Carrying your baby: why is it important?
News Editor: Tina Pentland
Many of us have experienced the daily or nightly routine pacing the floor to settle a distressed child and so it would come as no surprise to be told that human infants like to be carried. What would be a little more surprising, perhaps, is to learn that scientists have now come up with a reason for this – specifically, just why the calming response is invoked by carrying when nothing else seems to help. Their findings have wider implications for parenting education and better understanding the bonding process because, as Kumi Koroda of the RIKEN Brain Science Institute points out, “unsoothable crying is [a] major risk factor for child abuse”.
In order to investigate the physiological and neurological bases of infant calming, the researchers at RIKEN investigated the calming response during maternal carrying in human and mice babies in a world first study reported in the journal Current Biology. They found that the calming response to maternal carrying in mice is, in fact, a co-ordinated three-way mechanism involving sensory inputs to the brain that trigger a response which first suppresses involuntary movement or struggling (a clear sign of distress) and lowers the heart rate, to induce soothing.
The team set out to study the phenomenon, having observed that many mammal species, not just humans, carry their infant young to soothe them although to date no-one had investigated the physiological reasons for this. The first stage of the study involved using ECG to measure physiological changes in human infants. The measurements showed that carrying the baby immediately caused a rapid decrease in the infant’s heart rate at the same time as it stopped crying and ceased to struggle. These findings also demonstrated that, just as animal babies will adopt a classic relaxed posture and remain motionless, limbs flexed, when they are carried, importantly, carrying is the major factor in the calming response – just holding the baby was not sufficient to soothe the infant. In the next stage of the study the researchers discovered similar responses to maternal carrying in normal infant mice but, significantly, the calming response to touch and movement did not occur in mice that had been desensitised. They noted further that the absence of calming “hindered maternal rescue of the pups, suggesting a functional significance for the identified calming response”.
Mice babies like it too!
Baby mice are also soothed by carrying. Using a tiny ECG monitor, scientists at RIKEN Brain Science Institute discovered that the pups stopped involuntary movements and ceased ‘crying’ when they were picked up and carried.
Image courtesy RIKEN: 19 April, 2013.
This study sheds new light on social bonding mechanisms and attachment in mammals and the authors suggest that the calming response which they have now documented may even be a ‘conserved’ or innate component of mother-child interactions across mammal species.