Paul Bloom
is a professor of psychology at Yale. His new book, “How Pleasure Works”
is a professor of psychology at Yale. His new book, “How Pleasure Works”
A reason this view has persisted is that, for many years, scientists weren’t sure how to go about studying the mental life of babies. It’s a challenge to study the cognitive abilities of any creature that lacks language, but human babies present an additional difficulty, because, even compared to rats or birds, they are behaviorally limited: they can’t run mazes or peck at levers. In the 1980s, however, psychologists interested in exploring how much babies know began making use of one of the few behaviors that young babies can control: the movement of their eyes. The eyes are a window to the baby’s soul. As adults do, when babies see something that they find interesting or surprising, they tend to look at it longer than they would at something they find uninteresting or expected. And when given a choice between two things to look at, babies usually opt to look at the more pleasing thing. You can use “looking time,” then, as a rough but reliable proxy for what captures babies’ attention: what babies are surprised by or what babies like.
The studies in the 1
980s that made use of this methodology were able to discover surprising things about what babies know about the nature and workings of physical objects — a baby’s “naïve physics.” Psychologists — most notably Elizabeth Spelke and Renée Baillargeon — conducted studies that essentially involved showing babies magic tricks, events that seemed to violate some law of the universe: you remove the supports from beneath a block and it floats in midair, unsupported; an object disappears and then reappears in another location; a box is placed behind a screen, the screen falls backward into empty space. Like adults, babies tend to linger on such scenes — they look longer at them than at scenes that are identical in all regards except that they don’t violate physical laws. This suggests that babies have expectations about how objects should behave. A vast body of research now suggests that — contrary to what was taught for decades to legions of psychology undergraduates — babies think of objects largely as adults do, as connected masses that move as units, that are solid and subject to gravity and that move in continuous paths through space and time.Other studies, starting with a 1992 paper by my wife, Karen, have found that babies can do rudimentary math with objects. The demonstration is simple. Show a baby an empty stage. Raise a screen to obscure part of the stage. In view of the baby, put a Mickey Mouse doll behind the screen. Then put another Mickey Mouse doll behind the screen. Now drop the screen. Adults expect two dolls — and so do 5-month-olds: if the screen drops to reveal one or three dolls, the babies look longer, in surprise, than they do if the screen drops to reveal two.
A second wave of studies used looking-time methods to explore what babies know about the minds of others — a baby’s “naïve psychology.” Psychologists had known for a while that even the youngest of babies treat people different from inanimate objects. Babies like to look at faces; they mimic them, they smile at them. They expect engagement: if a moving object becomes still, they merely lose interest; if a person’s face becomes still, however, they become distressed.But the new studies found that babies have an actual understanding of mental life: they have some grasp of how people think and why they act as they do. The studies showed that, though babies expect inanimate objects to move as the result of push-pull interactions, they expect people to move rationally in accordance with their beliefs and desires: babies show surprise when someone takes a roundabout path to something he wants. They expect someone who reaches for an object to reach for the same object later, even if its location has changed. And well before their 2nd birthdays, babies are sharp enough to know that other people can have false beliefs. The psychologists Kristine Onishi and Renée Baillargeon have found that 15-month-olds expect that if a person sees an object in one box, and then the object is moved to another box when the person isn’t looking, the person will later reach into the box where he first saw the object, not the box where it actually is. That is, toddlers have a mental model not merely of the world but of the world as understood by someone else.
Next to The Moral Life of Babies (3)
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