A Child's Life
Volume 25 Number 2
Photo by Dexter Gormley, IMDL
Photo by Dexter Gormley, IMDL
Baby Steps and Beyond
I have big plans for my baby daughter, Valerie. Besides being a columnist for the New York Times and a celebrated visual artist, she also could discover the cure for cancer, I think. What better way to unleash her scientific aptitudes than as a test subject in a world-famous lab?
Indiana University Bloomingtons Infant Motor Development Laboratory,to be exact, where Valerie has participated in two experiments under the careful study of its director, developmental psychologist and Professor of Psychology Esther Thelen.
Established in 1985, Thelens unassuming lab is a colorful and friendly space where hundreds of babies have been studiedand where Thelen formulated what is now the dominant theoretical viewpoint for the field of infant motor development.
The Body Instructs the Brain
Thelen takes a dynamic systems approach to infant motor development. Simply put, that means she believes that all the parts of a system work together to create some actionfor example, a baby successfully grasping a toy. The limbs, the muscles, and the babys visual perception of a toy all unite to produce the reaching movement.
Before Thelens approach took hold in the field, most developmental psychologists subscribed to the neuromaturational theory of infant motor development, which holds that as the brain gets bigger and better, it instructs the body to do more complicated things. In this view, a 2-month-old baby cant successfully reach for toys because her brain is not mature enough.
Thelen turned this idea on its head.
Dynamic systems theories depart from conventional approaches because they seek to understand the overall behavior of a system not by dissecting it into parts, but by asking how and under what circumstances the parts cooperate to produce a whole pattern, she explains.
Babies learn new motor skills such as reaching and sitting, Thelen says, by problem-solving and figuring out how to do things in their environment. The body, therefore, instructs the brain.
Babies are constantly trying to figure out things like How am I going to look around? and How am I going to see that nice smiley face? I believe the behavior we see is not residing somewhere in the brain. Instead, it emerges in the movement, says Thelen.
Thelens innovative dynamic systems approach has earned her international renown. She is president of the Society for Research in Child Development, past president of the International Society for Infant Studies, and a recipient of the MERIT Award from the National Institutes of Health, which funds much of her research.
That research has been featured on television programs ranging from Scientific American Frontiers to a BBC documentary series called Horizon. In July 2002, producers from The Discovery Channel came to Thelens lab to film segments for a three-part Discovery Health series on infant development.
If you want to work with a leading light in infant motor development, you would be hard-pressed to find anyone better than Esther, says Christopher Smethurst, a post-doctoral associate who came from England to work in Thelens lab.
Thelens pioneering work is not just academic. Her theories have had a large impact on the field of pediatric physical therapy as well, which used to follow a rigid developmental sequence based on neuromaturational theory. Turning more toward the biomechanical properties of babies, the American Physical Therapy Association now runs seminars on the dynamic systems model.
Tots in the Tank
Thelens well-known fish tank experiment demonstrates her assertion that behavior emerges in movement. Newborn infants exhibit an early stepping reflex. When supported under the armpits with feet lowered to a table, a baby will take steps. This only lasts for a month or two. After that, it was thought that the reflex becomes inhibited by other parts of the brain as the baby matures.
But was it really inhibited?
Anyone whos ever been around babies knows they kicka lot. They kick when theyre happy, when theyre hungry, when theyre excited, when theyre mad. Lay a young baby down on a blanket or put her in an infant seat, and that baby will soon be flailing her little legs.Thelen noticed that all that kicking looked like stepping in a lying-down position. She wondered, How could the maturing brain exert an inhibitory influence in one posture but not in another?
Thelen considered what else was happening with the babys body. An infants constant eating and sleeping leads to some very chubby thighs. Does gravity make it hard for her to lift her legs once she starts putting on baby fat?
To test this hypothesis, Thelen put 2-month-olds in torso-deep warm water in a large fish tank. Since heavy limbs would be buoyant underwater, she waited to see if the stepping resumed.
As predicted, our wet and slippery subjects all stepped like crazy, says Thelen. Before then, no one had thought about what the nervous system was movinga pair of big, fat legs!
Thelen has experimented with treadmills, too, which also restored the lost stepping reflex. Held upright and placed on a special tabletop treadmill, babies were able to produce coordinated and alternating steps.
Is this because the brain has finally matured enough to allow the baby to walk? Not in Thelens view. According to her dynamic systems theory, the baby is problem-solving, interacting with the treadmilland the movement of the legs emerges.
The Meaning of Action Memory
Some of Thelens current work explores the A-not-B reaching error. In this experiment, the babies are shown two identical toys. The first toy, A, is built up in the childs memory through several minutes of play and exploration. Then the baby is shown B, the second toy, for a shorter time. When allowed to freely choose between A or B, the baby often chooses A, even though B is freshest in his or her memory. Scientists term this phenomenon perseveration.
Thelen is now trying to replicate earlier findings about perseverationthe repetition of a response, such as choosing Toy A and ignoring the new cue to Toy B. In a longitudinal study tracking babies ages 5 to 9 months, Thelen found that at 5 months, babies dont perseveratebut only half of the babies even reached at all. According to Thelen, this could be because the babies are very confused by two identical items, or their reaching isnt quite good enough at 5 months. At around 8 months, the memory that babies build up becomes stronger than the new cue, or B.
Perseveration is a good thing developmentally, Thelen says.
Were revealing that babies can build up an action memory, she explains. This is important because in order to develop a skill, babies have to be able to remember what theyve done in the past and use that movement again.
For example, in order to reach for a toy while sitting, a baby has to remember that she can only lean over so far before toppling. Once she has embedded this memory into her movement, parents will no longer need to cushion her fall.
At around age 2, a childs brain is able to hold on to the new cue more strongly, so the child doesnt perseverate as much. This ability to recognize new cues and the old habitto be flexible and stableis vital.
In some ways, I think this is the key to life, says Thelen. A person skillful in physical and mental activities as well as relationships has enough stability in behavior and memory to be consistent and reliable, but also can notice new cues.
For example, if you relate to your wife the way you related to your mother, relying on old habits, youre not very flexible.
Valeries Day in the Lab
The day arrived to introduce Valerie to science. She would be participating in Thelens efforts to replicate the nonpersever-ative tendencies of 5-month-olds.
Walking into Thelens lab is like walking into the bedroom of a well-loved child. Framed artwork of cheerful animals lines the walls, a changing table stands at the ready, and a bookcase displays rows of brightly colored toys. Located on the first floor of the IUB Department of Psychologys new 23,000-square-foot addition, the lab appears warm and fuzzy to parents and childrenbut it is outfitted with the latest video equipment, computers, and other high-tech tools to conduct studies using surface electromyography, a process that involves attaching sensors to a babys limbs to detect the electrical activity of individual muscles, then using a computer to analyze them.
Thelens postdocs and undergraduate assistants seem to adore babies and know just how to flatter their parents (Oh, shes adorable! Look at those bright eyes!). Thelen, herself a grandmother, greets us warmly and has big smiles and coos for Valerie. She clearly has a thing for babies. Our research depends on the wonderful parents and babies who volunteer to visit the lab, she says.
In the comfy chairs of the receiving area, I review the informed consent statement, which states the purpose of the experiment and what exactly will occur during it, the risks (there are noneother than the chance that Val will become bored and fussy), and the benefits (which include understanding infant reaching and helping infants whose development is not typical).
Now it is time to conduct the experiment. Thelen and I sit across from each other at a table with Valerie on my lap. Thelens assistant starts a videotape, then Thelen brings out two brown plastic lids on top of a brown box. Valeries eyes light up at the chance to put these new toys into her drooling mouth. Thelen knocks one lid (A) on the box to get Valerie interested in it and then places the lid in front of Valerie and off the brown box. Valerie goes for it and puts it in her mouth. Thelen repeats this sequence many times, then switches to the other lid (B), which she only shows to Valerie a few times. Again, Valerie becomes interested and reaches for the B lid.
This is great fun for Val, until both brown lids are placed on the brown box. She could choose either one to play with. If she goes back to A, that would be perseveration.
Instead of reaching for either A or B, Valerie seems to get confused by the brown lids on the matching brown boxit appears as though she cant distinguish them at all.
Sensing my dismay, Thelen is quick to explain what she thinks is going on in Vals head. This might be a visual issue, she says. The brown lids on the brown box are not distinctive enough for her, and she cant get the input. Thats pretty common.
Ah, I guess the cure for cancer will have to wait.
The Infant Motor Development Laboratory is always in need of baby scientists. If your child is between 3 months and 2 years old, contact the lab at (812) 855-0817.
Ceci Jones Schrock is a writer/editor for the IU Office of Communications and Marketing.