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chapter5.docx5.1 Nutrition, Growth, and Survival in Infancy
Even if they are never dropped on their heads, in the beginning, infants are seemingly very poorly equipped for life's journey. They are almost completely helpless physically: They can't move somewhere else, control ambient temperature, or clean themselves; and they have no protection against wild dogs, vultures, one-eyed cats, or clumsy caregivers. They can't even find food unless it is put under their very noses. Once they find it, though, they suck. Sucking is a primitive reflex—one of those simple, automatic, unlearned behaviors—present at birth in virtually all mammals.
Breast-feeding
The sucking reflex is what ensures the infant's survival—that and the presence of a lactating mother. In fact, physicians pretty well universally recommend that the infant needs nothing other than a lactating mother for six months or longer (Breastfeeding, 2011).
But it seems that for many years there has been a quiet battle over breast-feeding—a breast versus bottle battle. On one side are the mothers who, for a variety of reasons, choose not to breast-feed their infants. On the other are a legion of physicians and philosophers. Their arguments for breast-feeding have varied through history. In early times, many insisted that breast-feeding is something all animals do; it is therefore natural and good. Others appealed to religion and duty, convinced that suckling is the child's sacred birthright and the mother's solemn duty. Still others believed that maternal virtues and morals might be transmitted through breast milk (Kessen, 1965). (So, do the virtues and morals of cows get transmitted through cow's milk?)
More recently, physicians invoke an impressive list of medical reasons to support their recommendations. Mothers' milk, science tells us, is the best of foods for most newborns. It contains just about the right combination of nutrients, the near-exact proportion of fats and calories, the almost-perfect assortment of minerals and vitamins. Furthermore, it is easier for infants to digest than cow's milk, and less likely to lead to allergic reactions. Also, it provides infants with a high degree of immunity against many infections and diseases, and especially against diarrhea, one of the principal causes of infant mortality in the developing world. The breast-fed infant's increased immunity is apparent in greater resistance to a variety of diseases, including cancer and respiratory diseases (Melendi et al., 2010). And, not least important, human milk contains nutrients that are essential components of tissues such as the brain and the retina (Singhal et al., 2010).
Though most of the arguments for breast-feeding have emphasized its benefits for the fetus, there are also strong arguments to be made for its positive effects on the mother. Among them is the fact that the hormone, oxytocin, released during breast-feeding, is highly effective in preventing postpartum hemorrhaging, and in stimulating the return of the uterus to a nonpregnant state (termed involution). In addition, breast-feeding typically delays menstruation. This helps the breast-feeding mother retain essential iron stores and also serves as a natural means of spacing pregnancies. Whereas non-breast-feeding mothers may become pregnant again as soon as 6 weeks after delivery, extremely few lactating mothers can become pregnant for at least 6 months. In addition, breast-feeding is linked with reduced risk of breast, uterine, and ovarian cancers; it is associated with weight loss; it lessens osteoporosis; and it may have a variety of psychological benefits (Dermer, 2001). It is also considerably less expensive than formula feeding.
In spite of the many advantages of breast-feeding, it is far from universal. And there are many valid reasons why a mother might choose not to breast-feed her infant, including painful breasts, infants rejecting the breast, and a variety of commitments typical of today's busy mother. Also, bottle feeding allows fathers to be more intimately involved in the care of their infants.
It would be misleading not to emphasize that in much of the industrialized world, where sanitation and nutrition are excellent, bottle-fed infants thrive. Also, it is worth noting that breast milk is affected by the mother's intake of food and drugs, as well as by chemicals to which she is exposed. Alcohol, nicotine, barbiturates, stimulants such as caffeine, sedatives, and prescription drugs can each have an effect on breast-fed infants. There is evidence that HIV infections can sometimes be transmitted to the infant through breast-feeding (Kourtis & Bulterys, 2010). Though some of these may be poor reasons not to breast-feed, it appears that there are circumstances under which an infant's journey might start out much better if fueled with milk from a cow or a goat or a prepackaged formula.
Nutrition and Physical Growth
Physical growth in infancy is relatively predictable, given adequate nourishment (Figure 5.2) In contrast, malnutrition, both in the prenatal and early postnatal periods, often leads to growth retardation and maturational delays (Martorell, 2010). Note that malnutrition is not synonymous with starvation and hunger. It involves not getting the right combination of vitamins, minerals, and other nutrients, and can therefore occur even when there is plenty of food.
Because of our different genetic programs, identical nourishment will not make all infants exactly the same at all ages. Some will be very close to the averages shown in Figure 5.2; others may be well above or below average.
How much below average is a cause for concern? The somewhat arbitrary answer is in approximately the bottom 2.27 percent. Children who are in the bottom 2.27 percent for height are, by definition, suffering from stunting; wasting is defined as being in the bottom 2.27 percent for weight. Sadly, in the world's developing countries, more than 32 percent of children under age 5 are classified as stunted (Progress for Children, UNICEF, 2011) (Figure 5.3).
The World Health Organization estimates that well over half of all children born in third-world countries suffer from malnutrition. Most serious is protein undernutrition, which may have long-term negative effects not only on physical growth, but also on cognitive functioning. Serious protein deficiency in infancy is sometimes evident in the condition labeled kwashiorkor. In serious cases, kwashiorkor is marked by extreme wasting and stunting, listlessness, unresponsiveness, and sometimes death. In less severe cases, its effects are apparent in smaller physical size as well as in cognitive deficits later in childhood (Galler et al., 2010).
Malnutrition is far less common in industrialized countries despite significant numbers of mothers and children living in poverty and many children not having enough to eat. Although few of these children suffer from kwashiorkor, many might be more likely to reach their full human potential, not to mention have happier journeys through life, if their bellies were always as warm and full as they should be.
Sudden Infant Death Syndrome
First formally defined in 1969, sudden infant death syndrome (SIDS) is the sudden and unexpected death of an infant who has seemed well, or almost well. This mysterious cause of infant death accounted for approximately 1.5 deaths for every 1,000 live births as recently as 1980. Now that figure has been reduced to less than 1 per 1,000 (Chang, Keens, Rodriguez, & Chen, 2008).
Although research hasn't yet determined the precise causes of SIDS, it has identified a number of characteristics shared by many victims. Most striking, SIDS occurs during a far narrower age span than almost all diseases: It is extremely rare in the first several weeks of life, peaks between 2 and 4 months, and falls rapidly to age 6 months. SIDS deaths are uncommon after the age of 1 year.
Other risk factors for SIDS include sex, with males accounting for about 60 percent of cases. There is evidence, too, that SIDS may be slightly more probable among infants whose siblings have been victims. Bundling infants in layers of clothing, maternal smoking, and bacterial infection are other possible related factors (Salihu, Hamisu, Wilson, & Ronee, 2007; Highet, Berry, & Goldwater, 2009).
Perhaps most important for SIDS prevention is sleeping position. Infants who are put to sleep on their sides or on their backs (in a supine or face up position) are at far lower risk for SIDS than infants who sleep prone (face down, on their stomachs.) In fact, the reduction of SIDS deaths by more than one-third is attributed largely to medical advice to this effect (Dwyer & Ponsonby, 2009)
5.2 Brain Growth and Motor Development
For many years, what we knew about the brain was based mostly on what had been discovered by looking at the brains of people who had died, or by looking at the behavior of people who had suffered brain injury. Now scientists have access to powerful brain-imaging techniques, such as functional magnetic resonance imaging (fMRI), which allow them to examine the physical structure and activity of intact brains in unobtrusive ways.
Investigations of brain development and activity reveal several important facts: For example, we know that the vast majority of the brain's cells—more than 200 billion neurons—are formed during the first four months of prenatal development. And we also know that optimal brain development is influenced by two important factors: One is sensory and cognitive stimulation; the other is nutrition (Guerrini, Thomson, & Gurling, 2007). Protein and certain fatty acids (which are present in milk, especially human milk, but not ordinarily in infant formulas) are especially important to normal brain development during the prenatal period and in the first year of life (de Souza, Fernandes, & do Carmo, 2011). Deficiencies in iron, iodine, and vitamin A may also be implicated in poorer mental development (Melse-boonstra & Jaiswal, 2010).
During the final several weeks of fetal development, the absolute weight of the brain increases dramatically. At birth, the brain already weighs about one-quarter of what it will weigh at adulthood, whereas the newborn's total weight is only about one-twentieth of what it will eventually be.
Brain Structure and Development
Although the brain is relatively large at birth (approximately one-quarter the size of the rest of the body, compared with an adult ratio of about 1 to 8 or 10), most of its billions of cells are not yet connected to each other—except for the brain stem, where networks of cells are programmed for activities such as breathing, sleeping, and temperature control.
The very large brain of the newborn—and the adult—consists of three main parts (Figure 5.4). The brain stem, which is an extension of the spinal cord, is the most highly developed brain structure at birth. It deals mainly with physiological functions such as breathing and heart action. The cerebellum, a structure found low at the back of the brain behind the brain stem, is concerned with balance and with sensory and motor activity. The cerebrum is the largest and most complex brain structure. It divides naturally into two halves (brain hemispheres). Its outer covering, the cerebral cortex, is the convoluted and wrinkled grayish surface that would be immediately visible if the skull were opened.
The cerebrum makes up about 75 percent of the total mass of the brain, and its functions are among the most important in determining what it is to be human (thought, language, vision, and sensation). It is the most recent brain structure from an evolutionary point of view, and also the latest to develop in the fetus. Those parts of the cerebrum that are concerned with thought continue to grow and develop into early adulthood.
The cerebral cortex (the thin outer covering of the cerebrum) has deep fissures (indentations) that divide into four distinct lobes: the parietal lobes; the frontal lobes; the temporal lobes; and the occipital lobes. The main functions of these lobes are shown in Figure 5.4.
The major early developments in the brain have to do mainly with its system of interconnections. The brain, as well as the rest of the nervous system, is composed of billions of neurons (nerve cells), whose function is to transmit impulses in the form of electrical and chemical changes. Transmission occurs through interconnections that form among neurons. Each neuron consists of a cell body, an elongated part (the axon) surrounded by a protective coating (the myelin sheath), and hair-like extensions (dendrites). Neural transmission ordinarily proceeds from the cell body outward along the axon, at the end of which the impulse (message) jumps the gap—termed a synapse—to the dendrites of adjacent neurons (Figure 5.5). Bundles of neurons make up nerves.
The brain continues to grow very rapidly during the first two years, reaching about 75 percent of adult weight at the end of that period. The very rapid development of the brain that occurs during this time does not involve the formation of new neurons, but rather the development of new connections among them—a process highly dependent on stimulation from experiencing the world and from social interaction. What this brain proliferation means is that by the age of 2, the infant brain has an enormous number of potential connections among brain cells. These connections are what make it possible for 2-year-olds to learn so much so rapidly. And perhaps nowhere is the staggering potential of this brain more evident than in the learning of language.
Interestingly, the brain of the 2-year-old may contain more potential connections than it will ever contain again. It is likely, explains Johnson (2000) that the billions of connections that aren't used eventually disappear—a process referred to as neural pruning.
The Role of Experience
This is where experience comes in. The human brain is extraordinarily dependent on experiences if it is to develop normally. It seems that in the absence of appropriate stimulation early in life, far more of these billions of connections will be lost than would otherwise be the case. Environmental events, such as exposure to language, are critical to the development of the brain (Fox, Levitt, & Nelson, 2010). This is clearly illustrated in experiments with animals. For example, Rosenzweig (1984) found that rats raised in enriched environments have significantly heavier brains than rats raised in impoverished environments. And kittens who are not exposed to visual stimulation for the first several weeks of their lives (their eyes are sewn shut or they are blindfolded) lose most of the neural connections usually associated with vision and never learn to see normally (Hubel, 1988).
For ethical reasons, experiments such as these cannot be conducted with humans. However, measures of brain structure and functioning in a group of preterm newborns found significant benefits of enriched stimulation during the first two weeks of life (Als et al., 2004). Similarly, studies of Romanian orphans exposed to highly deprived environments during their first years reveal dramatic differences between their brains and those of normal children (Eluvathingal et al., 2006).
As a result of findings such as these, some researchers suggest that there are distinct periods of very rapid brain growth during which exposure to appropriate environmental stimulation is critical for later learning and the development of intelligence (Dawson, Ashman, & Carver, 2000). Not surprisingly, the most dramatic spurt in brain growth occurs early in the first year of life. That Genie Wiley, the abandoned child described in Chapter 3 and again later in this chapter, did not develop normal language skills after she was rescued may be evidence that there is a critical period during which exposure to language results in far more rapid and effective learning. It is as though there are certain paths that must be followed early in the journey or they may never be found again.
The Brain and Infant States
One of the important functions of the brain during early infancy is to control the infant's general condition—that is, the infant's physiological arousal or infant state. Following a detailed study of infant behaviors, Wolff (1966) describes six distinct infant states: regular sleep, irregular sleep, drowsiness, alert inactivity, alert activity, and crying (these last two states are sometimes grouped together and termed focused activity. Note that these are essentially descriptions of central nervous system activity. Newborns vary considerably in the amount of time spent in each state (Figures 5.6 and 5.7).
Motor Development in Infancy
Within hours of birth, beavers are able to dive, hold their breaths, and swim; young antelope can run with the herd; and baby geese can follow their mothers. These animals are precocial (born with highly developed motor capacities.)
In contrast, human infants are altricial (born relatively immature). They cannot walk or even control the movements of their hands or their heads. As a result, they remain physically helpless for a prolonged period of time.
Reflexes
In the very beginning, the newborn cannot initiate intentional behaviors, capable only of reflexes—simple, unlearned behaviors that are present at birth. In a sense, reflexes are automatic and essentially unavoidable reactions to stimulation. Some reflexes, such as the breathing reflex, the sucking reflex, and the rooting reflex are survival reflexes—as are swallowing, hiccuping, sneezing, and vomiting.
Other reflexes, such as the moro reflex—a generalized startle reaction that involves throwing out the arms and feet symmetrically—have no apparent survival value today. However, some speculate that this reflex might have saved the lives of unlucky tree-dwelling primate infants who fell unexpectedly. In normal infants it, like the palmar reflex (also called the Darwinian or grasping reflex), the swimming reflex, and the stepping reflex, disappears early in infancy—as does the Babinski reflex (Table 5.2).
The development of the infant's early motor skills is closely related to early reflexes. Thus learning to crawl is an extension of the swimming reflex, just as learning to walk and learning to grasp are extensions of the stepping and the palmar grasp reflexes. Some of these motor accomplishments involve gross motor development (skills related primarily to large body movements such as crawling, standing, and walking). Fine motor development refers to the development of control over smaller (finer) movements (hence smaller muscle groups such as those involved in grasping and stroking).
The order in which children acquire motor skills is highly predictable, although the ages at which these skills appear can vary considerably. Descriptions of developmental milestones and norms, such as shown in Figure 5.8, are sometimes useful for assessing a child's progress. However, as always, there is no "average" child; each is unique.
The normal sequence of motor development reflects two broad developmental principles: First, development is cephalocaudal—meaning it proceeds from the head toward the feet. For example, infants can control eye movements and raise the head before acquiring control over the extremities. Fetal development proceeds in the same manner in that the head, eyes, and internal organs develop in the embryo before the limbs appear.
Second, development is proximodistal (near to far): it proceeds in an inward-outward direction. For example, internal organs mature and function before the (more external) limbs develop. Similarly, children can control gross motor movements before hand or finger movements.
Cultural Variations
Although the sequence of early motor development reflects a genetically influenced timetable, the infant's context can dramatically influence both the ages at which different motor skills are acquired and their quality. For example, Gerber (1958) reports an investigation of 300 Ugandan infants who, a mere two days after birth (all home deliveries without anesthetics), could sit upright, heads held high, with only slight support of the elbows—a feat that most American children cannot accomplish until close to the age of 2 months. And all 300 Ugandan children were expert crawlers before they were 2 months old (as opposed to between 6 and 9 months for American children)!
What accounts for these differences? A variety of factors, explains Adolph (1997). Genetic factors, perhaps reflected in the infant's activity level as well as in distributions of muscle and fat, appear to be clearly important. For example, newborns with chubbier legs often learn to walk later than do those with more slender legs.
At the same time, however, experience is clearly important. Ugandan infants, many of whom are typically held upright and carried around by their mothers, may learn much about locomotion both visually and in terms of their bodily sensations of the mother's movements. Similarly, children adopted from Eastern European orphanages often display markedly delayed motor development, a circumstance attributed to them being often left in their cribs or lined up on benches for extended periods with little or no opportunity to practice the skills involved in locomotion (Judge, 2003).
Motor Skill Disorders
Not all children learn to walk or tie their shoes or dance as expected; some experience a variety of physical and motor problems, sometimes evident in cerebral palsy and other conditions.
Cerebral Palsy
Cerebral palsy, also labeled significant developmental motor disability, is a nonprogressive, noncontagious condition reflected in motor problems that cause physical disability of varying severity. It may also include psychological problems, convulsions, or behavior disorders. It varies in severity from being so mild that it is virtually undetectable, to paralysis.
Cerebral palsy is most often a congenital disease—that is, it is present at birth in more than two-thirds of all cases. It is associated with brain damage—the reason for the label cerebral—although the damage is often mild and nonspecific. Sometimes it results from anoxia (lack of oxygen during the birth process, or before or after birth). It can also result from either maternal infection and disease or postnatal brain injury sometimes caused by diseases such as meningitis or encephalitis (Bjorklund, 2006). Not surprisingly, prematurity is a significant risk factor for cerebral palsy (McCormick, Litt, Smith, & Zupancic, 2011).
Cerebral palsy is the second most common developmental disorder among school children in the United States (mental retardation is more common). Estimates of its prevalence are imprecise because many of the milder cases are not reported and because there is no "cure" for the condition. In the United States, there are about 3 cases for every 1,000 live births. Of these, perhaps half also have other developmental disabilities (National Center on Birth Defects and Developmental Disabilities, 2004).
One of the most common signs of cerebral palsy is spasticity (inability to move voluntarily) in one or more limbs. Physical therapy is sometimes effective in improving motor control and coordination.
Language disorders are also relatively common. These motor and language impairments are sometimes so severe that it is difficult to assess a child's intellectual ability. As a result, it was often assumed that intellectual deficits are common among those suffering from cerebral palsy. However, more recent evidence suggests that fewer than half of cerebral palsy victims are mentally retarded (Mesterman et al., 2010).
Other Motor Skill Disorders and Physical Problems
There are other motor skills disorders not associated with brain damage or cerebral palsy. These are often evident in delayed development among children, many of whom also have other developmental disorders, such as mental retardation, autism, or even attention-deficit disorders. Motor disorders may be apparent in difficulties in learning tasks such as walking, running, skipping, and tying shoes; they may also be apparent in difficulties in carrying out motor activities. A common label for these problems is developmental coordination disorder.
According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) of the American Psychiatric Association, a developmental coordination disorder exists when (1) a person's performance of activities requiring motor coordination (such as crawling, walking, sitting, handwriting, sports) is markedly below what would be expected for the child's age, (2) the disturbance interferes with academic achievement or activities of daily living, and (3) the disturbance is not due to a known physical disorder (such as cerebral palsy) (American Psychiatric Association, 2000).
5.3 Sensation and Perception in Infancy
Our journeys as human beings depend largely on our ability to make sense of the world and ourselves. We need to be able to sense and to know what is out there. The struggle to discover what things are and what they mean begins in infancy and depends on three closely related processes: sensation, perception, and conceptualization.
Sensation is the effect of physical stimuli on the senses; it involves activity of one or more specialized sense organs—eyes, ears, and taste receptors, for example.
Perception is the brain's interpretation of sensation. We perceive the color red when wavelengths corresponding to that color cause a specific reaction in our retinas, leading to the transmission of impulses to the part of our brain that deals with vision. Thinking about that color red, comparing it to other colors, or making some decision based on it is a function of the third process, conceptualization, which is a more cognitive or intellectual activity.
Because these three processes—sensation, perception, and conceptualization—are basic for understanding the world, knowing about their functioning and their development is important for understanding what infants experience.
Vision
How well can an infant see? Is the world fuzzy and blurred, or is visual acuity 20/20, making the world crisp and clear? Research with infants isn't always easy (Figure 5.9), nor do researchers always agree, but a number of things seem clear.
First, vision is probably the least well developed of the infant's senses. Visual acuity, that is the sharpness of the newborn's vision, is estimated to be about 20/400, or perhaps even 20/600 (they can see at 20 feet what people with normal vision see at 400 or 600 feet). Hence neonates' visual worlds are somewhat fuzzy and blurred, although they are far from blind (Valenti, 2006) (Figure 5.10).
Second, there is roughly a five-fold improvement in an infant's visual acuity by the age of 6 months (Courage & Adams, 1990). Now the infant sees as clearly at 20 feet what the adult sees at 100 feet. And by the age of 1 year, infant visual acuity is close to that of a normal adult. But it's important to note that improvement in vision is highly dependent on early experience. Stroganova and Tsetlin (1998) report that infants born with cataracts in both eyes experience significant developmental delays, even after the cataracts are surgically removed at around 8 months.
Third, a newborn's visual accommodation is more limited than that of adults. It appears that newborns focus most accurately at a distance of approximately 8 to 12 inches (Banks, 1980). Significantly, that is about the distance of a mother's face when she is feeding her infant.
Perception of Depth
In the famous Gibson and Walk (1960) "visual cliff" studies, a heavy sheet of glass is positioned over a checkered surface, but only half of this surface is flush with the glass; the other half is some three feet lower (Figure 5.11). An adult standing or sitting on the glass can plainly see a drop where the patterned surface falls away from the glass. So can goats and human infants. At the age of only 1 day, baby goats avoid the deep side, either going around it or jumping over it when they can. And even when their mothers call them from the other side, human infants who are old enough to crawl typically refuse to cross the deep part. Thus perception of depth is present at least from the time that the infant can crawl.
Visual Preferences
We know that young infants see, although somewhat fuzzily in the beginning. We know, too, that they have limited perception of color for the first few months, but that they prefer bright colors over plain white (Zemach & Teller, 2007). Also, they are capable of detecting motion and of visually following moving objects very soon after birth. Do they also have preferences with respect to what they look at?
The answer is yes. In one study of infants' visual preferences, 18 infants, aged 10 hours to 5 days, were shown six circular stimulus patterns of different complexity, the most complex being a human face (Fantz, 1963). The face was looked at for a significantly higher proportion of total time, indicating not only that infants can discriminate among the various figures, but also that they prefer faces—or perhaps that they prefer complexity.
Subsequent research suggests that infants are predisposed to attend to faces. And very soon, they show a distinct preference for the female face and for faces of their own ethnic origin. It seems, argue de Haan and Nelson (1997), that infants are born with some innate knowledge about faces that allows them to recognize and be attracted to them. They suggest that this propensity is probably closely tied to the importance of recognizing primary caregivers if the infant is to form an attachment to them.
Hearing
Dogs, bears, cats, and many other animals are deaf at birth; the human neonate is not. It appears that the ear is fully grown and potentially functional a few months before birth, and that the fetus can hear sounds (Lecanuet & Schall, 2002). In fact, most investigations indicate that neonates are extraordinarily attuned to hearing human speech sounds and to discriminating among them. Amazingly, even at the age of 3 days, infants are able to discriminate among different voices and seem to prefer the sound of the mother's voice. In a study in which systematic changes in an infant's sucking were reinforced with the sound of a woman reading a book, the infant responded most strongly to its mother's voice (DeCasper & Fifer, 1980). By the age of 6 months, infants have not only learned to discriminate a wide variety of human sounds, but have also begun to assign meanings to many of them.
Smell, Taste, and Touch
Smell is one of the most important senses for the earth's animal species. Without a powerful sense of smell—and of taste—most animals would be in grave danger of not finding food or of poisoning themselves. It should hardly be surprising that newborns are highly sensitive to odors, as well as to tastes and touch.
Within hours of birth, newborns turn their faces away when exposed to a strong and unpleasant smell such as ammonia (Lipsitt, Engen, & Kaye, 1963). And they smack their lips when sweet things are placed on their tongues and pucker their mouths in response to sour tastes. As grandmothers have long suspected, and as science has now confirmed, giving crying newborns sucrose is often effective in quieting them; giving them lemon leads to an expression of distaste; and giving them plain corn oil or water has little effect (Graillon, Barr, Young, Wright, & Hendricks, 1997).
Earlier investigators had concluded that the neonate is remarkably insensitive to much of the stimulation that children and adults would find quite painful. Circumcision doesn't really hurt boy babies, they assured us. But they were probably at least partly wrong: Boy babies do holler when circumcised! And more recent research indicates that neonates are sensitive to pain (Fitzgerald & Walker, 2006).
5.4 Memory in Infants
We know that infants are born with an impressive array of cognitive tools—tools that will eventually allow them to know and understand things of which they cannot yet even dream. They can look and see; they can hear; they can smell and taste. And more impressive than anything else, they have an astonishing brain. In fact, everything we have learned about infants thus far reinforces the view that they are remarkably ready to learn.
But ready though they might be, they know so little; there is so much to learn and so little time to do it if they are to be as competent at the age of 2 as most of them will surely be. How do they learn? What do they learn? How do they remember? What do they know in the beginning and what do they know at the end?
Studying Infant Memory
If neonates, ignorant and helpless as they are at birth, are ever to reach the level of competence of the 2-year-old, there is much that must be organized and stored in their memory: They must learn and remember what is edible and what isn't; how to get from here to there; how to ask for things; how to hold a cup; how to get people's interest and attention; and much more.
A neonate's memory does not appear to be nearly as efficient and powerful as yours or mine. Nor is it an easy thing to study, given that pre-verbal infants cannot easily tell the investigator what they remember.
The Orienting Response and Habituation
One way of investigating infant memory is to look at the orienting response—the tendency of most organisms to respond to new stimulation by becoming more alert—that is, by attending or orienting to it. In dogs, the orienting response is clear. On hearing a new sound, a dog will pause and its ears may perk up and turn slightly toward the sound; its attitude says, in effect, "What the %$*#@ was that?"
The human infant does not respond so obviously, but distinct and measurable changes take place, including alterations in pupil size, acceleration or deceleration of heart rate, and changes in the electrical conductivity of the skin. Together, these changes define the human orienting response.
The value of the orienting response is that it signals attention because it occurs only in response to novel stimulation to which the infant is then attending. It can also be used as an indication of learning because when an infant has learned a stimulus (when it has become familiar), the orienting reaction decreases or disappears—a phenomenon termed habituation. In a simple study of memory, for example, researchers might look at an infant's response to a photograph (or other stimulus) presented on two different occasions. If the infant remembers something about an already-seen photograph, heart rate would not be expected to change in the same way as it initially did.
When infants are older, memory can often be studied by looking at behaviors they can now control. For example, Rovee-Collier and Hayne (1987) report a study in which 3-month-old infants learned to make a mobile turn by moving their feet. Infants remembered the procedure several weeks later.
Characteristics of Infant Memory
Using these various approaches, investigators have found that even newborns have memories. For example, Swain, Zelazo, and Clifton (1993) had 1-day-old newborns listen to a word and then monitored them as they turned their heads toward the sound. Within a short period of time, these infants habituated to the word and stopped turning. One day later, half these infants were again exposed to the same word; the other half heard a different word. Again, all infants initially oriented to the word, turning their heads toward it. But those who were exposed to the same word both days habituated significantly more rapidly than those who heard a new word—clear evidence that they remembered something of the word.
Still, evidence suggests that an infant's memory for most things appears to be relatively brief. Young infants who are conditioned to associate a puff of air with a tone, or a feeding schedule with a bell, may remember from one day to the next. But without any reminders in the interim, all evidence of memory is likely to be gone within a few days.
It seems clear that memories of very young infants are far more fragile than adult memories; they are far more likely to be lost. Yet, by the age of 18 months to 2 years, infants' long-term memories are quite remarkable—as is evident in the fact that by that age, most have learned, and will remember, hundreds of words (Rovee-Collier & Cuevas, 2009). It's true, however, that they will be reminded of these words repeatedly. And it's also true that, in the end, they will consciously remember virtually nothing of any of the specific experiences they have had as children. In fact, we all seem to be victims of this strange phenomenon labeled infantile amnesia: Our early autobiographical memories (memories for personal experiences, tied to a time and place) are typically lost to infantile amnesia. Even 6-year-olds are hard pressed to recollect memories they had clearly in mind two years earlier (Peterson, Warren, & Short, 2011).
There is, as yet, no agreed-upon explanation for this fact (Bauer, Larkina, & Deocampo, 2011). One theory is that parts of the infant's brain associated with memory are insufficiently mature to permit long-term remembering; another is that the infant's memory strategies are too primitive to allow the organization and associations required.
There is a great gulf between the immature memory of the week-old child who can demonstrate a vague recollection of a familiar smell or sound, and that of the 1-year-old who mistakenly yells "Dada" when he sees a stranger's familiar-looking back in the supermarket. There is also a vast difference between this 1-year-old's memory and the memory of an 8-year-old, whose intellectual strategies permit mental feats the 1-year-old cannot even imagine. (See Chapter 7 for more information about memory.)
The infant's rapidly developing memory makes possible a range of intellectual achievements that we, as adults, tend to take for granted. Memory, as Howe (2011) explains, is the basis of adaptation and survival. That I recognize my computer this morning, that I can anticipate the contents of this file before I open it, and that I can intend to say to you what I am saying at this very moment—none of these things would be possible if I had no reliable memory of these matters, or if I did not know that I can control the actions that will turn my intentions into realities.
Matters are not exactly so for young infants. Not only are they unable to control their actions, but they also have little understanding of intention, of how actions can deliberately be guided toward goals. Perhaps even more basically, they have yet to realize that objects in the world are real and permanent, that they have an independent existence.
5.5 Infant Cognitive Development
As Piaget explains, infants have not yet developed the object concept. The world of the infant is a world of the here and now. The nipple exists when the infant sees, touches, or sucks it; when it can't be sensed, it is gone from memory and has ceased to exist.
Imagine what the world would be like, suggest Wellman and Gelman (1992), if we thought objects disappeared and reappeared. The object concept, they explain, is absolutely fundamental to our reasoning about the world; our very conception of the world demands that objects be real, out there, substantive, and independent of us. There is no "out there" for infants; they must discover the permanence and objectivity of objects for themselves. This discovery is one of the truly great achievements of infancy.
To investigate infants' understanding of objects, Piaget (1954) showed them an attractive object and then hid it. If the object exists only when infants perceive it, reasoned Piaget, they will make no effort to look for it when they can't see it even if they actually saw it being hidden. Looking for a hidden object is clear evidence the child can imagine it and believes it still exists.
Piaget found that young infants do not respond to the object once it is removed. But by about 8 months, they begin to look for the object if it has just been hidden. If a few seconds have passed, they are likely not to search at all. And if an object is hidden in one location—say under pillow A—and then moved to a second location—say pillow B—in full view of the child, even a 12-month-old is likely to search only under pillow A and abandon the search when the object isn't found. This is known as the A not B error.
According to Piaget, this demonstration, replicated many times, illustrates that before the age of 18 months the infant has an incomplete and somewhat fragile understanding of the permanence of objects. But other investigators have argued that Piaget's test may not be entirely convincing, and that other approaches might lead to different observations. For example, Baillargeon and DeVos (1991) arranged for a short or a long carrot to move behind a windowless yellow screen on a track so that the carrots disappeared from the infant's view. When the infant had habituated to these two events (that is, looked at them for about the same time), the windowless yellow screen was replaced with a blue one that had a window cut out of the top. The short carrot would still not be visible as it passed behind the screen, but the tall one should be. That it isn't (due to the experimenters' surreptitious manipulations) would only be surprising if infants expected it to be (see Figure 5.12). Apparently, even at the age of 3.5 months, many infants stare longer at this "impossible event," as though surprised by it.
Do these observations mean that Piaget was wrong and that infants have a notion of the permanence and independent identity of objects long before the age of 18 months? Not really. What they indicate is that under the right circumstances, infants appear to have a short-lived recollection of absent objects, and have begun to understand that objects are solid and stationary.
Though it isn't entirely clear how infants learn about the solidity and permanence of objects, and about how they move, Rakison and Lupyan (2008) argue that it depends on experiencing objects in the real world, and also on, in their words, "advances in information-processing abilities such as improving short- and long-term memory" (p. 9).
Although it's probably true that Piaget underestimated the ages at which infants might begin to achieve the object concept, Haith (1998) suggests that researchers are often guilty of the opposite error: They are guilty of too "rich" an interpretation of infant cognition. For example, on the basis of a few additional seconds of looking at a presumably impossible situation, we want to infer that infants understand things about objects that they probably don't. Even though 4-month-old infants might seem surprised at the disappearance of expected objects, it will be a long time before they begin to look for these objects even when someone has hidden them before their very eyes.
Intention, Imitation, and Morality in Young Infants
Looking for a hidden object presupposes more than the realization that the object is permanent—that it does, in fact, exist under the pillow or in the hall closet. It assumes as well that the infant is capable of forming the intention of searching for it, and is also capable of acting out that intention.
In its ordinary sense, intentional means purposeful or deliberate. The laws of many societies assume that infants, and even much older children, are incapable of immoral acts simply because they are incapable either of forming prior intentions or of understanding the implications of their behaviors. Discovering when infants are capable of intentional behavior has been an important challenge for developmental psychologists. (See In the Classroom: Bad, Albert. Bad.)
At first glance, this seems a difficult undertaking, given that preverbal infants cannot explain their intentions or their goals. Still, infants do many things that show at least the beginnings of intention. For example, they quickly learn to follow someone else's gaze to see what they're looking at. This sort of "joint attention," says Flavell (1999), is an important precursor to intentional communication. Also, infants look at, point to, or hold up objects apparently with the intention of having someone else react. Finally, infants' persistent attempts to imitate provide clear evidence of intention.
Imitation, as we saw in Chapter 2, is one of the important ways of learning new things or modifying old behaviors. In some ways, it appears to be a natural way of learning. But is it? Can newborns imitate?
Some researchers think yes; others don't agree. For example, Meltzoff and Moore (1989) report that at a mere 2 weeks of age, infants are already able to imitate simple actions such as sticking out the tongue or opening the mouth wide. But others suggest that neonates aren't actually imitating when they stick out their tongue or purse their lips in apparent response to a model. Instead, they might simply be manifesting a generalized, almost reflexive, response related mainly to feeding (Kaitz, Meschulach-Sarfaty, Auerbach, & Eidelman, 1988).
It is highly telling that one of the few behaviors that infants younger than 1 month seem to be able to imitate (and often very badly, or not at all), is tongue protrusion (Perra, Parisi, & Caffarelli, 2008)—a behavior closely linked with the rooting, sucking, and swallowing reflexes. After the age of 1 month, this "imitative" behavior declines significantly.
Imitation in Older Infants
It is also significant that the infant is initially capable of imitating only when the model is present or has just left. Piaget (1951) suggests that deferred imitation—the ability to imitate something or someone no longer present—is not likely to occur before the age of 9 to 12 months. The ability to imitate an action after the fact is strong evidence of the infant's ability to represent mentally.
The second year of life is a crucial period for the infant's burgeoning ability to represent mentally and to imitate. Now infants begin to imitate novel actions. Imitation provides a powerful tool for new learning—and especially for learning language. Nor is the older infant's imitation limited to imitating and learning only from adults. Toddlers (older infants) imitating other toddlers is highly evident in child-care facilities.
Studies of infant imitation provide impressive evidence of the infant's growing ability to make inferences about other people's intentions. For example, Meltzoff, Gopnik, and Repacholi (1999) had 18-month-old infants watch while an adult performed an unsuccessful action. The reasoning is that if the infant later imitates what the model actually did, even though it didn't work, then all that might be involved is a simple, straightforward type of copying. But if the infant tried to imitate the "intended" act, then we might assume that a correct inference has been made about the actor's intentions. In one study, for example, the experimenter seems to be trying to pull apart a small dumbbell, but fails. In the testing phase, infants typically try to accomplish the inferred intention rather than imitate the model's actions literally. When they are given oversized plastic dumbbells that they can't possibly hold in the same way as the model, they make no attempt to mimic the model directly. Instead, they try novel solutions, like placing the dumbbell on a table and pulling on the other end with both hands.
Achievements of Imitation in Infancy
Studies of imitation among infants show a gradual progression from being able to imitate simple body movements to imitating actions performed with objects, and, finally, to imitation based on being able to correctly infer the intentions of the model (Rao, Shon, & Meltzoff, 2007).
Infant imitation leads to at least three different kinds of learning. First, infants learn about places by following people around, in much the same way that young kittens and other animals learn about places by following their mothers and siblings. Second, through imitation infants learn certain social behaviors, such as sharing toys. After playing "give and take" games with parents, infants are more likely to want to give toys to others. And third, infants learn new social behaviors by observing them in others. Among the most important of new behaviors that they learn at least partly through imitation are those that have to do with speaking and understanding a language.
Adaptation and Information Processing in Piaget's Theory
In the beginning, Piaget tells us, the infant's world is a world of the here and now. Because the infant has no object concept, the world makes sense only when the infant looks at it, hears it, touches it, smells it, or tastes it. Nor do infants have concepts in the sense that we think of them: They have no store of memories or hopes or dreams, no fund of information with which to think. But what neonates have are the sensory systems and the cognitive inclinations that make them highly effective, information-processing organisms. They continually seek out and respond to stimulation and, in the process, gradually build up a repertoire of behaviors and capabilities.
At first, infants' behaviors are limited mainly to the simple reflexes with which they are born; but in time these behaviors become more elaborate and more coordinated with one another. The process by which this occurs is adaptation, and the complementary processes that make adaptation possible are assimilation and accommodation (see Chapter 2).
To review briefly, assimilation and accommodation are highly active processes whereby an individual searches out, selects, and responds to information, the end result of which is the actual construction of knowledge. Imagine, for example, an 18-month-old walking on a beach, stooping now and again to pick up pebbles and toss them into the water. In Piaget's view, there is a schema (plural schemata) involved here—a sort of mental or cognitive representation—that corresponds to the child's knowledge of the suitability of pebbles as objects to be thrown in the water, as well as other schemata that concern the activities involved in bending, retrieving, and throwing. The pebbles are, in a sense, being assimilated to appropriate schemata; they are understood and used in terms of the child's previous knowledge.
magine, now, that the child bends to retrieve another pebble but finds, instead, that she has picked up a piece of driftwood. The wood is clearly not a pebble, and perhaps it should not be responded to in the same way. But still, why not? The "throwing things on the big waves" schema is readily available and momentarily preferred, and so the wood too is assimilated to the throwing schema. The child tries to hurl it toward the water, but the new object's heaviness is surprising, the child's throwing motion inadequate, and the driftwood fails to reach the water. Now, when she picks it up again, she doesn't hurl it in quite the same way. She holds it in two hands, grasps it tightly with her tiny fingers, and pushes hard with her little legs as she throws. In Piaget's terms, she has accommodated to the characteristics of this object that make it different from the pebbles she has been throwing.
To simplify these sometimes difficult concepts, to assimilate is to respond in terms of preexisting information. It often involves ignoring some aspects of the situation to make it conform to aspects of the mental system. In contrast, to accommodate is to respond to external characteristics and to make changes in the mental system as a result. And one of the governing principles that guides mental activity, says Piaget, is a tendency to find a balance between accommodation and assimilation. This tendency is labeled equilibration.
At one extreme, if an infant always assimilated but never accommodated, there would be no change in schemata (mental structure), no change in behavior, and, by definition, no learning. Everything would be assimilated to the sucking schema, the grasping schema, the looking schema (that is, everything would be sucked or grasped or simply looked at). Such a state of disequilibrium would result in little adaptation and little cognitive growth.
At the other extreme, if everything were accommodated to and not assimilated, schemata—and behavior—would be in a constant state of flux: First the nipple would be sucked, then it would be chewed, now pinched, then swatted. Again, such an extreme state of disequilibrium would result in little adaptation.
Equilibration, says Piaget, is one of the four forces that shape development (Piaget, 1961). Another is maturation, a sort of biologically determined unfolding of potential. Maturation—or biology—does not determine cognitive growth but is related to its unfolding. A third factor is active experience, a child's interaction with the world. A fourth factor is social interaction, which helps the child develop ideas about things, about people, and about the self. These four factors—active experience, maturation, equilibration, and social interaction—are the cornerstones of Piaget's basic theory.
Sensorimotor Development
Piaget believed that children's understanding of the world throughout most of infancy is determined by the activities they can perform on it and by their perceptions of it—hence his label sensorimotor development for this first stage, which spans infancy. (Figure 2.9, Chapter 2, summarizes all Piaget's stages.)
Sensorimotor development, says Piaget (1961), can be described in terms of six substages. During the first, which lasts about a month, infants spend much of their waking time exercising the abilities with which they are born (sucking, looking, and crying, for example). By the end of the first month, infants are quite proficient at these activities, but they have trouble putting different actions together (coordinating their behavior) to obtain a goal. When shown a shiny new bauble, an infant stares at it intently but cannot reach toward it.
The second sensorimotor stage, lasting from one to four months, is marked by highly repetitive behaviors (thumb sucking, for example) called primary circular reactions. These are behaviors that are initially reflexive and that serve as stimuli for their own repetition. For example, if an infant accidentally gets a hand or a finger into the mouth, this triggers the sucking response, which results in the sensation of the hand in the mouth. That sensation leads to a repetition of the response, which leads to a repetition of the sensation, which leads to a repetition of the response. This circle of action is called primary because it involves the infant's own body.
Between ages 4 and 8 months, secondary circular reactions appear. Like primary circular reactions, they are circular because the responses stimulate their own repetition; but because they deal with objects in the environment rather than only with the infant's body, they are called secondary. Six-month-old infants engage in many secondary circular reactions. They accidentally do something that is interesting or amusing and then repeat it again and again. By kicking, Piaget's infant son caused a row of dolls dangling above his bassinet to dance. The boy stopped and watched the dolls. Eventually, he repeated the kicking, perhaps not intending to make the dolls move, but probably because they had stopped moving and no longer attracted his attention. As he kicked, the dolls moved again, and again he paused to look at them. In a very short time he was repeating the behavior over and over—a circular reaction. This behavior, which Piaget described as "behavior designed to make interesting sights and sounds last," is especially important because it signals the beginning of intention.
The development of intention becomes even more apparent when, in the fourth substage (8 to 12 months), infants acquire the ability to coordinate previously unrelated behaviors to achieve some desired goal. They can now look at an object, reach for it, grasp it, and bring it to the mouth with the intention of sucking it.
In the fifth substage (12 to 18 months), infants begin to modify their repetitive behaviors deliberately to see what the effects will be. These tertiary circular reactions are evident in exploratory behaviors, in which an infant takes a piece of spaghetti, presses it to the floor, breaks it, picks up the largest piece, breaks it again, and repeats the process a number of times. The most important feature of tertiary circular reactions is that they are repetitive behaviors deliberately undertaken to see what their effects will be; that is, they are explorations.
Toward the end of the sensorimotor period, infants are well on their way to making a transition from what has been an action-based (hence sensorimotor) intelligence to a progressively more cognitive (symbolic or representational) intelligence. Infants can now represent objects and events mentally. They can even occasionally combine these representations to arrive at mental solutions for problems, and they are now able to anticipate the consequences of many of their activities before actually executing them. In Piaget's terms, it is as though the child can now begin to internalize (represent mentally) actions and their consequences without having to carry them out. We do this all the time. We call it thinking or information processing. One of the advantages of Piaget's use of the expression internalizing actions is that it draws attention to how closely the infant's (and the child's) thinking is linked to physical action, emphasizing how important early experiences are in the development of thought.
The process of internalizing actions is well illustrated by Piaget's account of his daughter's behavior when she was given a partly open matchbox containing a small thimble. Because the opening was too small for her to withdraw the thimble, she had to open the box first. A younger infant would simply grope at the box, attempting clumsily to remove the thimble. But Piaget's daughter, then 22 months, appeared to be considering the problem. She opened and closed her mouth repeatedly as if displaying internal thought processes—as if, in a sense, imagining (and unconsciously illustrating with her mouth) the opening and closing of the box. Finally, she placed her finger directly into the box's partial opening, opened it, and removed the thimble.
5.6 Early Language Development
Piaget's 22-month-old daughter could not only solve the opening-the-box problem: If she so wished, she could tell everybody about her triumph! And she could now do so not only by jumping up and down and shrieking, but also by using actual words.
Despite its tremendous power, language is not always essential for communication (the transmission of messages)—as an infant jumping up and down and shrieking, or a dog growling, clearly demonstrate. Language is the use of arbitrary sounds (or, in some cases, gestures, as in American Sign Language (ASL)), in purposeful ways to convey different meanings.
The Prespeech Stage of Language Development
Infants' first communication system is not a language so much as a system of gestures and sounds. To master a language, infants needs to learn not only how to produce sounds and gestures, but also how to take turns, and how to discriminate sounds.
Turn Taking: The Beginnings of Verbal Communication
The ability to use and to understand words grows out of the interactions that take place between infants and their caregivers, siblings, and other people. One of the first things the infant learns through this support system is how to take turns—an achievement that is basic to adult conversation.
Amazingly, infants seem to have a relatively sophisticated awareness of turn-taking signals at very young ages. In one investigation, Elias and Broerse (1996) looked at interactions between 48 mothers and their 3- to 24-month-old infants. They found a remarkable tendency for mother-infant pairs to interact in alternating fashion.
Using Gestures
Even before they have begun to use words, infants have typically developed a repertoire of gestures that are clearly meaningful for both infants and caregivers. Many of these are associated with gazing, which is used to direct people's attention and to indicate desired objects. Also, very much like adults, infants often follow another person's gaze.
During the first two years, infants develop a large number of different gestures that they can use in place of, or in combination with, words. Interestingly, bilingual children tend to use more gestures when speaking their dominant rather than their second language (Laurent, Nicoladis, & Marentette, 2010). Also interesting is the finding that older adults who are beginning to lose some of their language skills often resort to an increasing use of gestures (Goldin-Meadow & Iverson, 2010).
Among gestures commonly used by infants, pointing is one of the last to develop (at around ages 12 to 14 months) (Masur, 1993). Other gestures, such as offering objects and reaching for things, are relatively common by the age of 9 months. By the age of 15 months, infants can direct their gazing and their pointing in different directions at the same time. This is evident, for example, when a 16-month-old points to the plate he has just thrown on the floor and looks at his mother at the same time. Being able to refer to two objects at once is a remarkable new achievement.
The use of gestures by caregivers plays an important role in the infant's early learning of language. For example, de Villiers Rader and Zukow-Goldring (2010) found that when parents used dynamic gestures synchronized with both the sight of an object and the word associated with it, infants paid more attention to the object and learned the word better.
Discriminating Sounds
Communicating through language depends on being able to discriminate sounds as well as produce them. Auditory speech, Werker and Tees (1999) point out, is far more complex than written language. What you are reading at this moment consists of words that are separated by spaces and that are organized into sentence-sized chunks whose meaning is signaled with punctuation, capitalization, boldfacing, and italicizing. Furthermore, you can reread any part of it at your whim. Not so with speech. Examination of acoustic waves shows no regular breaks between words, and no division between sentences or paragraphs. Yet infants are soon able to discriminate individual sounds. And before a year has passed, they have even begun to assign them meanings.
Sound Production
Discriminating among sounds is one aspect of early language learning; producing intended sounds is the other. It starts with the crying, cooing, and eventual babbling of the infant. Eventually it progresses to a word, and then a sentence, a paragraph, a chapter, a book . . .
Infants' first sounds are haphazard and varied, but they soon gain control over their sound-producing apparatus. Also, they discover that producing sounds is "fun," and contented infants may spend hours in solitary babbling without any prompting. As a result, by the age of 10 months, most children babble clearly, systematically, and repetitively. Children who have mild hearing problems reach this stage later; if their hearing problems are serious enough, they do not progress through the normal stages of babbling and language learning (Bass-Ringdahl, 2010).
The First Word
At around 1, but sometimes much earlier or much later, the first word appears—not surprisingly, often "mama" or "papa"—although it is seldom easy to determine when infants say their first word. Often, the first consistent sound made repeatedly by an infant is not a word but has clear meaning. These sounds are referred to as protowords.
Holophrases also appear early in the speech stage of language learning. Unlike protowords, these are real words rather than just sounds, and their meaning is often complex and elaborate. The holophrase "up" allows an 18-month-old to convey the meaning "If you don't pick me up I will do something very annoying," without having to use more than one word.
The appearance of the first word is rapidly followed by new words that the child practices incessantly. Most of an English-speaking child's first words are nouns—simple names for simple things, usually objects or people that are part of the here and now: "dog," "mama," "banket" (blanket), or "yefant" (elephant). Verbs, adjectives, adverbs, and prepositions are acquired primarily in the order listed here, with the greatest difficulty usually being the use of pronouns, especially the pronoun "I" (Boyd, 1976).
Two-Word Sentences
By the age of 18 months, most infants have begun to make two-word sentences—often grammatically incorrect but always meaningful. There is also normally a tremendous spurt in vocabulary, which appears to be common to all cultures. Whereas learning the first hundred words might take several months, learning the next hundred might only take a few weeks (Yu, 2008). This process is called fast mapping. (See In the Classroom, I Should Like to . . .)
Multiple-Word Sentences
Multiple-word sentences typically appear shortly after the age of 2. Early preschool speech is often telegraphic speech— so-called because it eliminates many parts of speech while still managing to convey meanings. And although it is often grammatically incorrect, it includes complex grammatical variations to express different meanings. By the late preschool years, it has become adultlike (Table 5.4).
Three Explanations for Language Learning
We know that learning a language requires certain biological characteristics—vocal apparatus, hearing, the brain. We know too that it is highly dependent on experiences with others who have already acquired a language. The story of Genie, described in Chapter 3, makes that clear. Genie was rescued at age 13, at which time she had a vocabulary of about 20 words—mostly short, negative phrases such as "stop it," and "no more." In addition, she had developed a limited repertoire of gestures consisting mostly of spitting and clawing. But most of the time, she was silent—evidence, says Rymer (1994), that she had not been exposed to language during critical periods of her life.
In spite of being rescued at age 13, and even though dedicated therapists worked with her over a long period, Genie's language development reached only a very primitive level, as shown in this excerpt of a conversation she had with one of her foster mothers, Marilyn Rigler:
Marilyn Rigler: Do you remember what it was like when you lived at home? What were you sitting on when you ate the cereal?
Genie: In the pot.
Marilyn Rigler: In the potty chair.
Genie: In the potty chair.
Marilyn Rigler: Where did you stay when you lived at home? Where did you live? Where did you sleep?
Genie: Potty chair.
Marilyn Rigler: You slept in the potty chair?
Genie: Mmm-hmm. Potty chair. (Secrets of the wild child, 1997)
Language, some theorists insist, is a sort of special gift given only to humans and not other animals; its acquisition can only be explained by reference to things extraordinary and mysterious. Deacon (1997) labels such explanations hopeful monsters; other theorists refer to them as a form of nativism (MacWhinney, 1998).
The best known of the hopeful monster or nativistic theories of language development is that of the linguist, Noam Chomsky (1972). Chomsky argues that because children learn language, and especially grammar, so rapidly, and because they make so few of the errors that one might expect them to make if they had to learn each rule and each exception individually, they must be born with a powerful biological predisposition to learn language. This predisposition, Chomsky speculates, takes the form of neurological pre-wiring in the brain, corresponding to language and grammar, which he labels the language acquisition device (LAD).
Another explanation views language acquisition as the end result of a learning process highly dependent on interaction with other speakers. This explanation sees language as something that emerges gradually and is labeled emergentism (MacWhinney, 1998). Emergent explanations are often based on the principles of reinforcement in operant conditioning (described in Chapter 2). They might argue, for example, that while babbling, the infant emits wordlike sounds that tend to be reinforced by adults.
A third explanation is the interactionist theory of language learning. It is both a biological and social explanation—biological in that it holds that children are born with a powerful, innate predisposition to learn language, and social in that the learning of language involves the fundamentally social act of sharing symbols and meanings with others. Vygotsky is closely associated with the interactionist view.
The most popular current explanations are basically interactionist. Though they recognize the child's biological predispositions, they tend to focus on the mental and social processes involved in language learning.
5.7 From Sensation to Representation
The word infant derives from the Latin infans, meaning "without speech." And, in fact, throughout much of the period we call infancy, a child is without speech. As noted earlier, the world of the newborn is a world of the here and now, a world that cannot be represented symbolically but can only be acted on and felt—in short, a sensorimotor world.
