Breast milk may be the key to mother-baby bonding, according to research that found that breast-feeding mothers demonstrate stronger brain responses when they hear their baby cry. They're also more likely than formula-feeding moms to bond with their babies, says a study published in the May issue of the Journal of Child Psychology and Psychiatry.
Researchers at the Child Study Center at Yale University performed functional MRIs (fMRIs) on nine breast-feeding moms and eight formula feeders about a month after their babies were born. Participants listened to clips of their own baby and an unknown child crying, as researchers analyzed which areas of their brains lit up. Breast-feeding mothers registered greater activity in the relevant brain regions than formula-feeding moms, although all mothers' brains reacted more in response to their own infant's cries than to an unknown's.
Although the sample was tiny, researchers say the study was the first to make a connection between brain activity and maternal behavior. Hormones may also play a role. Oxytocin, which is involved in breast-milk letdown, helps foster emotional bonding between infants and mothers; its levels are higher in breast-feeding moms.
Psychological factors can't be discounted either. "Moms who decide to breast-feed might be reflecting a general tendency of mothers to be more empathetic to their infants, or perhaps they were more able to bond easily with their fetus when they were making the decision about wanting to breast-feed," says lead researcher Pilyoung Kim, a developmental psychologist at the National Institutes of Mental Health who worked at Yale when the research was conducted.