On
the way to learning that one thing can represent another, young children often
conflate the real item and its symbol. These errors show how difficult it is to
start thinking symbolically
By
Judy S. DeLoache
Scientific
American, July 25, 2005
About
20 years ago I had one of those wonderful moments when research takes an
unexpected but fruitful turn. I had been studying toddler memory and was
beginning a new experiment with two-and-a-half- and three-year-olds. For the
project, I had built a model of a room that was part of my lab. The real space
was furnished like a standard living room, albeit a rather shabby one, with an
upholstered couch, an armchair, a cabinet and so on. The miniature items were
as similar as possible to their larger counterparts: they were the same shape
and material, covered with the same fabric and arranged in the same positions.
For the study, a child watched as we hid a miniature toy--a plastic dog we
dubbed "Little Snoopy"--in the model, which we referred to as
"Little Snoopy's room." We then encouraged the child to find
"Big Snoopy," a large version of the toy "hiding in the same
place in his big room." We wondered whether children could use their
memory of the small room to figure out where to find the toy in the large one.
The
three-year-olds were, as we had expected, very successful. After they observed
the small toy being placed behind the miniature couch, they ran into the room
and found the large toy behind the real couch. But the two-and-a-half-year-olds,
much to my and their parents' surprise, failed abysmally. They cheerfully ran
into the room to retrieve the large toy, but most of them had no idea where to
look, even though they remembered where the tiny toy was hidden in the
miniature room and could readily find it there.
Their
failure to use what they knew about the model to draw an inference about the
room indicated that they did not appreciate the relation between the model and
room. I soon realized that my memory study was instead a study of symbolic
understanding and that the younger children's failure might be telling us
something interesting about how and when youngsters acquire the ability to
understand that one object can stand for another.
What
most distinguishes humans from other creatures is our ability to create and
manipulate a wide variety of symbolic representations. This capacity enables us
to transmit information from one generation to another, making culture
possible, and to learn vast amounts without having direct experience--we all
know about dinosaurs despite never having met one. Because of the fundamental
role of symbolization in almost everything we do, perhaps no aspect of human
development is more important than becoming symbol-minded. What could be more
fascinating, I concluded, than finding out how young children begin to use and
understand symbolic objects and how they come to master some of the symbolic
items ubiquitous in modern life. As a result of that fortuitous model-room
experiment, I shifted my focus from memory to symbolic thinking.
Pictures
Come to Life
The
first type of symbolic object infants and young children master is pictures. No
symbols seem simpler to adults, but my colleagues and I have discovered that
infants initially find pictures perplexing. The problem stems from the duality
inherent in all symbolic objects: they are real in and of themselves and, at
the same time, representations of something else. To understand them, the
viewer must achieve dual representation: he or she must mentally represent the
object as well as the relation between it and what it stands for.
A
few years ago I became intrigued by anecdotes suggesting that infants do not
appreciate the dual nature of pictures. Every now and then, I would hear of a
baby who tried to pick up a depicted apple or to fit a foot into a photograph
of a shoe. My colleagues--David H. Uttal of Northwestern University, Sophia L.
Pierroutsakos of St. Louis Community College and Karl S. Rosengren of the
University of Illinois at Urbana-Champaign--and I decided to investigate even
though we assumed such behaviors would be rare and therefore difficult to
study. Fortunately, we were wrong.
We
began testing infants' understanding of pictures in a very simple way. We put a
book containing highly realistic color photographs of individual objects in
front of nine-month-olds. To our surprise, every child in the initial study,
and most in our subsequent studies, reached out to feel, rub, pat or scratch
the pictures. Sometimes the infants even grasped at the depicted objects as if
trying to pick them up off the page.
We
had a unique opportunity to see how universal this response was when
anthropologist Alma Gottlieb of the University of Illinois took some of our
books and a video camera to a remote Beng village in Ivory Coast. The testing
situation there was different: Beng babies sat on the ground or in their
mother's lap as chickens and goats wandered around and other children and
villagers played, worked, talked and laughed nearby. Yet the Beng babies, who
had almost certainly never seen a picture before, manually explored the
depicted objects just as the American babies had.
The
confusion seems to be conceptual, not perceptual. Infants can perfectly well
perceive the difference between objects and pictures. Given a choice between
the two, infants choose the real thing. But they do not yet fully understand
what pictures are and how they differ from the things depicted (the
"referents") and so they explore: some actually lean over and put
their lips on the nipple in a photograph of a bottle, for instance. They only
do so, however, when the depicted object is highly similar to the object it
represents, as in color photographs. The same confusion occurs for video
images. Pierroutsakos and her colleague Georgene L. Troseth of Vanderbilt
University found that nine-month-olds seated near a television monitor will
reach out and grab at objects moving across the screen. But when depicted
objects bear relatively little resemblance to the real thing--as in a line
drawing--infants rarely explore them.
By
18 months, babies have come to appreciate that a picture merely represents a
real thing. Instead of manipulating the paper, they point to pictures and name
objects or ask someone else for the name. Melissa A. Preissler of Yale
University and Susan Carey of Harvard University recently provided a good
example of this development. The two researchers used a simple line drawing of
a whisk to teach 18- and 24-month-olds the word for this object that they had
not seen before. Most of the children assumed the word referred to the object
itself, not just to the picture of it. In other words, they interpreted the
picture symbolically--as standing for, not just being similar to, its referent.
One
factor we think contributes to the decline of manual exploration of pictures is
the development of inhibitory control. Throughout the first years of life,
children become increasingly capable of curbing impulses. This general
developmental change is supported by changes in the frontal cortex. Increased
inhibitory control presumably helps infants restrain their impulse to interact
directly with pictures, setting the stage for them to simply look, as adults
do.
Experience
with pictures must play a role in this development as well. In an image-rich
society, most children encounter family photographs and picture books on a
daily basis. Such interactions teach children how pictures differ from objects
and how they are supposed to be targets of contemplation and conversation, not
action.
Nevertheless,
it takes several years for the nature of pictures to be completely understood.
John H. Flavell of Stanford University and his colleagues have found, for
example, that until the age of four, many children think that turning a picture
of a bowl of popcorn upside down will result in the depicted popcorn falling
out of the bowl.
Pictures
are not the only source of symbol confusion for very young children. For many
years, my colleagues and students and I watched toddlers come into the lab and
try to sit down on the tiny chair from the scale model--much to the
astonishment of all present. At home, Uttal and Rosengren had also observed
their own daughters trying to lie down in a doll's bed or get into a miniature
toy car. Intrigued by these remarkable behaviors that were not mentioned in any
of the scientific literature we examined, we decided to study them.
Gulliver's
Errors
We
brought 18- to 30-month-old children into a room that contained, among other
things, three large play objects: an indoor slide, a child-size chair and a car
toddlers could get inside and propel around the room with their feet. After a
child had played with each of the objects at least twice, he or she was
escorted from the room. We then replaced the large items with identical
miniature versions. When the child returned, we did not comment on the switch
and let him or her play spontaneously. If the toddler ignored the miniature
toys for more than three or four minutes, however, we would draw attention to
them.
We
then examined films of the children's behavior for what we came to call scale
errors: earnest attempts to perform actions that are clearly impossible because
of extreme differences in the relative size of the child's body and the target
object. We were very conservative in what we counted as a scale error.
Almost
half the children committed one or more of these mistakes. They attempted with
apparent seriousness to perform the same actions with the miniature items that
they had with the large ones. Some sat down on the little chair: they walked up
to it, turned around, bent their knees and lowered themselves onto it. Some
simply perched on top, others sat down so hard that the chair skittered out
from under them. Some children sat on the miniature slide and tried to ride
down it, usually falling off in the process; others attempted to climb the
steps, causing the slide to tip over. (With the chair and slide made of sturdy
plastic and only about five inches tall, the toddlers faced no danger of
hurting themselves.) A few kids tried to get into the tiny car. Just as they
had done with the large version, they opened the door and attempted--often with
remarkable persistence--to force a foot inside. One little girl went so far as
to take off her shoe in the apparent hope that her foot would then fit!
Interestingly,
most of the children showed little or no reaction to their failed attempts with
the miniatures. A couple seemed a bit angry, a few looked sheepish, but most
simply went on to do something else. We think the lack of reaction probably
reflects the fact that toddlers' daily lives are full of unsuccessful attempts
to do one thing or another.
Our
interpretation is that scale errors originate in a dissociation between the use
of visual information for planning an action and for controlling its execution.
When a child sees a miniature of a familiar object, visual information--the
object's shape, color, texture and so on--activates the child's mental
representation of its referent. Associated with that memory is the motor
program for interacting with the large object and other similar objects. In
half the children we studied, this motor program was presumably activated but
then inhibited, and the children did not attempt to interact with the miniature
in the same way as they did with the large version.
But
in the other half the motor routine was not inhibited. Once the child began to
carry out the typical motor sequence, visual information about the actual size
of the object was used to accurately perform the actions. Some children, for instance,
bent over the tiny chair and looked between their legs to precisely locate it;
those trying to get into the miniature car first opened its door and then tried
to shove their foot right in. In deciding to interact with the replica, the
children relied on visual information linking it to the normal-size object, but
in executing their plan, they used visual information about the miniature's
actual size to guide their actions. This dissociation in the use of visual
information is consistent with influential theories of visual processing--ones
positing that different regions of the brain handle object recognition and
planning versus the execution and control of actions.
Scale
errors involve a failure of dual representation: children cannot maintain the distinction
between a symbol and its referent. We know this because the confusion between
referent and symbolic object does not happen when the demand for dual
representation is eliminated--a discovery I made in 1997 when Rosengren and
Kevin F. Miller of the University of Illinois and I convinced
two-and-a-half-year-olds--with the full consent of their parents, of
course--that we had a device that could miniaturize everyday objects.
The
Magical Machine
Using
our amazing shrinking machine, we hoped to see if the need to think of an
object in two ways at once was at the heart of young children's inability to
appreciate symbols. If a child believes that a machine has shrunk an object or
a room, then in the child's mind the miniature is the thing itself. There is no
symbolic relation between room and model, so children should be able to apply
what they know about the big version to the little one.
We
used the powers of our device to turn toys into miniature versions of
themselves and to shrink a large tent. In front of the child, we placed a
toy--a troll doll with vivid purple hair--in a tent and aimed the shrinking
machine at the tent. The child and experimenter then decamped to another room
to wait while the machine did its work. When they returned to the lab, a small
tent sat where the big one had been. (One of the remarkable things about this
study is the fact that the children did not find it at all surprising that a
machine could miniaturize objects. Or that it might need privacy to do so.)
When
we asked the children to search for the toy, they immediately looked in the
small tent. Believing the miniature to actually be the original tent after
shrinking, they successfully retrieved the hidden toy. Unlike in our scale
model experiment, they had no dual representation to master: the small tent was
the same as the large tent, and thus the toy was where it should be, according
to the toddlers' view of the world.
Understanding
the role of dual representation in how young children use symbols has important
practical applications. One has to do with the practice of using dolls to
interview young children in cases of suspected sexual abuse. The victims of
abuse are often very young children, who are quite difficult to interview.
Consequently, many professionals--including police officers, social workers and
mental health professionals--employ anatomically detailed dolls, assuming that
a young child will have an easier time describing what happened using a doll.
Notice that this assumption entails the further assumption that a young child
will be able to think of this object as both a doll and a representation of
himself or herself.
These
assumptions have been called into question by Maggie Bruck of Johns Hopkins
University, Stephen J. Ceci of Cornell University, Peter A. Ornstein of the
University of North Carolina at Chapel Hill and their many colleagues. In
several independent studies, these investigators have asked preschool children
to report what they remember about a checkup with their pediatrician, which
either had or had not included a genital check. Anatomically detailed dolls
were sometimes used to question the children, sometimes not. In general, the
children's reports were more accurate when they were questioned without a doll,
and they were more likely to falsely report genital touching when a doll was
used.
Based
on my research documenting young children's difficulty interpreting symbolic
objects, I suspected that very young children might not be able to relate their
own body to a doll. In a series of studies in my lab using an extremely simple
mapping task, Catherine Smith placed a sticker somewhere on a child--on a
shoulder or foot, for example--and asked the child to place a smaller version
of the sticker in the same place on a doll. Children between three and
three-and-a-half usually placed the sticker correctly, but children younger
than three were correct less than half the time. The fact that these very young
children cannot relate their own body to the doll's in this extremely simple
situation with no memory demands and no emotional involvement supports the
general case against the use of anatomically detailed dolls in forensic
situations with young children. (Because of many demonstrations akin to this
one, the use of dolls with children younger than five is viewed less favorably
than in the past and has been outlawed in at least one state.)
Educational
Ramifications
The
concept of dual representation has implications for educational practices as
well. Teachers in preschool and elementary school classrooms around the world
use "manipulatives"--blocks, rods and other objects designed to
represent numerical quantity. The idea is that these concrete objects help
children appreciate abstract mathematical principles. But if children do not
understand the relation between the objects and what they represent, the use of
manipulatives could be counterproductive. And some research does suggest that
children often have problems understanding and using manipulatives.
Meredith
Amaya of Northwestern University, Uttal and I are now testing the effect of
experience with symbolic objects on young children's learning about letters and
numbers. Using blocks designed to help teach math to young children, we taught
six- and seven-year-olds to do subtraction problems that require borrowing (a
form of problem that often gives young children difficulty). We taught a
comparison group to do the same but using pencil and paper. Both groups learned
to solve the problems equally well--but the group using the blocks took three
times as long to do so. A girl who used the blocks offered us some advice after
the study: "Have you ever thought of teaching kids to do these with paper
and pencil? It's a lot easier."
Dual
representation also comes into play in many books for young children. A very
popular style of book contains a variety of manipulative features designed to
encourage children to interact directly with the book itself--flaps that can be
lifted to reveal pictures, levers that can be pulled to animate images, and so
forth.
Graduate
student Cynthia Chiong and I reasoned that these manipulative features might
distract children from information presented in the book. Accordingly, we
recently used different types of books to teach letters to 30-month-old
children. One was a simple, old-fashioned alphabet book, with each letter
clearly printed in simple black type accompanied by an appropriate picture--the
traditional "A is for apple, B is for boy" type of book. Another book
had a variety of manipulative features. The children who had been taught with
the plain book subsequently recognized more letters than did those taught with
the more complicated book. Presumably, the children could more readily focus
their attention with the plain 2-D book, whereas with the other one their attention
was drawn to the 3-D activities. Less may be more when it comes to educational
books for young children.
As
these various studies show, infants and young children are confused by many
aspects of symbols that seem intuitively obvious to adults. They have to
overcome hurdles on the way to achieving a mature conception of what symbols
represent, and today many must master an ever expanding variety of symbols.
Perhaps a deeper understanding of the various stages of becoming symbol-minded
will enable researchers to identify and address learning problems that might
stem from difficulty grasping the meanings of symbols.
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