Visitors to Johns Hopkins Laboratory for Child Development could easily confuse it with a preschool classroom. In the brightly lit waiting room, windows shaped like triangles and circles, in addi- tion to the more traditional square, occupy one wall. Toys of every kind take up ample floor space. And on most days, children roam the room, from the train table to the bead mazes, always in perpetual motion.

But rather than being a spot where children learn, it’s really a place where the adults try to learn a thing or two from the children, says Lisa Feigenson, an associate professor in the Department of Psychological and Brain Sciences. She and her colleagues are using these young subjects to answer a question that thinkers have pondered for thousands of years: How much knowledge do we come into the world with, and how do our experiences change that knowledge as we grow up?

“In order to understand what we learn, and how, we really need to know what we start with in the first place before learning occurs, so we can get a grasp on how that gets built upon as we gather experience with the world,” says Feigenson.

Most of Feigenson’s subjects are quite young—toddlers, infants, and even newborns just a few hours old. The challenge, and often the fun, of trying to figure out what this age group knows is that unlike most psychology research volunteers, babies can’t talk. Consequently, she and her colleagues have to carefully design experiments to capitalize on what babies can do to convey what’s going on inside their mysterious brains.

One thing that babies excel at, Feigenson says, is gazing. It’s no secret to any parent that babies tend to look at anything interesting or surprising, even when they’re just fresh out of the womb. For decades, developmental psychologists have been taking advantage of this phenomenon to gauge what babies already know (the boring things that merit just a cursory glance before the young subjects look away) and distinguish it from what’s new to them (the unusual things that need a closer look).

Using these “looking time” tests, Feigenson and her colleagues have discovered a slew of interesting facts about what babies know about how the world works, and when they gain that knowledge.

Take the idea of “object permanence,” the concept that objects still exist even when they are out of sight. Researchers long thought this ability emerges around 6 months of age. But using an experiment in which babies sit in front of a miniature puppet stage and watch as objects placed under a blanket either remain there once it’s lifted or disappear through a sleight of hand, Feigenson and colleagues have discovered that object permanence manifests much earlier, as soon as 2 months of age.

They’ve also learned that babies around 2 months of age can understand the elementary physics concept that a solid object can’t pass through a wall. Using the puppet stage again, the researchers found that babies look significantly longer when a ball rolling down a hill seemingly passes through a solid wall compared with the “boring” scenario of it stopping.

Feigenson notes that her work doesn’t stop at finding out what babies know—she’s building on those discoveries to figure out how babies learn. “We’re not equal opportunity learners,” she explains. “We pay more attention to some things than others.”

For example, if a ball really did have the amazing power to move through walls, wouldn’t you want to find out more about it? Knowing that infants are surprised when their concept about how the world works doesn’t fit with what they’re seeing, the researchers recently examined whether infants between 9 and 12 months were more likely to learn something new about that mysterious ball when it defied their expectations. After the ball seemingly rolled through a wall, or stopped as babies might expect, the experimenters shook it, making a jingling sound. Then they showed babies the ball and a different object (a toy car) and made the jingling sound from between the two objects. Babies looked at the ball, indicating that they learned something about the object (it jingles), rather than simply showing a preference to look at things that behaved unexpectedly in the past.

As anyone who’s worked with children can attest, there’s always so much more to learn about these tiny beings—work that will keep Feigenson and her colleagues busy for years to come. “We’ve really only scratched the surface with this basic research,” she says.