科学美国人60秒:Babies Just Want to Be Smiled at

Ever try to get a baby to smile? It can seem close to impossible—and then suddenly there it is: that elusive, seemingly joyous grin. Well it turns out those smiles aren’t spontaneous—they’re strategic.

Researchers have found that when babies smile, it's for a reason. They want whoever they’re interacting with—typically a parent—to smile back. And they time it just so, a smile here and a smile there. The researchers call it sophisticated timing. The study is in the journal PLoS ONE. [Paul Ruvolo, Daniel Messinger, Javier Movellan, Infants Time Their Smiles to Make Their Moms Smile]

The researchers enlisted real mothers and infants and quantified their interactions, which fell into four categories. One: babies wanted to maximize the amount of time smiling at their mothers. Two: they wanted to maximize the time the mothers smiled at them. Three: they wanted to experience simultaneous smiling, and four: no smiling at all.

By studying when smiles happened and what the subsequent effect was, the investigators were able to figure out that for mothers the goal 70 percent of the time was to be smiling simultaneously—while for babies 80 percent of the time they just wanted their mother smiling at them. So, mothers want the interaction, while babies just want to be smiled at.

So your baby may not be able to feed itself, talk or even turn over yet. But when it comes to smiles, babies seem to know exactly what they're up to.

—Erika Beras