After months of teetering back and forth like an air dancer in a derecho, you’ve finally done it: you can now support yourself sitting up. In a few short months you’ll be shuffling about on your hands and knees, drawn to a tantalizingly three-dimensional world of sharp edges and harrowing stairwells. But for now, it’s all you can do to sit back in your diapers and take in the new—upright—view.
And what a momentous view it is. According to a new study led by Cara Cashon of the University of Louisville, the change in vantage point may even trigger a change in how you perceive faces.
Faces are, of course, the best places to learn about a person: who she is, how she’s feeling, and whether she’s about to take your cookie. From birth, infants are highly attuned to faces, preferring to stare at them over just about anything else. Infants are also terrific at recognizing individual faces. By about three to four months, they’ve acquired what’s known as “holistic facial processing”—the ability to perceive individual faces not as bundles of chins and eyes and noses, but as relationships between sets of chins and eyes and noses. At this age, babies aren’t too picky about what counts as a meaningful face: even inverted faces are recognized holistically.
Then, right around their half birthday, something odd happens. Infants lose their holistic processing superpowers—only to regain them for upright, but not inverted, faces a month or so later. What the what?
Losing an ability only to regain it in a different, adult-like form is, it turns out, not that uncommon. Infants on the cusp of walking suddenly regress in their ability to sit upright or grasp objects using a single hand. Children who once said went and ate regress to saying go-ed and eated along the winding path toward verb mastery. Underlying these “two steps forward, one step back” trajectories seems to be a need to reset, or otherwise adjust, a way of navigating the world that just isn’t hacking it anymore.
Which brings us back to seeing faces. Might a similar reorganization of the facial recognition system—one geared toward prioritizing upright faces over inverted ones—be triggered by the ability to sit up and, well, understand upright faces in a new way?
Cashon and her colleagues suspected as much. Indeed, babies’ sitting abilities improve right around the age when their holistic processing regresses. But in order to make a convincing case for a relationship between sitting and perceiving, the researchers had to go one step further.
They recruited 111 infants, some just under six months, and the rest just over. Younger infants were composed of “nonsitters” as well as “near sitters” (who couldn’t yet support themselves for longer than 10 seconds). Older infants were composed of “new sitters” (who’d just recently mastered the feat) and “expert sitters” (who had been sitting prettily for at least a month).
Infants saw a sequence of human faces on a large monitor. Once they’d sufficiently lost interest—as evidenced by their looking away—they were shown a new sequence that included both a familiar face and a composite face Photoshopped to combine features from two familiar faces. The idea: only infants able to process faces holistically should be drawn to the composite face—so novel and intriguing!—over the familiar one.
Sure enough, both the young “nonsitters” and the older “expert sitters” looked longer at the composite face, signaling interest in the new arrangement of features. But the younger “near sitters” and the older “new sitters”—those on or past the brink of acquiring, but not yet accustomed to, an upright posture—did not. Sitting ability, in other words, better predicted face recognition than age did.
The study does not rule out the possibility that some third factor is responsible for both developmental changes—children with physical (but not mental) delays could provide some answers here. Nonetheless, the relationship highlights just how tightly our perceptions of the world are coupled with the body we were given to explore it.
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