This study examined whether maternal prosody predicted changes in infants’ biobehavioral state during the Still Face, a stressor in which the mother withdraws and reinstates social engagement.
Predictions based on Polyvagal Theory were used to inform the selection of frequency and spectro-temporal acoustic features that reflect prosodic features in humans. Results suggest specific vocal acoustic features of speech that are relevant for regulating infants’ biobehavioral state and demonstrate mother-infant bi-directional dynamics.