New moms, ever wonder why you just can't get enough of that baby? It might come down to your nose.
A small study shows that a pathway linked to the reward center of the brain becomes very active when women who just gave birth get a whiff of a newborn.
"The olfactory -- thus non-verbal and non-visual -- chemical signals for communication between mother and child are intense," Johannes Frasnelli, a postdoctoral researcher and lecturer at the University of Montreal's Department of Psychology, said in a press release. "What we have shown for the first time is that the odor of newborns, which is part of these signals, activates the neurological reward circuit in mothers," he said. "It is in fact the sating of desire."
The researchers tested newborn smells on 30 women. Half of the women had given birth three to six weeks before the experiment, and the other women did not have children. The smells were collected from pajamas that newborns were wearing two days after birth, and none of the babies belonged to the mothers in the experiment.
The women were asked to breathe in the odor. While both groups of women said they liked the smell, there was more activity in the "dopaminergic system of the caudate nucleus" of the brain in the new mothers. This area, which is located at the center of the brain, is responsible for reward processing and releases dopamine, a chemical messenger that encourages reward-motivated behaviors.
"This circuit makes us desire certain foods and causes addiction to tobacco and other drugs," Frasnelli explained. "Not all odors trigger this reaction. Only those associated with reward, such as food or satisfying a desire, cause this activation."
In simpler terms, this means that new moms craved newborn smell like it was delicious food.
The researchers believe that this response to the odor might have to do with how a mother-child bond develops. The mom's brain perceives having the child near as a reward, and this may encourage more maternal care activities like breast-feeding.
However, researchers were unsure if the new moms' brains were activated because of childbirth itself or if they developed the response because of their own positive experiences with their children. It was also unclear if this same effect happens to new fathers, because they were not included in this experiment.
"It is possible that childbirth causes hormonal changes that alter the reward circuit in the caudate nucleus, but it is also possible that experience plays a role," said Frasnelli.
The study was published in Frontiers in Psychology in September.