Steven Pinker -- How the Mind Works - Hampshire High Italian ...

Good Ideas | 317of persisting objects that follow mechanical laws. We should expectinfants to show some appreciation of physics from the start.Only careful laboratory studies can tell us what it is like—rather,what it was like—to be a baby. Unfortunately, infants are difficult experimentalsubjects, worse than rats and sophomores. They can't easily beconditioned, and they don't talk. But an ingenious technique, refined bythe psychologists Elizabeth Spelke and Renee Baillargeon, capitalizes onone feat that infants are good at: getting bored. When infants see thesame old thing again and again, they signal their boredom by lookingaway. If a new thing appears, they perk up and stare. Now, "old thing"and "new thing" are in the mind of the beholder. By seeing what revivesbabies' interest and what prolongs their ennui, we can guess at whatthings they see as the same and what things they see as different—thatis, how they categorize experience. It's especially informative when ascreen first blocks part of the infant's view and then falls away, for wecan try to tell what the babies were thinking about the invisible part oftheir world. If the baby's eyes are only momentarily attracted and thenwander off, we can infer that the scene was in the baby's mind's eye allalong. If the baby stares longer, we can infer that the scene came as asurprise.Three- to four-month-old infants are usually the youngest tested, bothbecause they are better behaved than younger babies and because theirstereo vision, motion perception, visual attention, and acuity have justmatured. The tests cannot, by themselves, establish what is and is notinnate. Three-month-olds were not born yesterday, so anything theyknow they could, in theory, have learned. And three-month-olds stillhave a lot of maturing to do, so anything they come to know later couldemerge without learning, just as teeth and pubic hair do. But by tellingus what babies know at what age, the findings narrow the options.Spelke and Philip Kelman wanted to see what infants treated as anobject. Remember from Chapter 4 that it is not easy, even for an adult, tosay what an "object" is. An object can be defined as a stretch of the visualfield with a smooth silhouette, a stretch with a homogeneous color andtexture, or a collection of patches with a common motion. Often thesedefinitions pick out the same pieces, but when they don't, it is commonmotion that wins the day. When pieces move together, we see them as asingle object; when pieces go their separate ways, we see them as separateobjects. The concept of an object is useful because bits of matterthat are attached to one another usually move together. Bicycles and