Does cardiac vagal tone relate to behavioral reactivity and difficult temperament in infants and 3-year-olds?
Cardiac vagal tone in infancy is related to concurrent difficult temperament and predicts behavioral difficultness at 3 years of age.
Psychophysiological studies of infants have found a relation between behavioral reactivity and indices of autonomic state. The relation between behavioral reactivity, assessed via maternal report, and autonomic state, assessed via cardiac vagal tone in 9-month-old infants was examined. Cardiac vagal tone was quantified by measuring the amplitude of respiratory sinus arrhythmia. High cardiac vagal tone was associated with greater behavioral reactivity, resulting in maternal reports of more difficult temperament. Stability of the two measures, cardiac vagal tone and difficult temperament, from 9 months to 3 years of age was demonstrated. In addition, 9-month cardiac vagal tone, independent of 9-month temperament, was related to 3-year difficultness with higher 9-month cardiac vagal tone being related to less-difficult 3-year behavior.
Porges et al. (Fri,) studied this question.