Long before most babies toddle or talk, they begin to make sophisticated inferences about the world around them. By as young as 3 months old, newborns can form expectations based on physical principles like gravity, speed, and momentum.

Scientists at several universities told me they now have evidence, to the likely delight of far-flung grandparents everywhere, that infants can also tell the difference between, say, a broadcast of Mister Rogers and a video call with their actual grandfather. The ability to discern between video broadcast and video-based chat from infancy, which researchers have only recently confirmed, could have a profound effect on our understanding of how the human brain develops—and specifically, how technologies can play a role in shaping abstract concepts early on.

“Babies who are pretty young are able to pick up, in particular, whether or not an adult is actually responding to them in real time,” said Elisabeth McClure, a researcher who focuses on children and media at Georgetown University. “Some television shows try to imitate this. You see, for example, with Elmo, or on Blue's Clue's, they look directly at the camera and pretend to interact with the child. There's evidence that babies can tell the difference as early as 6 months old.”

This is meaningful for a few reasons, not least of which is cultural. Extended families are increasingly spread across greater geographic distances. Video calls are how many babies first meet their grandparents, their aunts and uncles, and other people who love them. Video-chat technologies, then, have major implications for how humans perceive key relationships.

While interfaces like Skype, FaceTime, and Google Hangout are still relatively new, this area of research builds on decades of experiments involving children and electronic screens. Researchers have long studied how passive television viewing affects young children, and how well children can learn from watching educational programming, but scientists are only just beginning to figure out how babies understand screen interactions with another person in real time.

Michael Rich, the director of the Center on Media and Child Health and a pediatrics professor at Harvard Medical School, said that the latest findings help illustrate how the concept of “screen time” is too broad. “Given the plethora of screens and uses for those screens that we have now, I think that we have to be a little sanguine about how much we can extrapolate,” he said.

Of course, babies being babies, it’s hard to know what they’re thinking just by watching how they act. “Just because they stare at a screen doesn’t mean they are interpreting it, decoding it, understanding it,” Rich said. “Can a baby decode the pattern of light and dark on a two-dimensional object as a symbol of Grandma’s face, and perceive that the noise they hear is generated by Grandma talking to them?”

Back at Georgetown, McClure and her team conducted a survey across Washington, D.C., asking parents of infants and toddlers how many of them had ever participated in a video chat like FaceTime. “Eighty-five percent of the families that we surveyed who have babies under 2 said they had ever used it,” McClure said. “And almost 40 percent said they used it once a week. Not only are they using [this technology], but they use it a lot.”

And not only that—these chats were surprisingly long, often lasting for 20 minutes or more. And many parents of young children reported using video chat with their kids even though the kids weren’t allowed to watch television. “Even families who avoid video exposure,” McClure said, “they make an exception for video chat.”

As a doctoral student, McClure spent much of her time observing families with their babies during these video calls. In particular, she wanted to assess how they coped with the limitations of streaming video chat, which can be glitchy and inconsistent. Even when the conversations are technologically flawless, the format itself disrupts many of the cues that help babies understand what’s going on in a face-to-face interaction. “Babies are very sensitive to eye contact, physical contact, pointing at things, and all of those can be compromised,” McClure said.

For example, babies watching television or movies tend to be confused when broadcast sound is even slightly out of sync. “A 4-month-old can barely hold their head up but if there’s a tape delay, they’re not as responsive and they get upset by it,” said Georgene Troseth, an associate professor of psychology and human development at Vanderbilt University. “Really tiny babies pick up on the social responsiveness of a person. If there’s something wacky about it, it bothers them.”

Study after study has demonstrated that when the natural timing in an interaction lags, it can “really hurt a baby’s ability to learn,” said Rachel Barr, a developmental psychologist at Georgetown. “So it’s an interesting question: How do we form a knowledge of people if we’re only seeing them in two dimensions? How do we know if they’re interacting with us?"

Babies end up learning best, perhaps not surprisingly, with guidance from a trusted caregiver. So despite the ream of technological limitations that can accompany Internet-based video chats, even infants can cope well when a call doesn’t go as planned. “Just saying something like, ‘The internet’s not working,’” Barr said. “That’s what you would do if you were orienting a child to any other sort of new play situation, helping them navigate. Trying to figure out what’s in the world and who's in the world—this can be done in creative ways across a screen. And kids are responding in ways as if the screen was not there.”

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A growing body of research shows that babies appear to thrive on real-time video interactions. Researchers have found that toddlers are more comforted by their mothers via video chat than they are through audio alone. And video chat appears to be, conceptually, much easier for babies to grasp than a phone conversation.

“It turns out that babies are really bad with phones,” Barr said. “Because they can’t really talk and so there’s no back-and-forth ... The baby may be nodding and communicating, but there’s no way for the person on the other end to see that they’re responding. And there’s no way for the baby to know the person can’t see them.”

These sorts of challenges in logic and reasoning exist not just for babies but for older kids, too, all the way up to around the time a child is in second grade. “Previous observational research has shown that children under 7 have trouble using phones—and babies and toddlers in particular have trouble with it,” McClure said. “They're pre-verbal. There are a lot of cognitive skills that go into understanding what a disembodied voice represents.”

More broadly, watching how babies handle interactions that are separated by a screen is one way to get at the question of how they process and understand their surroundings in general. “What they understand as being reality, whether they know a grandparent is a grandparent,” McClure said. “There are a few things that came up as we were observing that have really made me start asking: How are babies perceiving reality?” That’s a question that Troseth, the psychologist at Vanderbilt, has been focused on since long before video chats existed. More than a decade ago, she and her research team would rig up a camcorder and a screen so they could assess how babies might react to seeing themselves on a monitor in real-time—an experience that’s now common with smartphones that have forward-facing cameras. But the ability to look at a screen and discern what’s real, or what’s happening in real-time, has implications that extend beyond any specific technological application. “How does a picture represent reality? This is the very beginning of symbolic reality, a kid's exposure to a moving picture, so that’s very important,” she said.

Troseth and her colleagues have data that shows children, by 2 years old, are able to figure out that what they see on television is not real because it's not directly connected to their environment. Of course, that depends on how much exposure to television a child has had. Which brings us back to the growing population of babies who get limited exposure to TV, but frequently participate in video chats.

“If you had a kid who had never seen television and they’d never used a computer—and the first time they used a screen there’s a person using their name and talking to them—what would their experience be like compared with someone whose experience with screens first involved roadrunners running off a cliff and not falling down?” Troseth said. “I think the social support of the person who’s with the child could be really, really important.”

That’s exactly what other researchers have found. In addition to helping babies understand what’s going on when a video chat is frozen or otherwise malfunctioning, McClure says she observed lots of interactive play between babies on one side of a video chat and the adults on the other—with help from the caregivers sitting next to the babies. Many of them would play little games that helped establish the video chat as an interaction, rather than a one-way broadcast. Imagine, for instance, a grandfather blowing in the direction of the screen, and the parent sitting next to the child on the other side of that screen blowing onto her face so she can feel the effect. “Babies also like to share things through the screen, particularly food,” McClure told me. “They like to try to feed their grandparents. Then [the grandparents] pretend to receive the food on the side and eat it.”

These interactions may seem silly, but their implications are profound. McClure recalls one toddler who was trying to feed raisins to her grandfather through the screen of the iPad on which he appeared. The little girl would walk around the iPad with a handful of raisins and look for him. She’d also leave raisins for him there, behind the screen. Her mother tried to help her understand that although the man appeared on the screen, he actually lived in another house some distance away. “The mother kept saying, ‘Where does Grandpa live?’ And the little girl pointed to the screen and said, ‘Right there!’ And in a sense, that is where he lives. When you want to see Grandpa, you go to the screen and ask for him.”

Children are able, eventually, to grasp the fact that a conversation with a person who appears onscreen does not mean that person is inside the device on which he appears. But how important is that distinction in the early stages of a baby’s life, anyway? Much of what babies first learn about human interaction, with or without technology, involves metaphor and simulation. For the babies who spend time video-chatting, it emerges not just in pretending to feed somebody raisins through an iPad, but through gestures of affection.

“We saw a lot of screen kisses that, to me, really raise a question about what’s real,” McClure told me. “In one sense, it’s impossible for them to touch. But, on the other hand, affection really is being transferred. It’s kind of like blowing a kiss. Everyone knows that a kiss can’t fly through the air, but it’s a socially accepted form of affection. It’s something we teach babies to do really early on.”

Researchers believe that something similar may be happening in the way babies learn about human relationships through screen-based communication. Video chatting may be redefining the fundamental basis on which babies form an understanding of social interactions. “Parents are not encouraging a child to pretend to give affection," McClure said. “They’re encouraging them to give real affection through the screen. They don’t say, ‘Kiss the screen.’ They say, ‘Kiss Grandma.’ They are teaching them that it is real.”