A baby’s smile can lighten mom's mood - research proves it.

The study, “What’s in a Smile? Maternal Brain Responses to Infant Facial Cues,” found photos of smiling infants triggered activity in the reward centers of their mothers’ brains.

Researchers used functional MRI to track the brain responses of 28 first-time mothers to photos of happy, neutral and sad infants’ faces.

When mothers saw photos of their own smiling baby, their brains lit up in areas associated with the neurotransmitter dopamine.

Babies with sad or neutral expressions triggered less of a reaction. Surprisingly, when shown a photo of a crying baby, the reaction was about the same whether it was the mother’s own child or an unknown child.

The findings could help scientists understand the neural basis of the mother-infant bond,