Early development of behavioral and emotional regulation in irritable infants as expressed in sleep, temperament and crying rhythms

Date of Completion

January 2000


Psychology, Psychobiology|Psychology, Behavioral|Psychology, Developmental




The development of sleeping and crying rhythms was studied in a group of irritable infants. Sleeping patterns were obtained using the Motility Monitoring System, which records the sleep of the infant unobtrusively when he or she is in his or her own crib at home. The crying data were obtained using a cry recording system, which records crying vocalizations, onto audio cassette tapes. Finally, the temperament data were gathered using standardized temperament questionnaires, which were completed by the mother at several time points. ^ The first study investigated the sleep patterns of infants who did and did not cry with a diurnal rhythm over 2 successive days. It was found that infants who cried with a diurnal rhythm had sleep patterns that were suggestive of less stress at a later age. The second study measured infants' crying patterns over 3 successive days, instead of two. The timing of crying as related to temperament variables were significantly related. The third study compared crying rhythms over 24-hour periods with temperament characteristics from 2 different questionnaires. It was found that infants who were rated as less “negative” by their mothers had different temporal patterns of crying over the 24-hour day than those who were rated as more “negative”. The last study investigated the sleeping patterns of infants who regularly slept with their parents (known as “co-sleeping”), and those who rarely or never co-slept. It was found that infants who co-slept exhibited sleep in the crib that was suggestive of stress. ^ The results of these studies have several implications. Some infants are able to express their crying patterns into diurnal rhythms, which may have positive implications for the developing mother-infant system and may reflect a more mature nervous system. Also, crying that occurs during certain times of the day may somehow be considered less stressful for some mothers. Finally, since co-sleeping has previously been shown to cause sleep fragmentation, and results from this study suggest that infants may be reacting to that fragmentation and expressing stress in their sleeping patterns, it may be prudent to re-examine the common practice of co-sleeping in the developing infant. ^