David Uttal's recent work takes a serious look at a funny phenomenon: toddlers' misperception of scale. For a study he coauthored, published in Science last year, the children first played with a child-size chair, slide, and car, then were taken for a walk and brought back to the same room, which this time contained a tiny chair, tiny slide, and tiny car. Several of them tried to get on or in the miniatures just as they had the child-size ones.
Harold Henderson: What made you see this as something worth looking into?
David Uttal: Judy DeLoache, a coauthor of the study based at the University of Virginia, was my postdoctoral mentor at the University of Illinois, and we've talked about cognitive development for years. It turns out that studying children's understanding of scale models is an excellent way to look at a general question: How do children come to understand symbolic relations, that one thing can stand for another? This basic ability is almost a defining characteristic of what it means to be human. We rely on symbolic skills whenever we read, look at a map, solve a mathematical problem, or read music. In each of these situations we must understand that what's on the page or in the model stands for something else.
We asked children to use scale models to find hidden toys in the room. By the age of three, most children could do so. However, we also noticed something that initially struck us as odd. Every once in a while a child would try to sit in the miniature scale model. Then we heard other researchers and parents report seeing similar errors. When I saw my 18-month-old daughter try to lie down in a doll's bed, we became convinced that there was something very important about these errors--they weren't just cute but also a way to study the developing mind and brain.
HH: Are you sure the kids weren't just playing pretend?
DU: If you check out the videos (at www.faculty.Virginia.edu/chilstudycenter/projects.html) you'll see that they're really trying to sit on the chair or get into the tiny car. One girl even takes off her shoes and socks in an effort to get her foot in the tiny car window. Judy did a follow-up study in which the children were encouraged to pretend play with the little car, and they did quite different things like pushing it around and making car noises, not trying to get into it.
HH: Maybe they just don't know how big their bodies really are.
DU: Actually, we've done work on scale errors using dolls and doll-size chairs as well. Toddlers will make these same errors when the dolls are supplied with chairs that are far too small for the dolls. So it's not simply that they've misjudged the size of their own bodies.
HH: What makes this worth studying, though? Kids do funny things as they learn about the world--they have to try things out.
DU: Well, this kind of scale error is a bit mysterious. Much younger children, even infants, can discriminate the size of objects, so why would older children sometimes ignore the fact that these objects are so small?
HH: I see. They've already learned about size, so what's going on here?
DU: There's been a lot of research with adults suggesting that two different brain systems, located in different places in the brain, are at work here. One system recognizes objects and plans what to do with them--"I'm going to sit down in that chair." The other system perceives size and implements the plan. If the two systems aren't coordinated, a person might decide to sit in a chair without bringing to bear his or her knowledge of how small it is. In healthy adults these two systems work together seamlessly in an intricate, well-controlled way. But once in a while that control breaks down, and this is more likely to happen in young children than in adults. So these errors actually tell us more about children's brains than "correct" behavior does.
HH: Who funds your work?
DU: Judy's grant is from the National Institute of Child Health and Human Development. We also have a joint grant from the U.S. Department of Education to research children's understanding of symbols. We're looking at what activities influence children's going from treating letters as objects to treating them as representations. We're wondering whether having those magnetic plastic letters on refrigerator doors speeds or slows that transition--it might make kids think of them more as objects than as symbols.
HH: What's next on scale errors?
DU: We want to know exactly what causes them. For example, we know that children make scale errors only occasionally. Most of the time they treat miniature and large chairs differently. What sorts of things precede scale errors?
In our study we had children play with the large objects before we introduced the miniature objects. We don't know whether this happens in the real world. Are scale errors more likely to happen right after the child has played with the regular-size object? Or can other activities also lead to the errors? For example, what would happen if we read some children a story about a chair and other children a different story? Will the ones who heard about the chair be more likely to try to sit in the tiny chairs?
If they do, then that shows that scale errors can happen at a higher mental level than just repeating a motor action--and we'll be one step closer to learning how children learn to control their own thinking.
Art accompanying story in printed newspaper (not available in this archive): photo/Jim Newberry.