Why Do Babies Cry?
Human infants are born into the world in a state of dependence that requires care from others. To seek out the attention they need, infants have a wide range of nonverbal capacities for communication, more than we often realize. Crying is the most obvious – and often most effective – way that babies elicit attention and care. In spite of the adaptive advantage of crying as a tool for infants to get the care needed for survival, infant crying can be distressing to all parties involved, and possible lead to caregivers to seeking out professional advice. Therefore, an understanding of why infants cry and how to decrease crying is of high importance to the medical, scientific, and parenting communities.
Frequency of infant crying
Many parents express the sentiment that their baby must cry more than average. Though individual differences in crying levels do exist, the majority of U.S. infants follow a fairly common trajectory of crying frequency and duration over the first few months of life, characterized by a gradual increase peaking at around the six week mark followed by slow decrease as infants approach their fourth month of life. However, ethnographic descriptions of infant behavior outside of the Western, industrialized world consistently document lower levels of crying and increased time in quiet, alert states. In comparison with the infants reported in studies of Western developmental science, considerably lower levels of crying are reported among infants in non-Western, non-industrialized societies, including the Akaand !Kung San hunter-gatherer societies of Africa.
What explains cultural variation in crying?
Cultural variation in environment, diet, healthcare, and community structure, among other variables, make it difficult to draw specific conclusions about the causes of cultural differences in infant behavior. However, the societies with the lowest known levels of infant distress all share an important characteristic: proximal caregiving. Proximal caregiving is characterized by near-constant physical contact with caregivers, breastfeeding on demand, and co-sleeping. In particular, carrying style (i.e., carrying in arms for the majority of the day or wearing the baby in a sling) has explicitly been reported by mothers in these communities as a strategy for regulating infant distress.
What does this mean for infants and parents globally? Can the benefits of increased infant-caregiver physical contact in these societies transfer to industrialized cultures?
So far, the research says yes.
Among typically-developing infants in Western societies, increased physical contact with caregivers has been shown to decrease crying. Many studies highlight the effects of simple skin-to-skin contact (or “kangaroo care,” see blog posts HERE) on decreased crying. In fact, one systematic review of 30 skin-to-skin studies with over 30 participants showed a significant effect of post-partum skin-to-skin on crying frequency and duration. These effects carry over to physical contact without direct skin-to-skin contact among typically-developing babies. In one randomized controlled trial with 99 infants, those that were assigned to the increased carrying group cried 43% less than control infants at the 6-week period of peak crying. However, these results have not been consistently replicated. When infants were randomly assigned to a supplemental carrying intervention at birth, amount of crying assessed at 2-weeks, 6-weeks, and 12-weeks was not significantly different from the control group. One explanation for this disparity is that the experimental group only increased carrying by an average of 1-2 hours per day, reflecting a relatively mild amount of infant-caregiver physical contact in comparison with proximal care cultures who are in contact with infants over 80 percent of the day (e.g., the 10 plus hours of daytime holding plus nighttime co-sleeping observed in !Kung San infant-caregiver dyads).
One study addressed this disparity by studying a more dramatic increase in infant-caregiver physical contact. Parents in the UK who chose to adopt a proximal care parenting style classified by holding or carrying their baby over 80 percent of the day were compared with parents from London and Copenhagen who were using a conventional parenting style. Conventional Western infant care is characterized by feeding and sleeping routines, where infants are fed every 3-4 hours, kept in strollers, seats, or cots for much of the day, delayed response to crying, and separate sleeping in cribs. In contrast, proximal care is characterized by maintaining physical contact between infant and caregiver through carrying or babywearing, breastfeeding on demand, responding quickly to infant cues, and co-sleeping. Infants from the proximal care group cried significantly less than infants in the other two groups.
There are many ways to facilitate infant-caregiver physical contact, including skin-to-skin “kangaroo” care, babywearing, cosleeping, and infant massage, to name a few. So what is the best for decreasing crying and why?
Interestingly, carrying with movement seems to have a more profound effect than simply maintaining physical contact. In one study, six-month-old infants stopped crying, relaxed their body, and decreased their heart rate when held by their walking – but not sitting – mothers.
Because wearing your baby in a sling or wrap is proven to facilitate prolonged carrying – especially during locomotion – babywearing is one easy way to reap the benefits of having a less-distressed baby!
This Guest Blog was written by Emily E. Little, M.A.
Emily is a doctoral candidate in developmental psychology at University of California, San Diego. Her dissertation research examines the social mechanisms underlying the benefits of babywearing, including how increased mother-infant physical contact facilitates higher maternal responsiveness. Her research program more broadly investigates culturally-mediated mother-infant communication, and she has collected data on early teaching in Vanuatu, infant emotional displays in Bolivia, and breastfeeding patterns in Guatemala. She is also specializing in anthropogeny, or the study of human origins, through UCSD’s Center for Academic Research and Training in Anthropogeny (CARTA), which has added an evolutionary perspective to her interests in culture, mother-infant interaction, and babywearing. She is passionate about making a positive contribution in the communities where she works, not just in San Diego – where she volunteers as a Volunteer Babywearing Educator in training with Babywearing International – but also at her international fieldsites, where she volunteers at community health centers and raises money for maternal and infant health services.
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