Why crying babies become calm and relaxed upon being carried
11 September, 2013
ISLAMABAD: Mothers often carry their crying babies, pacing the floor, to help them calm down, and most of the time it's very effective.
Now, a new research has revealed the science behind it - infants experience an automatic calming reaction upon being carried, whether they are mouse or human babies. The study is the first to show that the infant calming response to carrying is a coordinated set of central, motor, and cardiac regulations and an evolutionarily conserved component of mother-infant interactions, the researchers said.
It might also explain a frustrating reality for new parents: that calm and relaxed very young children will so often start crying again just as soon as they are put back down.
"From humans to mice, mammalian infants become calm and relaxed when they are carried by their mother. This infant response reduces the maternal burden of carrying and is beneficial for both the mother and the infant," said Kumi Kuroda of the RIKEN Brain Science Institute in Saitama, Japan.
In other words, a mother's arms really are the best place for a young baby to be in terms of his or her chances of survival. And mothers certainly appreciate a calm and relaxed baby. That babies naturally stop crying when they are carried is an evolutionary win-win.
Kuroda and her colleagues found in careful tests that the heart rates of human babies slow immediately upon carrying. After they managed to find ECG monitor electrodes small enough to use on conscious mouse pups, the researchers found that the same goes for mice.
Both mouse and human babies also stop moving when they are carried. And when baby mice are carried, their ultrasonic cries stop, too.
The researchers traced that response in the mice to a sense known as proprioception, the way that information about body movements is perceived. They also found that particular parts of the brain and parasympathetic nervous system are key in mediating the coordinated response to carrying.
The findings have important implications for parenting and may even play a role in preventing child abuse, the researchers said, by helping grownups see things from an infant's point of view.
The research has been published in the Cell Press journal Current Biology.