Do you ever wonder why there seems to be such a strong bond between a mother and her baby? A new study shows that when a mom looks, smiles, and talks to her baby, the baby's heart rhythm instantly synchronizes with the mother's heart rhythm. The study shows for the first time that a mother's social interaction, such as smiling and making happy sounds, has a strong physical effect on her baby.
Hearts beat together
Psychologists have known for some time that affectionate handling and smiling at a baby leads to healthy development. Ruth Feldman at Bar-Ilan University in Israel wanted to find out if a social interaction, such as a mother smiling and talking to her baby, causes physical changes in mother or child. Forty mothers and their 3-month-old babies were set across from each other and cardiac output was measured by pasting electrodes next to their hearts. When mothers and their babies looked at each other and smiled, the mothers' and babies' hearts synchronized, beating with the same rhythm. The heart beat synchronization only worked with mothers and their own babies and only when the mother smiled and made happy sounds. The researchers believe that the social interaction between mother and baby causes changes in the brain, and one of these changes involves the regulation of heart rhythm.
What about fathers?
In the heart rhythm study only mothers and their babies were tested, but other studies have shown that fathers can also form a bond with their babies. Oxytocin, the bonding hormone, goes up in both mothers and fathers during parenting, even when mothers and fathers interact differently with their babies.
Synchronization is critical
In another study, researchers made videos of mother-infant interactions at home. Then they played the videos for the mothers and measured oxytocin levels and looked at brain regions of the mothers while they were watching their own mother-infant interaction videos. Mothers who were more attuned to the signals coming from their babies or were more synchronized, had higher levels of oxytocin and different brain regions were activated compared to the oxytocin levels and brain regions activated in non-synchronous mothers. Non-synchronized mothers were more anxious and intrusive in their interactions with their babies. For example, non-synchronized mothers tried to interact with their babies when their babies were trying to go to sleep or were asleep. Studies also suggest that depressed mothers have a negative effect on later social development of the child.
Feldman, R. et al. Mother and infant coordinate heart rhythms through episodes of interaction synchrony. Infant Behavior and Development (2011) 34, 569