Effects of fatigue on infant emotional reactivity and regulation

The purpose of the present study was to examine 14- to 16-month-old infants' emotional reactivity and use of behavioral strategies for regulating distress during states of both alert wakefulness and fatigue. Twenty infants were tested at a time when their mothers expected them to be awake and alert, and twenty infants were tested at the time when their morning or afternoon nap typically began. Infants were observed responding to five mildly stressful episodes in their homes. Fatigued infants were more distressed than alert infants by separation from their mother and by being prevented from handling an attractive toy. Fatigued infants also engaged in fewer mature regulatory behaviors and more immature regulatory behaviors during the episodes. The infants' experiences with nonparental child care also were associated with their emotional reactivity. The relevance of these findings to parents and researchers and the benefits to infants of learning to handle stress when fatigued are discussed.