Some things we know, but we don’t know how we know them. Consider your absorption of language. If you are an average secondary school graduate you know some 80,000 words (likely an underestimate given that you’re reading this book). That averages (from age 1 to 18) nearly 5,000 words learned each year, or 13 each day! How you did it— how the 5,000 words a year you learned could outnumber by so much the roughly 200 words a year that your schoolteachers consciously taught you—is one of the great human wonders. Before you could add 2 + 2 you were creating your own original and grammatically appropriate sentences. Your parents probably would have had trouble stating the rules of syntax. Yet while barely more than a toddler you intuitively comprehended and spoke with a facility that would shame a college student struggling to learn a foreign language or a scientist struggling to simulate natural language on a computer.
Even infants—well before they have begun thinking in words—possess striking intuitive capacities. We are born preferring sights and sounds that facilitate social responsiveness. As newborns, we turned our heads in the direction of human voices. We gazed longer at a drawing of a face-like image than at a bull’s-eye pattern, and longer at a bull’s-eye pattern (which has contrasts much like those of the human eye) than at a solid disk. We preferred to look at objects eight to twelve inches away, which, wonder of wonders, just happens to be the approximate distance between a nursing infant’s eyes and its mother’s.
Our perceptual abilities develop continuously during the first months of life. Within days of birth, our brain’s neural networks were stamped with the smell of our mother’s body. Thus, a week-old nursing baby, placed between a gauze pad from its mother’s bra and one from another nursing mother, will usually turn toward its own mother’s pad. A three-week-old infant, if given a pacifier that turns on recordings of either its mother’s voice or a female stranger’s, will suck more vigorously when it hears its now-familiar mother.
Babies also have an intuitive grasp of simple laws of physics. Like adults staring in disbelief at a magic trick, infants look longer at a scene of a ball stopping in midair, a car seeming to pass through a solid object, or an object that seems to disappear. Babies even have a head for numbers. Researcher Karen Wynn showed five-month-old infants one or two objects. Then she hid the objects behind a screen, sometimes removing or adding one through a trap door. When she lifted the screen, the infants often did a double take, staring longer when shown a wrong number of objects. Like animals’ native fear of heights, this is intuitive knowledge—unmediated by words or rational analysis.
