Cardiac vagal tone indices of temperamental reactivity and behavioral regulation in young children.

The relation between two dimensions of vagal tone (Vna), indexed by a baseline measure of Vna and suppression of Vna and temperamental reactivity and behavioral regulation was investigated. Forty-one children were observed during a series of episodes designed to elicit temperamental reactivity and behavioral regulation. Heart rate was recorded during these baseline, positive, negative, and delay episodes, from which measures of vagal tone were computed. Across the entire sample, vagal tone decreased from the baseline episode to the three affect tasks. Baseline measures of vagal tone were related to the tendency to show a decrease in vagal tone: Children who consistently suppressed vagal tone (showed a decrease to all the affect tasks) had higher baseline vagal tone. Baseline vagal tone was related to temperamental reactivity for the positive and negative tasks, but not the delay tasks. Vagal suppression (vagal difference score) was related to several of the behavioral regulation strategies used by the children in the affect-eliciting situations. These findings are discussed in terms of the adaptive value of physiological regulation in the development of regulatory behaviors that may be critical to social development.