Experimenting with Babies Read online

  You can perform low-tech versions of such experiments by observing changes in how frequently your baby sucks on a pacifier (or on a finger) as you present various stimuli, such as pictures in a book or sounds from a keyboard. You can also help your baby make cause-and-effect associations through other combinations of actions and stimuli, such as by safety-pinning a ribbon to her pant leg that will ring a bell or jingle a toy when she kicks. Over time, she will come to learn that her kicking controls the sound, and if the sound pleases her, she will kick more frequently.

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  En Garde

  Age range: 0–3 months

  Experiment complexity: Simple

  Research area: Primitive reflexes

  THE EXPERIMENT

  Lay your relaxed, alert infant on her back. Gently turn her head to the side.

  THE HYPOTHESIS

  If you turn her head to the left side, she will extend her left arm out and bend her right arm at the elbow while clenching her right fist. If you turn her head to the right side, she’ll extend her right arm and bend the left arm at the elbow, clenching the left fist. Sometimes the baby’s legs will also move reflexively.

  THE RESEARCH

  This behavior is called the asymmetrical tonic neck reflex. Asymmetrical means the body responds differently on each side. Tonic refers to muscle tension—in this case, tension in the neck muscles. Though that’s the clinical name, the reflex has been nicknamed the fencing reflex, because the baby looks as if she’s assuming a fencing posture. The reflex was first studied in detail by German physiologist Rudolf Magnus, who studied posture and muscle tension in humans and other mammals in the early 20th century. The reflex is often present at birth or shortly after birth and disappears after several months.

  While certain infant reflexes have an obvious purpose—such as the rooting reflex, in which the baby turns its head in response to stimuli near its mouth in an attempt to nurse—the asymmetrical tonic neck reflex is more mysterious. Some researchers have theorized that it is merely a strange byproduct of a developing nervous system, having no real purpose of its own. Others suggest that these reflexive movements somehow contribute to coordinated movements later in the infant’s development.

  THE TAKEAWAY

  The asymmetrical tonic neck reflex is the showstopper of primitive reflexes. It’s the one you’ll want to show off at parties while exclaiming, “Science!” Consider this the first among many strange behaviors your child will exhibit as she progresses from newborn to toddler (and beyond). Many of those behaviors will seem fleeting, as is this reflex, which typically disappears when your baby is around 3 months old. If your baby is a newborn, try running this experiment several times over the next several months and observe whether the reflex grows stronger or fades away and whether the arm movements become quicker or slower. You might not fully understand all of your baby’s strange behaviors, but don’t let that stop you from appreciating them. Some of the weirdest things your baby will do are also some of the most amazing.

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  Happy Feet

  Age range: 0–3 months

  Experiment complexity: Simple

  Research area: Primitive reflexes

  THE EXPERIMENT

  Hold your alert newborn upright, supporting her weight by holding her under the armpits so that her feet are touching a firm, flat surface, such as a hardwood floor. Then, lean her upper body slightly forward.

  THE HYPOTHESIS

  Your baby will “walk” by moving her feet one after the other as you support her weight.

  THE RESEARCH

  The stepping reflex, also called the walking or dancing reflex, is one of several primitive reflexes present at birth. The reflex persists for a couple of months after birth and then fades away. Don’t worry, though—it will reappear as a voluntary behavior later, usually between 9 and 16 months.

  It was long assumed that the fading away of the stepping reflex a couple of months after birth is a result of brain maturation, but a 1984 study showed that it’s actually the baby’s strength-to-weight ratio that accounts for the gradual disappearance of the reflex. When your baby is a newborn, her legs will not have much fat on them, and so her muscles are strong enough to make her legs move when placed in an upright position. As the baby grows and her limbs become chubby, the increasing weight of her legs impedes the ability to make the stepping motion. But babies who had seemingly lost the stepping reflex exhibited it again when they were held waist-deep in water; the buoyancy of the water supported their weight, making leg movement easier. Researchers also noted that infants who had put on the most fat during their first weeks of life demonstrated fewer steps than infants who had less fat, which would support the hypothesis that the legs’ strength-to-weight ratio may impede the reflex.

  The fact that this stepping reflex is more continuous than once thought has implications not only for researchers who study motor development but also for those studying any type of dynamic system, in which multiple variables change at different rates over time. Indeed, partly on the basis of this experiment, researchers have suggested that a general dynamic systems theory could help shape our understanding of everything from embryological development to societal development.

  THE TAKEAWAY

  Scientists hate hidden variables subtly creeping into their seemingly well-controlled experiments. In this case, the hidden variable was the baby’s own physiology, so feel free to raise your nose in smug satisfaction that you’ve accounted for it and understand why the reflex disappears when it does. Repeating this experiment several times during the course of your infant’s first couple of months will allow you to pinpoint when the stepping eventually stops—and it will also help prepare you for the stooped posture you’ll soon assume more regularly as you help your baby learn to take voluntary steps.

  This experiment also teaches a broader lesson: Your baby will occasionally experience setbacks in certain developmental areas, but take heart. Sometimes an apparent regression is not a regression at all, but a side effect of growth in other areas.

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  A Penchant for Patterns

  Age range: 0–3 months

  Experiment complexity: Moderate

  Research area: Cognitive development

  THE EXPERIMENT

  Show your newborn baby some high-contrast patterns, such as black-and-white images of concentric circles, checkerboard patterns, or a simple drawing of a human face. Then show her some solid-colored images, such as red, yellow, or white construction paper. Make note of how long she gazes at each.

  THE HYPOTHESIS

  No matter how young your baby is, even less than 24 hours old, she will gaze longer at the patterned images than the solid-colored images, and longest at the drawing of the face.

  THE RESEARCH

  In 1963, Robert L. Fantz, a developmental psychologist studying observation patterns in babies, conducted an experiment in which newborn babies, ranging in age from 10 hours old to 5 days old, were shown patterned and solid-color images. He collected data on each baby’s length of gaze at each image—considered to be an indicator of the baby’s interest. The babies were found to gaze longest at the picture of the face, and longer at the high-contrast patterns than at solid colors. In fact, of the three babies younger than 24 hours old, all showed a preference for patterned images, and the youngest—tested just 10 hours after birth—looked longest at the face in three out of eight trials; no other image kept the baby’s attention as much.

  Fantz’s experiment provides strong evidence that the ability to perceive forms in general, and the human form specifically, is innate and that from a very early age, babies’ visual responsiveness to images varies according to the image’s complexity. The results challenged the view, prevalent at the time, that pattern recognition and differentiation don’t appear until weeks or months after birth.

  THE TAKEAWAY

  Congratulations! You’ve just
given your baby the infant equivalent of a Rorschach test. The results shouldn’t surprise you. Your face is uniquely interesting to a baby, no matter her age. So make sure to give her plenty of face-to-face time. Also, because complex, high-contrast patterns tend to hold your baby’s interest longer than simple, low-contrast patterns, give preference to the former when you make decisions about how to decorate a nursery or when you purchase toys or books for your little one.

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  Feet Lead the Way

  Age range: 0–6 months

  Experiment complexity: Moderate

  Research area: Motor skills

  THE EXPERIMENT

  Introduce a jingly toy to your baby by showing it to her and shaking it. Put the toy in her hand and allow her to grasp it. Then touch her feet with the toy. Next, place the toy near your baby so that she can grasp it if she reaches out to it. Then place the toy near your baby so that she can touch the toy with her feet if she moves them.

  THE HYPOTHESIS

  Your baby will be able to touch the toy with her feet about a month earlier than she can reach out and grasp it with her hands.

  THE RESEARCH

  It’s long been thought that babies gain control over their bodies in a top-down progression. First, they learn how to control their head movements; then their arm movements; then, toward their first birthday, they learn to control their legs and feet in order to sit, crawl, and walk. But experiments like this one suggest that babies can control their legs earlier in the process than previously understood.

  In a 2004 study, researchers placed infants in a seat that allowed their arms and legs to move freely. During some sessions, they placed the jingly toy at the infants’ shoulder height and within arm’s length, toward the middle of their bodies, so that merely raising their arms would not make contact with the toy. During other sessions, they placed the toy at the infants’ hip height and within leg’s reach, also toward the middle of their bodies. On average, the infants were able to touch a toy with their feet at 11.7 weeks, about a month before they were able to reach for and grasp a toy with their hands (at 15.7 weeks). The researchers noted that by the time the infants were able to touch the toys with their hands, they still spent an equivalent amount of time touching the toys with their feet, even though the hands have the ability to grasp the toy and the feet do not.

  The researchers postulate that babies are able to reach for a toy with their feet before they can reach with their hands because of differences in the anatomical structure of the hip and shoulder joints. The hips have a limited range of movement compared with the shoulder, which might mean the degree of control required for intentional leg movements is less than for intentional arm movements. Because the arms have a greater degree of movement than the legs, this might also mean that not only are arm movements more difficult to control but also it is less likely that a specific pattern of motion will already be familiar to the child. As with adults, practicing a particular pattern of motion—for instance, a dance step—makes it easier to perform, and so the practice that babies get making a low number of distinct leg movements (relative to arm movements) may give their legs an edge.

  THE TAKEAWAY

  Some people might be surprised by the results of this experiment, but any mom who has experienced the third trimester knows not to underestimate those tiny feet, which probably spent a good deal of time practicing kickboxing in her uterus. It’s natural to assume, though, that a baby would use her hands to reach for an object because that’s what older kids and grown-ups would do. But remember: Your baby’s developing body has a set of processes that have their own logic, which are not always what we might expect. Fortunately, as in many other cases, she’ll try to improvise.

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  Response Under Pressure

  Age range: 0–6 months

  Experiment complexity: Simple

  Research area: Primitive reflexes

  THE EXPERIMENT

  Lay your awake, alert infant on her back. With firm pressure, press down on the palms of both of her hands and hold for about a second. Then, also with firm pressure, press down on the soles of both of her feet and hold for about a second.

  THE HYPOTHESIS

  When you apply firm pressure to her palms, your baby will almost assuredly open her mouth. She is also very likely to turn her neck, and somewhat likely to draw her legs up closer to her body.

  When you apply firm pressure to her feet, your baby is very likely to extend her arms outward.

  THE RESEARCH

  The mouth-opening response to pressure applied to the palms is known as the Babkin reflex, named after Russian researcher P. S. Babkin, who studied the reflex in the mid-20th century. In a 2004 study, two pediatric neurologists sought to extend his findings by testing what additional reflex responses occur when pressure is applied to the palms and other parts of the body, such as the arms, feet, and thighs.

  They examined 106 newborns, each between 24 and 72 hours old, and found that 100 percent of the infants exhibited the mouth-opening response when pressure was applied to their palm. Nearly 90 percent turned their necks in response to the pressure, and nearly 70 percent drew their legs in. When pressure was applied to their feet, about 88 percent of the babies extended their arms outward in response. The researchers also found that infants show these and other types of reflex responses when pressure is applied to other parts of the body, such as the upper and lower arm, although in some cases only a small fraction of the babies exhibited a particular response to a particular pressure point.

  Even extremely premature babies typically exhibit the Babkin reflex shortly after birth, so it’s considered a fairly reliable indicator of reflex response. The researchers in the 2004 study note that the fact that multiple pressure points can cause a variety of reflex responses is useful knowledge for medical providers who are trying to assess a baby’s neurological condition, because it gives them alternate ways to investigate the baby’s reflexes aside from the standard Babkin procedure.

  THE TAKEAWAY

  For parents, the Babkin reflex has a very practical use. In cases when a newborn is not feeding well, pressure can be applied to her palms to get her to open her mouth and nurse or take a bottle. You might feel as if you’re treating your baby like a marionette, but when the kid ain’t eating, sometimes you’ve gotta do what you’ve gotta do.

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  I’m Hip to That

  Age range: 0–9 months

  Experiment complexity: Simple

  Research area: Primitive reflexes

  THE EXPERIMENT

  Lay your baby on his stomach and stroke either the left or the right side of his back, near (but not on) the spine.

  THE HYPOTHESIS

  If you stroke the left side of his back, his left hip will rotate; if you stroke the right side, his right hip will rotate.

  THE RESEARCH

  This primitive reflex, present at birth and fading away by about 9 months of age, is called the spinal Galant reflex, named after Johann Susmann Galant, who first described it in the early 20th century. For some people, it persists past this point and can even last into adulthood. In school-aged children who still exhibit the reflex, it has been linked with certain developmental problems, such as bedwetting and difficulty sitting still. However, movement therapy can help address some of those problems. For instance, in a 2000 study, school-aged children who had persistent infant reflexes were assigned movement exercises aimed at helping them bring the reflexes under voluntary control. After a year of the exercises, they showed a marked decrease in their reflex responses and an increase in several academic measures, such as reading and writing skills, versus children in control and placebo groups.

  At first glance, the spinal Galant reflex may not seem to have much utility, but it actually serves an important purpose during labor and delivery: The motion of the hips in response to stimulation to the back is thought to help the baby mov
e through the birth canal.

  THE TAKEAWAY

  Sure, this sounds like a fun reflex to experiment with, but once your baby has arrived, you’ll likely be thinking, “Why on earth would I want to make my baby wiggle more?”