Respiratory sinus arrhythmia (RSA) dynamics matter for children's emotion regulation: RSA inertia and instability within a stress task.

The present study employed two key dynamic indicators (i.e., inertia and instability) to the psychophysiological research of child emotion regulation (ER) and examined whether respiratory sinus arrhythmia (RSA) dynamics were associated with child ER during a stress task. Eighty-nine Chinese school-age children (M age  = 8.77 years, SD = 1.80 years; 46.1% girls) and their primary caregivers participated in the study. After controlling for RSA static reactivity, multiple regression analyses indicated that lower RSA inertia was related to fewer in-task negative emotions rated by children and their caregivers, and higher RSA instability was associated with better child trait ER. This study introduces physiological indicators of the dynamic aspects of parasympathetic activity to the study of child ER.