Infant state: Relationship to heart rate, behavioral response and response decrement

The relationship of state to HR and behavioral responding to white noise stimulation was investigated in 2-week old infants. Results indicated that state is a potent determinant of various behavioral and HR phenomena. State was related to prestimulus HR levels. Cardiac responses elicited in active sleep were larger than those elicited in quite awake, even after prestimulus effects on responding were partialled out. Infants who were asleep throughout testing (group I) showed rapid behavioral and large HR response decrement. Infants whose state changed from active sleep to awake (group II), from quiet awake to asleep (group III), and from quiet awake to crying (group IV), showed significantly slower behavioral response decrement than those in group I, but behavioral response decrement was nevertheless evident in all groups. Cardiac response over trials also was examined in these 4 groups.