It's not always easy to follow your heart. But for human babies and their mothers, following each other's hearts may be as simple as sharing a
smile. A new study shows that 3-month-old infants and their mothers can synchronize their heartbeats to mere milliseconds. Researchers sat 40
pairs of mothers and infants face-to-face, equipped with sticky skin electrodes on either side of their hearts. Beat for beat, mother-and-child hearts
thumped together almost instantly as they shared loving looks or contented coos. This cardiac coupling worked only for moms with their own babies, and
only when the duos synchronized smiles and other cheerful social behaviors, researchers report in this month's issue of Infant Behavior and Development. When humans mirror each other's facial expressions, they may switch on specific areas in the brain that tell
the heart when to thump, the researchers suspect. Melding with mom lasts longer than just a few beats, however. Babies who don't tune in with their
mothers are less empathetic as teenagers, according to previous
work from the same lab. Premature infants or those whose mothers have postpartum depression may be most at risk for losing this social skill because
they miss out on early opportunities to interact with mom.
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