THE BABY LAB.(work of Elizabeth Spelke, a cognitive psychologist)

On weekday mornings at nine o'clock, at Harvard University's Laboratory for Developmental Studies, the babies start arriving in a long procession, looking like young pashas in their luxurious, oversized strollers. Researchers rush out to greet them, brandishing toys and consent forms. One day this summer, eight-month-old William was carried into a small, darkened room, where he sat on his father's lap and viewed, on a screen in front of him, rectangles and dots shrinking in size or number. He was alerted to a new picture by a silly boing noise (and a brief appearance by Clifford the Big Red Dog). William, who is blond and wide-eyed, contemplated this spectacle with the grave dignity of the preverbal. By noon, most of the lab's half-dozen study rooms were occupied. Babies listened to French and English speakers coo over toys and watched piles of sand grow and diminish; toddlers hunted after hidden Cheerios and gauged the nature of gravity and solidity.

The lab, which sprawls over three buildings on the Harvard campus, is a pleasant place, with wide windows offering an expansive view of Cambridge. The waiting area has a wooden train set, and a Gary Larsonesque cartoon that someone taped up is captioned "At the National Sippy Cup Research Center." A bulletin board in the office lists ongoing studies in a surrealistic shorthand: "Talking Blobs," "Blocks and Holes," "Wet Animals." The lab is a domain of peculiar little scenarios, all energetically and painstakingly staged for the very young in an effort to probe the black box--the mysterious machine--that is their minds. It is also the domain of Elizabeth Spelke, a fifty-seven-year-old cognitive psychologist, who supervises the work of ten graduate students, twenty undergraduate research assistants, and assorted visiting scholars and postdocs, most of whom are testing various aspects of her signature idea--namely, that babies come into the world mentally equipped with certain basic systems for ordering it. Her grad students call the lab Spelkeland.

A few weeks earlier, Spelke had watched a videotape of a researcher who was running a pilot study with a talkative, curly-haired two-year-old girl. The study, which used finger puppets, was aimed at determining what kinds of mathematical concepts a toddler might understand intuitively. Could she track the number of bunny puppets that were missing when the researcher removed them from her fingers, stowed them in a box, then lifted them out, leaving one or two inside? This little girl seemed to be doing just that--she wasn't satisfied with the number of bunnies that the researcher, Veronique Izard, had removed from the box, and she was craning her neck in search of more puppets. Like all studies in Spelke's lab, this one would be evaluated at both a high level and a humble one. "Yes!" Spelke said, punching the air. "Wow! She definitely expected another one." Izard struggled to push a recalcitrant bunny puppet onto her finger, and Spelke frowned. "We definitely need to get puppets that go on faster," she said.

Later, I talked with Spelke in her sunny corner office, which featured stray touches of whimsy--an inflatable palm tree, a windup toy brain on a crowded bookshelf. When she leans forward to make a point, her shoulders hunch; she is tall and gangly, with straight, shoulder-length hair parted in the middle, large oval glasses, and a way of speaking about her work that is at once eager and precise. "I'm fascinated by babies and little kids," she said. "But the questions that really keep me up at night are: What distinguishes us from other animals? How do we make sense of what goes on around us? What are the core notions that all of our systematic knowledge is based on?"

Over the past three decades, Spelke has created a series of ingenious studies that have given us a picture of the baby mind which is far different from the long-standing view of it as, in William James's famous formulation, a "blooming, buzzing confusion." As Spelke likes to say, there are some forms of knowledge that humans get "for free." Even at two and a half months, she argues, infants apprehend certain laws of the physical world--for example, that objects are cohesive and distinct and cannot pass through solid surfaces, and that they move along expected trajectories unless something obstructs them. Contrary to the Swiss developmental psychologist Jean Piaget--who believed that babies were born with sensory capacities but with no real knowledge, and who theorized, in 1954, that infants lacked a sense of "object permanence"--Spelke says that even newborns understand that things still exist when they can no longer see them. Babies, in her view, have a sense of other people as "goal-directed agents" who are capable of forming intentions and acting on them. And humans are endowed with a natural sense of geometry, an ability to orient themselves in space.

In 1981, Spelke, along with her colleagues Barbara Landau and Henry Gleit-man, published the results of a study in which they introduced blind, or blindfolded, toddlers into a room with objects in four locations. They had the children walk between them on a specific path, then asked them to use another path to move one object to another--putting a toy onto a chair, for example. The kids proved strikingly adept at the task. Spelke's experiment linked her to Socrates, who quizzed an uneducated Athenian slave on principles of shape, angle, and line, found him remarkably apt, and concluded that geometry was a gift of the human soul. (Descartes, too, believed that humans had an innate sense of geometry; he described an exercise in which a blind man holding two sticks in front of him could infer the point at which the sticks crossed.)

Spelke's work even suggests that babies have an ability to compare large approximate sets. In 2000, a study that she did with the psychologist Fei Xu showed that six-month-old infants can reliably distinguish between displays of eight and sixteen dots; a 2005 study revealed that they could tell the difference between sixteen and thirty-two. (The subjects ran into trouble with smaller ratios.) Babies can also do a kind of addition and subtraction, tracking small numbers of objects and reasoning about what happens when one is added or taken away.