If you had been blind all your life and could suddenly see, could you distinguish by sight what you knew already by touch--say, a cube from a sphere? Would flowers look like flowers you'd felt and faces like faces, or would they all be confusing patterns? How would you start to make sense of the many objects in your immediate view? If we are born knowing nothing, how do we come to know anything?
Harvard University psychologist Elizabeth Spelke takes these questions to the people who may be best able to answer them: babies. Spelke, whose sprawling laboratory in William James Hall teems with infants and researchers who are interested in them, has addressed some of the most intractable mysteries of human knowledge by interrogating little people who cannot yet talk, walk or even crawl. She has what she calls "an insatiable appetite" for assessing these young beings. Through Web pages, flyers and letters to day care centers and pediatricians' offices, her lab mates ask anyone and everyone for diminutive volunteers. They watch as the little subjects sit on their mothers' laps, tracking the stagecraft that Spelke and her cohorts use to gauge early understanding of numbers, language, objects, space and movement.
Spelke's findings have helped revise sharply our notion of what humans can make sense of in their first days, weeks and months. In doing so, she has offered some of the most substantial evidence to date regarding nature versus nurture. Spelke's discoveries about infant capabilities have become central to ongoing attempts to figure out human cognition.
From her insights she has forged a bold, if still controversial, theory of "core knowledge," which asserts that all humans are born with basic cognitive skills that let them make sense of the world. This core knowledge, she says, underlies everything we learn throughout our lives and both unifies and distinguishes us as a species. Her theory prompted the American Psychological Association to honor her with its William James Fellow Award in 2000. And her work shows that, despite people's differences, we all have more in common than we recognize.
Clarity, Not Confusion
The heart of Spelke's methodology is her observation of "preferential looking"--the tendency of infants and children to peer longer at something that is new, surprising or different. Show a baby a toy bunny again and again, and the baby will give it a shorter gaze each time. But give the bunny four ears on, say, its tenth appearance, and if the baby looks longer, you know the baby can discern four from two. The approach neatly bypasses infants' deficiencies in speech or directed movement and makes the most of the one thing they control well: how much time they fix their eyes on an object.
Spelke did not invent the scheme of studying preferential looking. That credit falls to Robert L. Fantz, a Western Reserve University psychologist who in the 1950s and early 1960s discovered that chimps and infants stare longer at things they perceive as unexpected. A researcher could gauge an infant's discriminatory and perceptual powers by showing the baby different, highly controlled scenarios, usually within a stagelike box, and observing what changes in the scenarios the infant would perceive as novel.
Using this basic technique, Fantz and others soon found that the infant's world was not, as pioneering psychologist William James had opined in 1890, a "blooming, buzzing confusion." Infants made sense of the world readily. For example, Fantz and others found that newborns could differentiate red from green, two-month-olds could discriminate all primary colors, and three-month-olds preferred yellow and red to blue and green. They found that a newborn could distinguish between her mother's face and a stranger's (unless both adults wore scarves over their hair), a four-month-old could recognize acquaintances, and a six-month-old could interpret facial expressions. By the 1970s psychologists recognized the first year of life as a far more explosive developmental period than they had ever considered it to be.