Within-mother variability in vagal functioning and concurrent socioemotional dysregulation.

During dyadic interactions, well-regulated autonomic responses may support and be supported by socioemotional regulation, whereas autonomic responses that are inappropriate for the social context may be linked with socioemotional dysregulation. We evaluated women's parasympathetic and socioemotional responses during playful interaction with their 24-week-old infants, hypothesizing that insufficient or excessive variability in second-by-second vagal functioning would be associated with concurrent socioemotional dysregulation. Among a sample of 322 low-income, Mexican origin mothers (Mage  = 27.8; SD = 6.5 years), variability in second-by-second vagal functioning was indexed by within-mother standard deviation (SD) in respiratory sinus arrhythmia (RSA) during a 5-min unstructured play task. A latent construct of socioemotional dysregulation was identified using factor analyses. Structural equation modeling was used to evaluate linear and quadratic relations between within-mother SD of RSA and concurrent socioemotional dysregulation. Analyses revealed a positively accelerated relationship between within-mother SD of RSA and concurrent maternal socioemotional dysregulation during play with her infant. Within-mother SD of RSA during a non-interactive baseline task was not related to maternal dysregulation. The results illustrate mothers' dynamic autonomic and socioemotional responses are intertwined during real-time interactions with her infant and lend support for the discriminant validity of within-mother SD of RSA during free play.