment Scales (FAAS), and child outcomes were measured with the Ages and Stages Questionnaires (ASQ-3) and Ages and Stages Questionnaires: Social-Emotional (ASQ:SE). Higher observed coparental coordination was associated with fewer socioemotional difficulties, whereas cognitive/problem-solving scores were more strongly related to caregiver education. Group-level IBS did not reliably exceed surrogate baselines derived from pseudo-dyads, although several dyads showed above-chance synchrony in selected conditions. Exploratory analyses further suggested that central beta synchrony during Phase 2 of the LTP was positively associated with observed coparental coordination, though these associations did not survive FDR correction. These findings provide preliminary support for studying coparenting as a multilevel process spanning behavioral and neural domains.