This is an article from the spring 2015 issue of LSA Magazine. Read more stories from the magazine.

For a long time, psychologists assumed that babies and young children thought about the world in a superficial way. But former Interim Dean Susan Gelman’s pioneering research has opened up an entirely new understanding of how sophisticated children’s thoughts really are.

Until about 30 years ago, people believed that infants and toddlers lived in a permanent present where they only thought about the things right in front of them—this spoonful of applesauce, that stuffed animal.

Influential developmental psychologist Jean Piaget’s experiments about object permanence suggested that once you removed an object from a baby’s view, the baby would forget about it. This idea became fundamental to the way we thought about babies and how their minds work. Based on this and many other experiments he conducted over more than 50 years, Piaget neatly laid out stages of cognitive growth that became a central tenet of developmental psychology.

It turns out, says Susan Gelman, Heinz Werner Distinguished University Professor of Psychology, we were wrong about a lot of it.

“This puts it too crudely, but it used to be thought that babies in particular and even young children didn’t know anything,” says Gelman. “Now we marvel at the depth and sophistication of all that they know.”

The How and the Why

Piaget’s research set the stage for many important discoveries in developmental psychology in the almost 80 years since he began his work in 1936. Piaget was brilliant at observing children and noticing real changes that were taking place in their approach to the world, Gelman says, but he misunderstood the reasons why those changes were taking place. He greatly underestimated what children bring to the task of learning, and he greatly underestimated the importance of social interactions.

“Children live in a social and cultural context,” says Gelman, “and social interactions—including language—deeply influence what they think.”

Gelman’s research confirms that kids seem to think with many of the same patterns, structures, and cognitive biases as adults—including a fundamental bias psychologists describe as “essentialism.”

In Gelman's family-friendly Conceptual Development Lab, researchers conduct experiments in a home-like setting that puts kids and parents at ease.

Essentialism, explains Gelman, is the way we think about many everyday categories, such as cats or elephants. It’s the idea that these categories have an underlying reality that we can’t directly see. Cats not only have four legs and pointy ears, but they also have an inborn, invisible “cat essence.”

In one study, preschoolers said that a crow would feed its baby the same food as a flamingo, not a bat, because the crow and the flamingo are both birds—even though the crow and bat looked more alike. In another study where researchers told 4-year-olds about a baby kangaroo that was raised by goats, children said that the kangaroo would still have a pouch and be better at hopping than climbing. Yet another study found that children expected an animal’s internal parts to determine its identity even more than the way it looked.

Gelman finds such experiments compelling because they illuminate that children expect the world to have a hidden structure. This expectation has far-reaching implications for how children think about social categories, such as gender, ethnicity, or race because it means the children treat some social categories as if they are as fixed and inflexible as biological categories.

“It turns out that young children are essentialist about some of these social categories from a very early age, but not universally,” Gelman says. “Figuring out when and why they do so is very important for understanding issues related to stereotype and intergroup conflict.”

Such awareness shows that small children are not simply passive collectors; they are actively analyzing the information they’re absorbing from the world, and they’re doing so at a very early age.

“I think the findings from essentialism show that children are searching to understand the causes of things,” says Gelman. “They’re trying to understand invisible properties and hidden features, and these things are very central to how they view the world.”

The Roots of Ideas

In her Conceptual Development Lab on campus, Gelman and her team of researchers have conducted myriad experiments related to essentialism that have helped to map out additional details about the way young children think.

Some of the experiments in Gelman's lab use made-up words like “ziblet” and “flurp” to test kids' ability to generalize their perceptions from one category of objects to another.

Gelman’s research confirms a number of things: Very young children have a definite grasp of cause and effect. They understand that human processes—like building a table—are distinct from biological ones—like a puppy growing into an adult dog. They are also savvy about extremely subtle cues in language. “Even 2-year-olds distinguish Lily as a proper name from lily as a common noun,” Gelman says.

These insights are drawn from experiments conducted at different points in Gelman’s long and distinguished career, and studying the mix of essentialist tendencies, environmental conditions, and social categories that shape children’s thinking continues to captivate her. “This is something,” Gelman says, “I’ve been interested in forever.

“I think very few scientists study kids just because they’re cute and charming, although they certainly are,” she says. “But by studying small children, you can also get a clear look at the origins of concepts before they’ve been altered by education and social desirability. You can really see which ideas require intensive instruction and which are really basic and core to being a human being.”

Perhaps the lasting outcomes of Gelman’s research will not only be a deeper understanding of the richly textured world that small children experience, but a better understanding of how big people’s minds work, too.