Multimodal correlates of socioemotional movie-watching and their associations with internalizing symptoms in childhood and adulthood.

Socioemotional skills emerge from coordinated behavioral, autonomic, and neural processes that continue to reorganize across development, yet how these systems jointly support emotion processing and mental health remains unclear. Using a naturalistic movie-watching paradigm, we integrated behavioral, cardiac, and fMRI measures in children (6-14 years) and adults (18-29 years), alongside independent ratings of experienced valence and arousal. Across age groups, positive and negative emotional content elicited changes in subjective experience, heart rate, and corticolimbic activity, including the amygdala, hippocampus, and prefrontal cortex. Despite these shared patterns, group differences emerged. Children reported more positive affect, showed larger heart-rate deceleration, and exhibited stronger recruitment of thalamic and lateral prefrontal regions, areas previously linked to sensory integration and cognitive control. Adults, in contrast, showed greater activation in hippocampal and posterior midline regions, which have previously been associated with memory and self-referential appraisal. During negative emotional content specifically, children preferentially engaged medial prefrontal regions, whereas adults engaged lateral prefrontal regions. Importantly, in adults but not children, models combining behavioral, cardiac, and neural indices explained substantially more variance in internalizing symptoms than any single modality alone. Together, these findings demonstrate that socioemotional experiences evoke coordinated behavioral, autonomic, and neural responses across development, while also revealing age-group differences in their organization and associations with mental well-being.