Infant and Toddler Parent Handout week 3

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CHAPTER 6 COGNITIVE DEVELOPMENT IN INFANCY AND TODDLERHOOD

The Birds Are Back

Lene Margrethe Linnerud, 12 years, Norway

Children greet a returning flock of birds while their baby sibling plays nearby. In Chapter 6, you will see that a stimulating environment and the guidance of more mature members of their culture ensure that infants’ and toddlers’ cognition will develop at its best.

Reprinted with permission from The International Museum of Children’s Art, Oslo, Norway

WHAT’S AHEAD IN CHAPTER 6

6.1 Piaget’s Cognitive-Developmental Theory

Piaget’s Ideas About Cognitive Change • The Sensorimotor Stage • Follow-Up Research on Infant Cognitive Development • Evaluation of the Sensorimotor Stage

■ Social Issues: Education: Baby Learning from Screen Media: The Video Deficit Effect

6.2 Information Processing

Assumptions of the Information-Processing Perspective • Attention • Memory • Categorization • Evaluation of Information-Processing Findings

■ Biology and Environment: Infantile Amnesia

6.3 The Social Context of Early Cognitive Development

■ Cultural Influences: Social Origins of Make-Believe Play

6.4 Individual Differences in Early Mental Development

Infant and Toddler Intelligence Tests • Early Environment and Mental Development • Early Intervention for At-Risk Infants and Toddlers

6.5 Language Development

Theories of Language Development • Getting Ready to Talk • First Words • The Two-Word Utterance Phase • Individual and Cultural Differences • Supporting Early Language Development

■ Biology and Environment: Thiamine Deficiency in the First Year and Later Language Impairment

When 19-month-olds Caitlin and Grace and 21-month-old Timmy gathered at Ginette’s child-care home, the playroom was alive with activity. The three spirited explorers were bent on discovery. Grace dropped shapes through holes in a plastic box that Ginette held and adjusted so the more difficult ones would fall smoothly into place. Once a few shapes were inside, Grace grabbed the box and shook it, squealing with delight as the lid fell open and the shapes scattered around her. The clatter attracted Timmy, who picked up a shape, carried it to the railing at the top of the basement steps, dropped it overboard, and then followed it with a teddy bear, a ball, his shoe, and a spoon.

Meanwhile, Caitlin pulled open a drawer, unloaded a set of wooden bowls, stacked them in a pile, knocked it over, and then banged two bowls together. With each action, the children seemed to be asking, “How do things work? What makes interesting events happen? Which ones can I control?”

As the toddlers experimented, I could see the beginnings of spoken language—a whole new way of influencing the world. “Baw!” Caitlin exclaimed as Timmy tossed the bright red ball down the basement steps. “Bye-bye,” Grace chimed in, waving as the ball rolled out of sight. Later that day, Grace revealed that she could pretend. “Night-night,” she said, hugging her teddy bear, putting her head down, briefly closing her eyes, then “awakening” and exclaiming, “No more nap!”

Over the first two years, the small, reflexive newborn baby becomes a self-assertive, purposeful being who solves simple problems and starts to master the most amazing human ability: language. Parents wonder, “How does all this happen so quickly?” This question has also captivated researchers, yielding a wealth of findings along with vigorous debate over how to explain the astonishing pace of infant and toddler cognitive development.

In this chapter, we take up three perspectives: Piaget’s cognitive-developmental theory, information processing, and Vygotsky’s sociocultural theory. We also consider the usefulness of tests that measure infants’ and toddlers’ intellectual progress. Finally, we look at the dawning of language. We will see how toddlers’ first words build on early cognitive achievements and how, very soon, new words and expressions greatly increase the speed and flexibility of thinking. Throughout development, cognition and language mutually support each other. ■

6.1 PIAGET’S COGNITIVE-DEVELOPMENTAL THEORY

Swiss theorist Jean Piaget inspired a vision of children as busy, motivated explorers whose thinking develops as they act directly on the environment. Influenced by his background in biology, Piaget believed that the child’s mind forms and modifies psychological structures so they achieve a better fit with external reality. Recall from Chapter 1 that in Piaget’s theory, children move through four stages between infancy and adolescence. During these stages, Piaget claimed, all aspects of cognition develop in an integrated fashion, changing in a similar way at about the same time.

Piaget’s sensorimotor stage spans the first two years of life. Piaget believed that infants and toddlers “think” with their eyes, ears, hands, and other sensorimotor equipment. They cannot yet carry out many activities inside their heads. But by the end of toddlerhood, children can solve everyday practical problems and represent their experiences in speech, gesture, and play. To appreciate Piaget’s view of how these vast changes take place, let’s consider some important concepts.

6.1.1 Piaget’s Ideas About Cognitive Change

6.1a Explain how, in Piaget’s theory, schemes change over the course of development.

6.1b Describe major cognitive attainments of the sensorimotor stage.

6.1c Explain the implications of follow-up research on infant cognitive development for the accuracy of Piaget’s sensorimotor stage.

According to Piaget, specific psychological structures—organized ways of making sense of experience called schemes—change with age. At first, schemes are sensorimotor action patterns. For example, at 6 months, Timmy dropped objects in a fairly rigid way, simply letting go of a rattle or teething ring and watching with interest. By 18 months, his “dropping scheme” had become deliberate and creative. In tossing objects down the basement stairs, he threw some in the air, bounced others off walls, released some gently and others forcefully. Soon, instead of just acting on objects, he will show evidence of thinking before he acts. For Piaget, this change marks the transition from sensorimotor to preoperational thought.

In Piaget’s theory, two processes, adaptation and organization, account for changes in schemes.

Adaptation

The next time you have a chance, notice how infants and toddlers tirelessly repeat actions that lead to interesting effects. Adaptation involves building schemes through direct interaction with the environment. It consists of two complementary activities: assimilation and accommodation. During assimilation, we use our current schemes to interpret the external world. For example, when Timmy dropped objects, he was assimilating them to his sensorimotor “dropping scheme.” In accommodation, we create new schemes or adjust old ones after noticing that our current ways of thinking do not capture the environment completely. When Timmy dropped objects in different ways, he modified his dropping scheme to take account of the varied properties of objects.

According to Piaget, the balance between assimilation and accommodation varies over time. When children are not changing much, they assimilate more than they accommodate—a steady, comfortable state that Piaget called cognitive equilibrium. During times of rapid cognitive change, children are in a state of disequilibrium, or cognitive discomfort. Realizing that new information does not match their current schemes, they shift from assimilation to accommodation. After modifying their schemes, they move back toward assimilation, exercising their newly changed structures until they are ready to be modified again.

Each time this back-and-forth movement between equilibrium and disequilibrium occurs, more effective schemes are produced. Because the times of greatest accommodation are the earliest ones, the sensorimotor stage is Piaget’s most complex period of development.

In Piaget’s theory, first schemes are sensorimotor action patterns. As this 12-month-old experiments with his dropping scheme, his behavior becomes more deliberate and varied.

Organization

Schemes also change through organization, a process that occurs internally, apart from direct contact with the environment. Once children form new schemes, they rearrange them, linking them with other schemes to create a strongly interconnected cognitive system. For example, eventually Timmy will relate “dropping” to “throwing” and to his developing understanding of “nearness” and “farness.” According to Piaget, schemes truly reach equilibrium when they become part of a broad network of structures that can be jointly applied to the surrounding world (Piaget, 1936/1952).

In the following sections, we will first describe infant development as Piaget saw it, noting research that supports his observations. Then we will consider evidence demonstrating that in some ways, babies’ cognitive competence is more advanced than Piaget believed.

6.1.2 The Sensorimotor Stage

The difference between the newborn baby and the 2-year-old child is so vast that Piaget divided the sensorimotor stage into six substages, summarized in Table 6.1. Piaget based this sequence on a very small sample: He observed his own three children carefully and also presented them with everyday problems (such as hidden objects) that helped reveal their understanding of the world.

Table 6.1 Summary of Piaget’s Sensorimotor Stage

Sensorimotor Substage

Typical Adaptive Behaviors

1. Reflexive schemes (birth–1 month)

Newborn reflexes (see Chapter 4, page 134)

2. Primary circular reactions (1–4 months)

Simple motor habits centered around the infant’s own body; limited anticipation of events

3. Secondary circular reactions (4–8 months)

Actions aimed at repeating interesting effects in the surrounding world; imitation of familiar behaviors

4. Coordination of secondary circular reactions (8–12 months)

Intentional, or goal-directed, behavior; ability to find a hidden object in the first location in which it is hidden (object permanence); improved anticipation of events; imitation of behaviors slightly different from those the infant usually performs

5. Tertiary circular reactions (12–18 months)

Exploration of the properties of objects by acting on them in novel ways; imitation of novel behaviors; ability to search in several locations for a hidden object (accurate A–B search)

6. Mental representation (18 months–2 years)

Internal depictions of objects and events, as indicated by sudden solutions to problems; ability to find an object that has been moved while out of sight (invisible displacement); deferred imitation; and make-believe play

According to Piaget, at birth infants know so little that they cannot explore purposefully. The circular reaction provides a special means of adapting their first schemes. It involves stumbling onto a new experience caused by the baby’s own motor activity. The reaction is “circular” because, as the infant tries to repeat the event again and again, a sensorimotor response that originally occurred by chance strengthens into a new scheme. Consider Caitlin, who at age 2 months accidentally made a smacking sound after a feeding. Intrigued, she tried to repeat it until, after a few days, she became quite expert at smacking her lips.

This 3-month-old repeats a newly discovered action—sucking her toes—in a primary circular reaction that helps her gain voluntary control over her behavior.

The circular reaction initially centers on the infant’s own body and later turns outward, toward manipulation of objects. In the second year, it becomes experimental and creative, aimed at producing novel outcomes. Infants’ difficulty stopping themselves from repeating new and interesting behaviors may underlie the circular reaction. This immaturity in inhibition seems to be adaptive, helping to ensure that new skills will not be interrupted before they strengthen (Carey & Markman, 1999). Piaget considered revisions in the circular reaction so important that, as Table 6.1 shows, he named the sensorimotor substages after them.

When this 4-month-old accidentally hits a toy hung in front of her, her action causes it to swing. Using the secondary circular reaction, she tries to recapture this interesting effect. In the process, she forms a new “hitting scheme.”

Repeating Chance Behaviors

Piaget saw newborn reflexes as the building blocks of sensorimotor intelligence. In Substage 1, babies suck, grasp, and look in much the same way, no matter what experiences they encounter. Around 1 month, as they enter Substage 2, they start to gain voluntary control over their actions through the primary circular reaction, by repeating chance behaviors largely motivated by basic needs. This leads to some simple motor habits, such as sucking their fists or thumbs. Babies of this substage also begin to vary their behavior in response to environmental demands. For example, they open their mouths differently for a nipple than for a spoon. And they start to anticipate events. On awaking from a nap hungry, 3-month-old Timmy would stop crying as soon as Vanessa entered the room—a sign that feeding time was near.

During Substage 3, from 4 to 8 months, infants sit up and reach for and manipulate objects. These motor attainments strengthen the secondary circular reaction, through which babies try to repeat interesting events in the surrounding environment that are caused by their own actions. For example, 4-month-old Caitlin accidentally knocked a toy hung in front of her, producing a fascinating swinging motion. Over the next three days, Caitlin tried to repeat this effect, gradually forming a new “hitting” scheme.

Improved control over their own behavior permits infants to imitate others’ behavior more effectively. Piaget noted, however, that 4- to 8-month-olds cannot adapt flexibly and quickly enough to imitate novel behaviors. Although they enjoy watching an adult demonstrate a game of pat-a-cake, they are not yet able to participate.

Intentional Behavior

In Substage 4, 8- to 12-month-olds combine schemes into new, more complex action sequences. As a result, actions that lead to new schemes no longer have a random, hit-or-miss quality—accidentally bringing the thumb to the mouth or happening to hit the toy. Instead, 8- to 12-month-olds can engage in intentional, or goal-directed, behavior, coordinating schemes deliberately to solve simple problems. Consider Piaget’s famous object-hiding task, in which he shows the baby an attractive toy and then hides it behind his hand or under a cover. Infants of this substage can find the object by coordinating two schemes—”pushing” aside the obstacle and “grasping” the toy. Piaget regarded these means–end action sequences as the foundation for all problem solving.

Retrieving hidden objects reveals that infants have begun to master object permanence, the understanding that objects continue to exist when they are out of sight. But this awareness is not yet complete. Babies make the A-not-B search error: If they reach several times for an object at a first hiding place (A) and then see it moved to a second (B) hiding place, they still search for it in the first hiding place (A). Consequently, Piaget concluded that they do not have a clear image of the object as persisting when hidden from view.

Infants in Substage 4, who can better anticipate events, sometimes use their capacity for intentional behavior to try to change those events. At 10 months, Timmy crawled after Vanessa when she put on her coat, whimpering to keep her from leaving. Also, babies can now imitate behaviors slightly different from those they usually perform. After watching someone else, they try to stir with a spoon, push a toy car, or drop raisins into a cup (Piaget, 1945/1951).

In Substage 5, from 12 to 18 months, the tertiary circular reaction emerges, in which toddlers repeat behaviors with variation. Recall how Timmy dropped objects over the basement steps, trying this action, then that, then another. This deliberately exploratory approach makes 12- to 18-month-olds better problem solvers. For example, Grace figured out how to fit a shape through a hole in a container by turning and twisting it until it fell through and how to use a stick to get an out-of-reach toy. According to Piaget, this capacity to experiment leads toddlers to look for a hidden toy in several locations, displaying an accurate A–B search. Their more flexible action patterns also permit them to imitate many more behaviors, such as stacking blocks, scribbling on paper, and making funny faces.

To find the toy hidden inside the pot, a 10-month-old engages in intentional, goal-directed behavior—the basis for all problem solving.

Using a tertiary circular reaction, this baby twists, turns, and pushes until a block fits through its matching hole in a shape sorter. Between 12 and 18 months, toddlers take a deliberately experimental approach to problem solving.

Mental Representation

Substage 6 brings the ability to create mental representations—internal depictions of information that the mind can manipulate. Our most powerful mental representations are of two kinds: (1) images—mental pictures of objects, people, and spaces; and (2) concepts—categories in which similar objects or events are grouped together. We use a mental image to retrace our steps when we’ve misplaced something or to imitate someone’s behavior long after observing it. By thinking in concepts and labeling them (for example, “ball” for all rounded, movable objects used in play), we become more efficient thinkers, organizing our diverse experiences into meaningful, manageable, and memorable units.

Piaget noted that 18- to 24-month-olds arrive at solutions suddenly rather than through trial-and-error behavior. In doing so, they seem to experiment with actions inside their heads—evidence that they can mentally represent their experiences. For example, at 19 months, Grace—after bumping her new push toy against a wall—paused for a moment as if to “think,” and then immediately turned the toy in a new direction.

Representation enables older toddlers to solve advanced object permanence problems involving invisible displacement—finding a toy moved while out of sight, such as into a small box while under a cover. It also permits deferred imitation—the ability to remember and copy the behavior of models who are not present. And it makes possible make-believe play, in which children act out everyday and imaginary activities. As the sensorimotor stage draws to a close, mental symbols have become major instruments of thinking.

The capacity for mental representation enables this 20-month-old to engage in first acts of make-believe.

6.1.3 Follow-Up Research on Infant Cognitive Development

Many studies suggest that infants display a wide array of understandings earlier than Piaget believed. Recall the operant conditioning research reviewed in Chapter 5, in which newborns sucked vigorously on a nipple to gain access to interesting sights and sounds. This behavior, which closely resembles Piaget’s secondary circular reaction, shows that babies try to explore and control the external world long before 4 to 8 months. In fact, they do so as soon as they are born.

To discover what infants know about hidden objects and other aspects of physical reality, researchers often use the violation-of-expectation method. They may habituate babies to a physical event (expose them to the event until their looking declines) to familiarize them with a situation in which their knowledge will be tested. Or they may simply show babies an expected event (one that is consistent with reality) and an unexpected event (a variation of the first event that violates reality). Heightened attention to the unexpected event suggests that the infant is “surprised” by a deviation from physical reality and, therefore, is aware of that aspect of the physical world.

The violation-of-expectation method is controversial. Some researchers believe that it indicates limited, implicit (nonconscious) awareness of physical events—not the full-blown, conscious understanding that was Piaget’s focus in requiring infants to act on their surroundings, as in searching for hidden objects (Campos et al., 2008). Others maintain that the method reveals only babies’ perceptual preference for novelty, not their knowledge of the physical world. According to these researchers, infants may look longer at the novel (unexpected) event simply because it requires more time to make sense of than the expected event (Dunn & Bremner, 2017; Bremner, Slater, & Johnson, 2015). Let’s examine this debate in light of recent evidence.

Object Permanence

In a series of studies using the violation-of-expectation method, Renée Baillargeon and her collaborators claimed to have found evidence for object permanence in the first few months of life. Figure 6.1 on page 202 describes and illustrates one of these studies, in which infants exposed to both an expected and an unexpected object-hiding event looked longer at the unexpected event (Aguiar & Baillargeon, 2002; Baillargeon & DeVos, 1991).

Additional violation-of-expectation studies yielded similar results, suggesting that infants look longer at a wide variety of unexpected events involving hidden objects (Wang, Baillargeon, & Paterson, 2005). Still, several researchers using similar procedures failed to confirm some of Baillargeon’s findings (Cohen & Marks, 2002; Schöner & Thelen, 2006; Sirois & Jackson, 2012). And, as previously noted, critics question what babies’ looking preferences tell us about what they actually understand.

Another type of looking behavior suggests that young infants are aware that objects persist when out of view. Four- and 5-month-olds will track a ball’s path of movement as it disappears and reappears from behind a barrier, even gazing ahead to where they expect it to emerge. As further support for such awareness, 5- to 9-month-olds more often engaged in such predictive tracking when a ball viewed on a computer screen gradually rolled behind a barrier than when it disappeared instantaneously or imploded (rapidly decreased in size) at the barrier’s edge (Bertenthal, Gredebäck, & Boyer, 2013; Bertenthal, Longo, & Kenny, 2007). With age, babies are more likely to fixate on the predicted place of the ball’s reappearance and wait for it—evidence of an increasingly secure grasp of object permanence.

If young infants do have some notion of object permanence, how do we explain Piaget’s finding that even infants capable of reaching do not try to search for hidden objects before 8 months of age? Compared with looking reactions in violation-of-expectation tasks, searching for a hidden object is far more cognitively demanding: The baby must figure out where the hidden object is. Consistent with this idea, infants solve some object-hiding tasks before others. For example, 10-month-olds search for an object placed on a table and covered by a cloth before they search for an object that a hand deposits under a cloth. Experience with partially hidden objects—common in infants’ everyday lives—may help them grasp that the cloth-covered object has not been replaced by the cloth but, rather, continues to exist and can be retrieved. In the second, more difficult task, infants seem to expect the object to reappear in the hand from which it initially disappeared (Moore & Meltzoff, 1999, 2008). Not until 14 months can most babies infer that the hand deposited the object under the cloth.

Figure 6.1 Testing young infants for awareness of object permanence using the violation-of-expectation method. (a) First, infants were habituated to two events: a short carrot and a tall carrot moving behind a yellow screen on alternate trials. Next, the researchers presented two test events. The color of the screen was changed to help infants notice its window. (b) In the expected event, the carrot shorter than the window’s lower edge moved behind the blue screen and reappeared on the other side. (c) In the unexpected event, the carrot taller than the window’s lower edge moved behind the screen and did not appear in the window, but then emerged intact on the other side. Infants as young as 2½ to 3½ months looked longer at the unexpected event, suggesting that they had some awareness of object permanence. Adapted from R. Baillargeon & J. DeVos, 1991, “Object Permanence in Young Infants: Further Evidence,” Child Development, 62, p. 1230.

Searching for Objects Hidden in More Than One Location

Once 8- to 12-month-olds search for hidden objects, they make the A-not-B search error. Some research suggests that they search at A (where they found the object on previous reaches) instead of B (its most recent location) because they have trouble inhibiting a previously rewarded motor response (Diamond, Cruttenden, & Neiderman, 1994; Johansson, Forssman, & Bohlin, 2014). Another possibility is that after finding the object several times at A, babies do not attend closely when it is hidden at B (Ruffman & Langman, 2002).

A more comprehensive explanation is that a complex, dynamic system of factors—having built a habit of reaching toward A, continuing to look at A, having the hiding place at B appear similar to the one at A, and maintaining a constant body posture—increases the chances that the baby will make the A-not-B search error. Disrupting any one of these factors induces 10-month-olds to think more flexibly, increasing their accurate searching at B (Thelen et al., 2001). In addition, older infants are still perfecting reaching and grasping (see Chapter 5) (Berger, 2010). If these motor skills are challenging, babies have little attention left to focus on inhibiting their habitual reach toward A.

Around 12 months, infants respond to an adult’s verbal prompts to search for a hidden object (“Find the ball!”) by looking at and gesturing toward where they last saw it (Saylor, Ganea, & Vásquez, 2011). But they do so only if the object is easily accessible. If an adult places the container in which the object is hidden in an inaccessible location (on an out-of-reach shelf), 12-month-olds won’t look, point, or move toward the container (Osina, Saylor, & Ganea, 2017). Their difficulty is not that they have forgotten about the hidden object, because if the adult moves the container to an accessible location, 12-month-olds promptly recover the object. Rather, making a hidden object inaccessible seems to inhibit their willingness to search. By 16 months, searching is no longer affected by object accessibility. As toddlers grow taller and walk more securely, they may modify their representations of hidden objects, viewing those beyond their immediate reach as retrievable.

In sum, mastery of object permanence is a gradual achievement. Babies’ understanding becomes increasingly complex with age: They must perceive an object’s identity by integrating feature and movement information (see pages 190–191 in Chapter 5), distinguish the object from the barrier concealing it and the surface on which it rests, keep track of the object’s whereabouts, and use this knowledge to obtain the object (Bremner, Slater, & Johnson, 2015). A wide variety of experiences perceiving, remembering, acting on, and communicating about objects undoubtedly contributes to the emergence of these capabilities.

Look and Listen

Using an attractive toy and cloth, try several object-hiding tasks with 8- to 14-month-olds. Is their search behavior consistent with research findings?

Mental Representation

In Piaget’s theory, before about 18 months, infants are unable to mentally represent experience. Yet 8- to 10-month-olds’ recall the location of hidden objects after delays of more than a minute and 14-month-olds’ after delays of a day or more, clearly indicating that babies construct mental representations of objects and their whereabouts (McDonough, 1999; Moore & Meltzoff, 2004). In studies of deferred imitation and problem solving, representational thought is evident even earlier. And toddlers make impressive strides in symbolic understanding, as their grasp of words and photos reveals.

Deferred and Inferred Imitation

Piaget studied imitation by noting when his three children demonstrated it in their everyday behavior. Under these conditions, a great deal must be known about the infant’s daily life to be sure that deferred imitation—which requires infants to represent a model’s past behavior—has occurred.

Laboratory research, in contrast, suggests that deferred imitation is present at 6 weeks of age! Infants who watched an unfamiliar adult’s facial expression imitated it when exposed to the same adult the next day (Meltzoff & Moore, 1994). As motor capacities improve, infants copy actions with objects. In one study, an adult showed 6- and 9-month-olds a novel series of actions with a puppet: taking its glove off, shaking the glove to ring a bell inside, and replacing the glove. When tested a day later, infants who had seen the novel actions were far more likely to imitate them (see Figure 6.2). And when the adult paired a second, motionless puppet with the first puppet 1 to 6 days before the demonstration, 6- to 9-month-olds generalized the actions to this new, very different-looking puppet (Barr, Marrott, & Rovee-Collier, 2003; Giles & Rovee-Collier, 2011). Even more impressive, after having seen Puppet A paired with B and Puppet B paired with C on successive days, infants transferred modeled actions from A to C and from C to A, although they had not directly observed this pair together (Townsend & Rovee-Collier, 2007). Already, infants can form flexible mental representations that include chains of relevant associations.

Figure 6.2 Testing infants for deferred imitation. After researchers performed a novel series of actions with a puppet, this 6-month-old imitated the actions a day later: (a) removing the glove; (b) shaking the glove to ring a bell inside. With age, gains in recall are evident in deferred imitation of others’ behaviors over longer delays.

Courtesy of Carolyn Rovee-Collier

Gains in recall, expressed through deferred imitation, are accompanied by changes in brain-wave activity during memory tasks, as measured by event-related potentials (ERPs). This suggests that improvements in memory storage in the cerebral cortex contribute to these advances (Bauer et al., 2006). Between 12 and 18 months, toddlers use deferred imitation skillfully to enrich their range of schemes. They retain modeled behaviors for at least several months, copy the actions of peers as well as adults, and imitate across a change in context—for example, enact at home a behavior seen at child care (Meltzoff & Williamson, 2010; Patel, Gaylord, & Fagen, 2013). The ability to recall modeled behaviors in the order they occurred—evident as early as 6 months—also strengthens over the second year (Bauer, Larkina, & Deocampo, 2011; Rovee-Collier & Cuevas, 2009). And when toddlers imitate in correct sequence, they remember more behaviors.

Older infants and toddlers even imitate rationally, by inferring others’ intentions! They are more likely to imitate purposeful than accidental or arbitrary behaviors on objects. And they adapt their imitative acts to a model’s goals (Kolling, Óturai, & Knopf, 2014; Zmyj & Buttelmann, 2014). If 12-month-olds see an adult perform an unusual action for fun (make a toy dog enter a miniature house by jumping through the chimney, even though its door is wide open), they copy the behavior. But if the adult engages in the odd behavior because she must (she makes the dog go through the chimney only after first trying to use the door and finding it locked), 12-month-olds typically imitate the more efficient action (putting the dog through the door) (Schwier et al., 2006).

Between 14 and 18 months, toddlers become increasingly adept at imitating actions an adult tries to produce, even if these are not fully realized (Bellagamba, Camaioni, & Colonnesi, 2006; Olineck & Poulin-Dubois, 2009). On one occasion, Ginette attempted to pour some raisins into a small bag but missed, spilling them onto the counter. A moment later, Grace began dropping the raisins into the bag, indicating that she had inferred Ginette’s goal.

Though advanced in terms of Piaget’s predictions, toddlers’ ability to represent others’ intentions—a cornerstone of social understanding and communication—has roots in earlier sensorimotor activity (Rosander & von Hofsten, 2011). Infants’ skill at engaging in goal-directed actions—reaching for objects at 3 to 4 months, pointing to objects at 9 months—predicts their awareness of an adult’s similar behavior as goal-directed (Gerson & Woodward, 2010; Woodward, 2009). And the better 10-month-olds are at detecting the goals of others’ gazes and reaches, the more successful they are four months later at inferring an adult’s intention from her incomplete actions in an imitation task (Olineck & Poulin-Dubois, 2009).

Problem Solving

As Piaget indicated, around 7 to 8 months, infants develop intentional means–end action sequences that they use to solve sensorimotor problems, such as pulling on a cloth to obtain an out-of-reach toy resting on it or grasping a handle to secure a toy attached to its far end (Fagard et al., 2015; Willatts, 1999). Out of these explorations of object-to-object relations, the capacity for tool use in problem solving—manipulating an object (tool) as a means to a goal—emerges (Keen, 2011).

For example, 12-month-olds who were repeatedly presented with a spoon containing food, oriented so its handle pointed toward their preferred hand (usually the right), adapted their grip when the spoon’s handle was presented in the opposite orientation (to the left). As a result, they succeeded in transporting the food to their mouths most of the time (McCarty & Keen, 2005). With age, babies increasingly adjusted their grip to fit the spoon’s orientation in advance, planning ahead for what they wanted to do with the tool.

In each of the tasks just mentioned, the tool and the object were physically linked. Not until the middle of the second year can toddlers engage in tool use when an unfamiliar tool and an object they want are spatially separated. In several studies, an adult presented 14- to 22-month-olds with an out-of-reach toy and a small rake that was placed to the side of the toy. Around 18 months, toddlers spontaneously began using the rake to get the toy, with the number doing so rising gradually with age (Fagard, Rat-Fischer, & O’Regan, 2014; Rat-Fischer, O’Regan, & Fagard, 2012). A demonstration of how to use the tool, in which the adult first highlighted her goal by stretching her arm and hand toward the toy and saying, “I can’t get it,” led 16-month-olds to try harder to rake in the toy, though they often did not succeed (Esseily et al., 2013; Fagard et al., 2016). Merely showing toddlers how to use the rake had little impact until 18 months, the age at which they began discovering the tool’s use on their own.

These findings suggest that around the middle of the second year, infants begin forming mental representations of how to use an unfamiliar tool to secure a desired object. As Piaget suggested, they have some ability to move beyond trial-and-error experimentation and represent a solution to a problem mentally.

Symbolic Understanding

One of the most momentous early attainments is the realization that words can be used to cue mental images of things not physically present—a symbolic capacity called displaced reference that emerges around the first birthday. It greatly enhances toddlers’ capacity to learn about the world through communicating with others. As we saw in our discussion of objects hidden in more than one location, 12-month-olds respond to the verbal label of an absent toy by looking at and gesturing toward a nearby spot where they last saw it. And on hearing the name of a parent or sibling who has just left the room, most 13-month-olds turn toward the door (DeLoache & Ganea, 2009). The more experience toddlers have with an object and its verbal label, the more likely they are to call up a mental representation when they hear the object’s name. As memory and vocabulary improve, skill at displaced reference expands.

But at first, toddlers have difficulty using language to acquire new information about an absent object—an ability that is essential for learning from symbols. In one study, an adult taught 19- and 22-month-olds a name for a stuffed animal—”Lucy”—a frog. Then, with the frog out of sight, each toddler was told that some water had spilled, so “Lucy’s all wet!” Finally, the adult showed the toddler three stuffed animals—a wet frog, a dry frog, and a pig—and said, “Get Lucy!” (Ganea et al., 2007). Although all the children remembered that Lucy was a frog, only the 22-month-olds identified the wet frog as Lucy. This capacity to use language as a flexible symbolic tool—to modify an existing mental representation—improves into the preschool years.

A beginning awareness of the symbolic function of pictures emerges in the first year, strengthening in the second. By 9 months, the majority of infants touch, rub, or pat a color photo of an object but rarely try to grasp it (Ziemer, Plumert, & Pick, 2012). These behaviors suggest that 9-month-olds do not mistake a picture for the real thing, though they may not yet comprehend it as a symbol. By the middle of the second year, toddlers clearly treat pictures symbolically, as long as the pictures strongly resemble real objects. After hearing a novel label (“blicket”) applied to a color photo of an unfamiliar object, most 15- to 24-month-olds—when presented with both the real object and its picture and asked to indicate the “blicket”—gave a symbolic response (Ganea et al., 2009). They selected either the real object or both the object and its picture, not the picture alone.

Around this time, toddlers frequently use pictures as vehicles for communicating with others and acquiring new knowledge. They point to, name, and talk about pictures, and they can apply something learned from a book with realistic-looking pictures to real objects, and vice versa (Ganea, Ma, & DeLoache, 2011; Simcock, Garrity, & Barr, 2011).

Picture-rich environments in which caregivers often direct babies’ attention to the link between pictures and their referents promote pictorial understanding. In non-Western cultures where pictures are rare, symbolic understanding of pictures is delayed (Callaghan et al., 2011). In a study carried out in a village community in Tanzania, Africa, where children receive no exposure to pictures before they start school, an adult taught 1½- to 3-year-olds a new name for an unfamiliar object during picture-book interaction (Walker, Walker, & Ganea, 2013). When later asked to pick the named object from arrays of pictures and real objects, not until 3 years of age did the Tanzanian children perform as well as U.S. 15-month-olds.

A 17-month-old points to a picture in a book, revealing her beginning awareness of the symbolic function of pictures. But pictures must be highly realistic for toddlers to treat them symbolically.

Social Issues: EducationBaby Learning from Screen Media: The Video Deficit Effect

Children first become TV and video viewers in early infancy, as they are exposed to programs watched by parents and older siblings or to ones specially aimed at baby viewers. U.S. parents report that 50 percent of 2-month-olds watch TV and videos, a figure that rises to 90 percent by 2 years of age. Smart phone and tablet use by children under age 2, who often view videos on these devices, is similar. Average screen time increases from 55 minutes per day at 6 months to just under 1½ hours per day at age 2 (Anand et al., 2014; Cespedes et al., 2014; Kabali et al., 2015). Although parents assume that babies learn from videos, research indicates that babies cannot take full advantage of them.

Initially, infants respond to videos of people as if viewing people directly—smiling, moving their arms and legs, and (by 6 months) imitating the actions of a televised adult (Barr, Muentener, & Garcia, 2007). But when shown videos of attractive toys, 9-month-olds touch and grab at the screen, suggesting that they confuse the images with the real thing. By the middle of the second year, manual exploration declines in favor of pointing at the images (Pierroutsakos & Troseth, 2003). Nevertheless, toddlers have difficulty applying what they see on video to real situations.

In a series of studies, some 2-year-olds watched through a window while an adult hid an object in an adjoining room, while others watched the same event on a video screen. Children in the direct-viewing condition retrieved the toy easily; those in the video condition had difficulty (Troseth, 2003). This video deficit effect—poorer performance after a video than a live demonstration—has also been found for 2-year-olds’ deferred imitation, word learning, and means–end problem solving (Bellagamba et al., 2012; Hayne, Herbert, & Simcock, 2003; Roseberry et al., 2009).

Making sense of complex video, even when it depicts familiar events, is cognitively challenging for toddlers, who require more time to process two-dimensional images than their three-dimensional real-life equivalents (Kirkorian, 2018; Kirkorian & Choi, 2017). In addition, video typically lacks social cues that support toddlers’ everyday learning, such as caregivers looking at and conversing with them directly and establishing a shared focus on objects.

In one study, researchers provided 12- to 25-month olds with a series of tablet sessions involving either real-time video chat through FaceTime or noninteractive, prerecorded videos. The two types of sessions were similar in content: An adult introduced herself, labeled novel toys, and read a book with a give-and-take verbal pattern. After a week of six 8- to 12-minute tablet sessions, only participants in the FaceTime condition recognized and preferred to play with their video partner in real life. The FaceTime condition also resulted in greater learning from book reading and, among the oldest toddlers, mastery of more novel words (Myers et al., 2017). In another investigation comparing an interactive video experience on closed circuit TV with a noninteractive video, 2-year-olds in the interactive condition were far more successful in using a verbal cue from an adult on video to retrieve a hidden toy in real life (Troseth, Saylor, & Archer, 2006).

Around age 2½, the video deficit effect declines. The American Academy of Pediatrics (American Academy of Pediatrics, 2016a) recommends against screen media exposure before 1½ to 2 years of age and, between 2 and 5 years, limiting it to one hour per day with parental coviewing. In support of this advice, amount of TV viewing is negatively related to toddlers’ language progress (Zimmerman, Christakis, & Meltzoff, 2007). And 1- to 3-year-old heavy viewers tend to have attention, memory, and reading difficulties in the early school years (Christakis et al., 2004; Zimmerman & Christakis, 2005).

An 18-month-old reaches toward a sad character in a children’s cartoon. Perhaps he has difficulty making sense of the image because the character does not look like his real-life social partners or converse with him directly, as adults do.

When toddlers do watch TV or video, it is likely to work best as a teaching tool when it is rich in social cues (Lauricella, Gola, & Calvert, 2011). These include use of familiar characters and close-ups in which the character looks directly at the camera, addresses questions to viewers, and pauses to invite a response. Interactive touchscreens may also help toddlers transfer information on the screen to real life, but only if their interactive elements direct toddlers’ attention to relevant features of word-learning and object-retrieval tasks (Kirkorian, Choi, & Pempek, 2016; Choi & Kirkorian, 2016).

Finally, video chat offers an exception to the video deficit effect. Toddlers readily learn from its socially contingent format, which helps them make connections between video and reality. Parents report often using video chat formats, such as Skype and FaceTime, to connect with their young children while separated from them and to promote relationships with distant relatives (McClure et al., 2015). Media experts recommend that video chat be exempt from restrictive screen media rules for infants and toddlers.

But even after coming to appreciate the symbolic nature of pictures, young children continue to have difficulty grasping the distinction between some pictures (such as line drawings) and their referents, as we will see in Chapter 8. How do infants and toddlers interpret another ever-present, pictorial medium—video? See the Social Issues: Education box above to find out.

6.1.4 Evaluation of the Sensorimotor Stage

Table 6.2 summarizes the remarkable cognitive attainments we have just considered. Compare this table with Piaget’s description of the sensorimotor substages in Table 6.1 on page 199. You will see that infants anticipate events, actively search for hidden objects, master the A–B object search, flexibly vary their sensorimotor schemes, mentally represent solutions to problems, engage in make-believe play, and treat pictures and video images symbolically within Piaget’s time frame. Yet other capacities—including secondary circular reactions, understanding of object properties, first signs of object permanence, deferred imitation, and displaced reference of words—emerge earlier than Piaget expected. These findings show that the cognitive attainments of infancy and toddlerhood do not develop together in the neat, stepwise fashion that Piaget predicted.

Recent research raises questions about Piaget’s view of how infant development takes place. Consistent with Piaget’s ideas, sensorimotor action helps infants construct some forms of knowledge. For example, as we saw in Chapter 5, crawling enhances depth perception and ability to find hidden objects, and handling objects fosters awareness of object properties. Yet we have also seen that infants comprehend a great deal before they are capable of the motor behaviors that Piaget assumed led to those understandings. How can we account for babies’ amazing cognitive accomplishments?

Alternative Explanations

Unlike Piaget, who thought babies constructed all mental representations out of sensorimotor activity, most researchers now believe that infants have some built-in cognitive equipment for making sense of experience. But intense disagreement exists over the extent of this initial understanding. As we have seen, much evidence on young infants’ cognition rests on the violation-of-expectation method. Researchers who lack confidence in this method argue that babies’ cognitive starting point is limited (Bremner, Slater, & Johnson, 2015; Cohen, 2010; Kagan, 2013c). For example, some believe that newborns begin life with a set of biases for attending to certain information and with general-purpose learning procedures—such as powerful techniques for analyzing complex perceptual information (Bahrick, 2010; MacWhinney, 2015; Rakison, 2010). Together, these capacities enable infants to construct a wide variety of schemes.

Others, convinced by violation-of-expectation findings, believe that infants start out with impressive understandings. According to this core knowledge perspective, babies are born with a set of innate knowledge systems, or core domains of thought. Each of these prewired understandings permits a ready grasp of new, related information and therefore supports early, rapid development (Carey, 2009; Leslie, 2004; Spelke, 2016; Spelke & Kinzler, 2013). Core knowledge theorists argue that infants could not make sense of the complex stimulation around them without having been genetically “set up” in the course of evolution to comprehend its crucial aspects.

Table 6.2 Some Cognitive Attainments of Infancy and Toddlerhood

Age

Cognitive Attainments

Birth–1 month

Secondary circular reactions using limited motor skills, such as sucking a nipple to gain access to interesting sights and sounds

1–4 months

Awareness of object permanence, object solidity, and gravity, as suggested by violation-of-expectation findings; deferred imitation of an adult’s facial expression over a short delay (one day)

4–8 months

Improved knowledge of object properties and basic numerical knowledge, as suggested by violation-of-expectation findings; deferred imitation of an adult’s novel actions on objects over a short delay (one to three days)

8–12 months

Improved anticipation of events (such as parent’s departure) and efforts to change those events; ability to search for a hidden object when covered by a cloth

12–18 months

Ability to search for a hidden object when it is moved from one location to another (accurate A–B search); deferred imitation of an adult’s novel actions on objects after long delays (at least several months) and across a change in context (from child care to home); rational imitation, inferring the model’s intentions; displaced reference of words

18 months–2 years

Ability to find an object moved while out of sight (invisible displacement); deferred imitation of actions an adult tries to produce, even if these are not fully realized; beginnings of make-believe play; ability to mentally represent the solution to a problem, in using an unfamiliar tool to secure an object; increasing awareness of pictures and video as symbols of reality

Researchers have conducted many studies of infants’ physical knowledge, including object permanence, object solidity (that one object cannot move through another), and gravity (that an object will fall without support). Violation-of-expectation findings suggest that in the first few months, infants have some awareness of all these basic object properties and quickly build on this knowledge (Baillargeon et al., 2011). Core knowledge theorists also assume that an inherited foundation of linguistic knowledge enables swift language acquisition in early childhood—a possibility we will consider later in this chapter. Furthermore, these theorists argue, infants’ early orientation toward people initiates rapid development of psychological knowledge—in particular, understanding of mental states, such as intentions, emotions, desires, and beliefs, which we will address further in Chapter 7.

Research even suggests that infants have basic numerical knowledge. In the best-known study, 5-month-olds saw a screen raised to hide a single toy animal and then watched a hand place a second toy behind the screen. Finally, the screen was removed to reveal either one or two toys. If infants kept track of the two objects (requiring them to add one object to another), then they should look longer at the unexpected, one-toy display—which is what they did (see Figure 6.3) (Wynn, 1992). These findings and others suggest that babies can discriminate quantities up to three and use that knowledge to perform simple arithmetic—both addition and subtraction (in which two objects are covered and one object is removed) (Kobayashi, Hiraki, & Hasegawa, 2005; Walden et al., 2007; Wynn, Bloom, & Chiang, 2002). As further support, ERP brain-wave recordings taken while infants view correct and incorrect simple arithmetic solutions reveal a response pattern identical to the pattern adults show when detecting errors (Berger, Tzur, & Posner, 2006).

Did this toddler learn to build a tower of cans by repeatedly acting on objects, as Piaget assumed? Or did he begin life with innate knowledge that helps him understand objects and their relationships quickly, with little hands-on exploration?

Figure 6.3 Testing infants for basic number concepts. (a) First, infants saw a screen raised in front of a toy animal. Then an identical toy was added behind the screen. Next, the researchers presented two outcomes. (b) In the expected outcome, the screen dropped to reveal two toy animals. (c) In the unexpected outcome, the screen dropped to reveal one toy animal. Five-month-olds shown the unexpected outcome looked longer than did 5-month-olds shown the expected outcome. The researchers concluded that infants can discriminate the quantities “one” and “two” and use that knowledge to perform simple addition: 1+1=2. A variation of this procedure suggested that 5-month-olds could also do simple subtraction: 2−1=1. (From K. Wynn, 1992, “Addition and Subtraction by Human Infants,” Nature, 358, p. 749. © 1992, Nature Publishing Group. Adapted with permission of Nature Publishing Group in the format “Republish in a book” via Copyright Clearance Center.)

Additional evidence suggests that 6-month-olds can distinguish among large sets of items, as long as the difference between those sets is very great—at least a factor of two. For example, they can tell the difference between 8 and 16 dots but not between 8 and 12 (Lipton & Spelke, 2003; Xu, Spelke, & Goddard, 2005). Furthermore, 6-month-olds’ factor-of-two discrimination capacity is similar across quantitative dimensions. It also applies to the area of spatial surfaces and the duration of tones (Brannon, Lutz, & Cordes, 2006; Lipton & Spelke, 2003; VanMarle & Wynn, 2006). Consequently, some researchers believe that in addition to making small-number discriminations, infants can represent approximate large-number values and that their ability to do so reflects a more general quantitative understanding.

But as with other violation-of-expectation results, this evidence is controversial. Skeptics question whether other aspects of object displays, rather than numerical sensitivity, are responsible for the findings (Bremner, Slater, & Johnson, 2015; Clearfield & Westfahl, 2006). Indisputable evidence for built-in core knowledge requires that it be demonstrated at birth or close to it—in the absence of relevant opportunities to learn. Yet findings on newborns’ ability to process small and large numerical values are inconsistent (Coubart et al., 2014; Izard et al., 2009). And critics point out that claims for infants’ number knowledge are surprising, in view of other research indicating that before 14 to 16 months, toddlers have difficulty making less-than and greater-than comparisons between small sets. As we will see in Chapter 9, not until the preschool years do children add and subtract small sets correctly.

The core knowledge perspective, while emphasizing native endowment, acknowledges that experience is essential for children to extend this initial knowledge. But so far, it has said little about which experiences are most important in each core domain and how those experiences advance children’s thinking. Despite these limitations, core knowledge investigators have sharpened the field’s focus on clarifying the starting point for human cognition and on carefully tracking the changes that build on it.

Piaget’s Legacy

Current research on infant cognition yields broad agreement on two issues. First, many cognitive changes of infancy are not abrupt and stagelike but gradual and continuous (Bjorklund & Causey, 2018). Second, rather than developing together, various aspects of infant cognition change unevenly because of the challenges posed by different types of tasks and infants’ varying experiences with them. These ideas serve as the basis for another major approach to cognitive development—information processing—which we take up next.

Before we turn to this alternative point of view, let’s recognize Piaget’s enormous contributions. Piaget’s work inspired a wealth of research on infant cognition, including studies that challenged his theory. Today, researchers are far from consensus on how to modify or replace his account of infant cognitive development, and some believe that his general approach continues to make sense and fits most of the evidence (Cohen, 2010; Lourenço, 2016). Piaget’s observations also have been of great practical value. Teachers and caregivers continue to look to the sensorimotor stage for guidelines on how to create developmentally appropriate environments for infants and toddlers.

Now that you are familiar with some milestones of the first two years, what play materials do you think would support the development of sensorimotor and early representational schemes? Prepare a list, justifying it by referring to the cognitive attainments described in the previous sections. Then compare your suggestions to the ones given in Applying What We Know on page 210.

Ask Yourself

Connect ■ Which of the capacities listed in Table 6.2 indicate that mental representation emerges earlier than Piaget concluded?

Apply ■ Several times, after her father hid a teething biscuit under a red cup, 12-month-old Mimi retrieved it easily. Then Mimi’s father hid the biscuit under a nearby yellow cup. Why did Mimi persist in searching for it under the red cup?

Reflect ■ What advice would you give the typical U.S. parent about permitting an infant or toddler to watch as much as 1 to 1½ hours of TV or video per day? Explain.

Applying What We Know

Play Materials That Support Infant and Toddler Cognitive Development

From 2 Months

From 6 Months

From 1 Year

Crib mobile

Rattles and other handheld sound-making toys, such as a bell on a handle

Adult-operated music boxes and music recordings with gentle, regular rhythms, songs, and lullabies

Squeeze toys

Nesting cups

Clutch and texture balls

Stuffed animals and soft-bodied dolls

Filling and emptying toys

Large and small blocks

Pots, pans, and spoons from the kitchen

Simple, floating objects for the bath

Picture books with realistic color images

Large dolls, toy dishes, toy telephone

Cars and trucks

Large blocks, cardboard boxes

Hammer-and-peg toy

Pull and push toys, riding toys that can be pushed with feet

Rhythm instruments for shaking and banging, such as bells, cymbals, and drums

Simple puzzles

Sandbox, shovel, and pail

Shallow wading pool and water toys

Balls of various sizes

6.2 INFORMATION PROCESSING

6.2a Describe the information-processing view of cognitive development and the general structure of the information-processing system.

6.2b Describe changes in attention, memory, and categorization over the first two years.

6.2c Explain the strengths and limitations of the information-processing approach to early cognitive development.

Advocates of the information-processing approach agree with Piaget that children are active, inquiring beings. However, instead of proposing a single, unified theory of cognitive development, they focus on many aspects of thinking, from attention, memory, and categorization skills to complex problem solving. Furthermore, information-processing researchers are not satisfied with general concepts, such as assimilation and accommodation, to explain how children think. Rather, they want to know exactly what individuals of different ages do when faced with a task or problem (Birney & Sternberg, 2011). As we saw in Chapter 1, the information-processing perspective often relies on computerlike flowcharts to model the human cognitive system. This way of representing thinking is attractive because it is explicit and precise.

6.2.1 Assumptions of the Information-Processing Perspective

Information-processing researchers generally assume that we hold information in three parts of the cognitive system for processing: the sensory store, the short-term memory store, and the long-term memory store (see Figure 6.4). Initially, most viewed processing as occurring in a serial, step-by-step fashion, with information moving through the stores in the order just mentioned. Today, investigators realize that information is often held and processed in the three stores simultaneously (Bjorklund & Causey, 2016). For example, when putting together a complex jigsaw puzzle, you might continuously refer to a visual image held in long-term memory as a “big picture” guide to which puzzle pieces to focus on in the sensory store and how to manipulate the selected pieces in the short-term memory store.

As information flows between the stores, we use mental strategies to operate on and transform it, increasing the chances that we will retain the information; use it efficiently and flexibly, adapting it to changing circumstances; and pass it to the next store, eventually producing an effective response. To understand this more clearly, let’s look at each aspect of the cognitive system.

Figure 6.4 The information-processing system. Information is held and often simultaneously processed in three parts of the cognitive system: the sensory store, the short-term memory store, and the long-term memory store. In each, mental strategies can be used to manipulate information, increasing the efficiency and flexibility of thinking and the chances that information will be retained. The central executive is the conscious, reflective part of working memory. It coordinates incoming information already in the system, decides what to attend to, and oversees the use of strategies.

In the sensory store, sights and sounds in the surrounding world are represented directly and stored momentarily. Look around you, and then close your eyes. An image of what you saw persists for a few seconds, but then it decays, or disappears, unless you use mental strategies to preserve it. For example, by attending to some information more carefully than to other information, you increase the chances that it will transfer to the other stores.

As information enters the short-term memory store, we retain it briefly so we can actively “work” on it to reach our goals. One way of looking at the short-term store is in terms of its basic capacity, often referred to as short-term memory: the number of pieces of information a person can hold in mind at once for a few seconds. But most researchers endorse a contemporary view of the short-term store, which is a more meaningful indicator of its capacity, called working memory—the number of items a person can briefly hold in mind while also engaging in some effort to monitor or manipulate those items. Working memory can be thought of as a “mental workspace” that we use to accomplish many activities in daily life. From childhood on, researchers assess changes in its capacity by presenting individuals with lists of items (such as numerical digits or short sentences), asking them to “work on” the items (for example, repeat the digits backward or remember the final word of each sentence in correct order), and seeing how well they do.

The sensory store can take in a wide panorama of information. Short-term and working memory are far more restricted, though their capacity increases steadily from early childhood through adolescence—from about two to seven items on a verbatim numerical digit-span task to about two to five items on working-memory tasks (Cowan & Alloway, 2009). Still, individual differences are evident at all ages. By engaging in a variety of basic cognitive procedures, such as focusing attention on relevant items and repeating (rehearsing) them rapidly, we increase the chances that information will be retained and accessible to ongoing thinking.

The central executive manages the cognitive system’s activities, directing the flow of information, implementing the basic procedures just mentioned, and also engaging in more sophisticated activities that enable complex, flexible thinking. For example, the central executive coordinates incoming information with information already in the system, and it selects, applies, and monitors strategies that facilitate memory storage, comprehension, reasoning, and problem solving. The central executive is the conscious, reflective part of our cognitive system. It ensures that we think purposefully to attain our goals.

The more effectively the central executive joins with working memory to process information, the better learned cognitive activities will be and the more automatically we can apply them. Consider the richness of your thinking while you automatically drive a car. Automatic processes are so well-learned that they require no space in working memory and, therefore, permit us to focus on other information while performing them.

Effective processing of information in working memory increases the likelihood that it will transfer to the third, and largest, storage area—the long-term memory store, our permanent knowledge base, which has a massive capacity. In fact, we store so much in long-term memory that retrieval—getting information back from the system—can be problematic. To aid retrieval, we apply strategies, just as we do in memory storage. Information in long-term memory is categorized by its contents, much like a digital library reference system that enables us to retrieve items by following the same network of associations used to store them in the first place.

Information-processing researchers believe that several aspects of the cognitive system improve during childhood and adolescence: (1) the basic capacity of its stores, especially working memory; (2) the speed with which information is worked on; and (3) the functioning of the central executive. Together, these changes make possible more complex forms of thinking with age (Halford & Andrews, 2011).

Gains in working-memory capacity are due in part to brain development, but greater processing speed also contributes. Fast, fluent thinking frees working-memory resources to support storage and manipulation of additional information. Furthermore, researchers have become intensely interested in studying the development of executive function—the diverse cognitive operations and strategies that enable us to achieve our goals in cognitively challenging situations (Zelazo & Carlson, 2012). These include controlling attention by inhibiting impulses and irrelevant actions and by flexibly directing thought and behavior to suit the demands of a task; coordinating information in working memory; and planning—capacities governed by the prefrontal cortex and its elaborate connections to other brain regions (Chevalier, 2015). Measures of executive function predict important cognitive and social outcomes in childhood, adolescence, and adulthood, such as task persistence, self-control, academic achievement, and interpersonal acceptance (Carlson, Zelazo, & Faja, 2013; Müller & Kerns, 2015).

Gains in aspects of executive function are under way in the first two years. Dramatic strides will follow in childhood and adolescence.

6.2.2 Attention

Newborns show a primitive ability to control attention, evident in their preference for looking at simplified but coherent stimuli—for example, upright rather than inverted faces (see page 189 in Chapter 5) (Daum, 2016). Recall, also, that around 2 to 3 months of age, infants shift from focusing on single, high-contrast features to exploring objects and patterns more thoroughly (Frank, Amso, & Johnson, 2014). When presented with a complex scene, such as a Charlie Brown cartoon video, infants transitioned between 3 and 9 months from scattered attention to areas of changing color, brightness, and motion throughout the screen to more narrowly focused attention to characters’ faces (Frank, Vul, & Johnson, 2009). With age, infants seemed better able to inhibit attending to distracting background stimuli and to focus on socially meaningful information.

Besides improving in attentional control, infants gradually become more efficient at managing their attention, taking in information more quickly. Habituation research reveals that preterm and newborn babies require a long time—about three to four minutes—to habituate and recover to novel visual stimuli. But by 4 or 5 months, they need as little as 5 to 10 seconds to take in a complex visual stimulus and recognize it as different from a previous one (Colombo, Kapa, & Curtindale, 2011).

At the end of the first year, as the prefrontal cortex improves in its executive role and babies become increasingly capable of intentional behavior (refer to Piaget’s Substage 4), attraction to novelty declines (but does not disappear) and sustained attention increases (Posner et al., 2012). This change is especially evident when children play with toys. A toddler who engages even in simple goal-directed behavior, such as stacking blocks or putting them in a container, must sustain attention to reach the goal. As plans and activities gradually become more complex, the duration of attention expands.

Adults can foster sustained attention by encouraging babies’ current interest (“Oh, you like that bell!”) and prompting the child to stay focused (“See, it makes a noise!”). Consistently helping infants focus attention at 10 months predicts higher intelligence test scores at 18 months (Bono & Stifter, 2003). Also, from age 3 months on, infants looking at faces are especially attracted to human eyes, and gradually they become more interested in what others are attending to (Dupierrix et al., 2014). Later we will see that this joint attention between caregiver and child is important for language development.

By encouraging her toddler’s goal-directed play, this mother promotes sustained attention.

6.2.3 Memory

Methods devised to assess infants’ short-term memory, which require keeping in mind an increasingly longer sequence of very briefly presented visual stimuli, reveal that retention increases from one visual item at age 6 months to two to four visual items at 12 months (Oakes, Ross-Sheehy, & Luck, 2007; Kwon, Luck, & Oakes, 2014). Furthermore, using a clever technique requiring infants to momentarily retain two visual stimuli while also monitoring their unique locations, researchers reported that working memory emerges between 8 and 10 months of age (Kaldy, Guillory, & Blaser, 2016).

Operant conditioning and habituation techniques, which grant babies more time to process information, provide windows into early development of long-term memory. Both methods show that retention of visual events improves greatly with age.

Operant Conditioning Research

Using operant conditioning, researchers study infant memory by teaching 2- to 6-month-olds to move a mobile by kicking a foot tied to it with a long cord. Two-month-olds remember how to activate the mobile for one to two days after training, and 3-month-olds for one week. By 6 months, memory increases to two weeks (Rovee-Collier, 1999; Rovee-Collier & Bhatt, 1993). Around the middle of the first year, babies can manipulate switches or buttons to control stimulation. When 6- to 18-month-olds pressed a lever to make a toy train move around a track, duration of memory continued to increase with age; 13 weeks after training, 18-month-olds still remembered how to press the lever (Hartshorn et al., 1998b). Figure 6.5 on page 214 shows this dramatic rise in retention of operant responses over the first year and a half.

Memory for operant responses improves dramatically over the first 18 months. This 12-month-old has learned to press a lever to make a toy train move around a track—an operant response she is likely to remember when re-exposed to the task many weeks later.

COURTESY OF CAROLYN ROVEE-COLLIER

Even after 2- to 6-month-olds forget an operant response, they need only a brief prompt—an adult who shakes the mobile—to reinstate the memory (Hildreth & Rovee-Collier, 2002; Fagen, Ohr, & Boller, 2016). And when 6-month-olds are given a chance to reactivate the response themselves for just a couple of minutes—jiggling the mobile by kicking or moving the train by lever-pressing—their memory not only returns but also extends dramatically to about 17 weeks (Rovee-Collier & Cuevas, 2009). Perhaps permitting the baby to generate the previously learned behavior strengthens memory because it re-exposes the child to more aspects of the original learning situation. Furthermore, with just five widely spaced adult-provided reminders of the train task extending over 1½ years, infants trained at age 6 months still remembered the response after reaching their second birthday (Hartshorn, 2003).

At first, infants’ memory for operant responses is highly context-dependent. If on the day after training 2- to 6-month-olds are not tested in the same situation in which training took place—with the same mobile and crib bumper and in the same room—they remember poorly (Hayne, 2004). After 9 months, the importance of context declines. Older infants and toddlers remember how to make the toy train move even when its features are altered and testing takes place in a different room (Hartshorn et al., 1998a; Learmonth, Lamberth, & Rovee-Collier, 2004). Crawling is strongly associated with 9-month-olds’ formation of an increasingly context-free memory (Herbert, Gross, & Hayne, 2007). As infants move on their own and experience frequent changes in context, they apply learned responses more flexibly, generalizing them to relevant new situations.

Figure 6.5 Increase in retention in two operant conditioning tasks from 2 to 18 months. Two- to 6-month-olds were trained to make a kicking response that turned a mobile. Six- to 18-month-olds were trained to press a lever that made a toy train move around a track. Six-month-olds learned both responses and retained them for an identical length of time, indicating that the tasks are comparable. Consequently, researchers could plot a single line of gains in retention from 2 to 18 months of age. The line shows that memory improves dramatically. (From C. Rovee-Collier & R. Barr, 2001, “Infant Learning and Memory,” in G. Bremner & A. Fogel [Eds.], Blackwell Handbook of Infant Development, Oxford, U.K.: Blackwell, p. 150. © 2001, 2004 by Blackwell Publishing Ltd.)

Habituation Research

Habituation studies show that infants learn and retain a wide variety of information just by watching objects and events, without being physically active. Sometimes they do so for much longer time spans than in operant conditioning studies. Babies are especially attentive to the movements of objects and people. For example, 3-month-olds’ retention of the unusual movements of objects (such as a metal nut swinging on the end of a string) persists for at least three months (Bahrick, Hernandex-Reif, & Pickens, 1997). By contrast, infants’ memory for the faces of unfamiliar people and the features of objects is short-lived—24 hours at 3- to 5-months, extending to just several days to a few weeks at the end of the first year (Fagan, 1973; Pascalis, de Haan, & Nelson, 1998).

By 10 months, infants remember both novel actions and features of objects involved in those actions equally well (Baumgartner & Oakes, 2011). Thus, over the second half-year, sensitivity to object appearance increases. This change, as noted earlier, is fostered by infants’ increasing ability to manipulate objects, which helps them learn about objects’ observable properties.

Habituation research confirms that infants need not be physically active to acquire new information. Nevertheless, as illustrated by research presented in Chapter 5 on the facilitating role of crawling in infants’ ability to find hidden objects (see page 188), motor activity does promote certain aspects of learning and memory.

Recall Memory

So far, we have discussed only recognition—noticing when a stimulus is identical or similar to one previously experienced. It is the simplest form of memory: All babies have to do is indicate (by kicking, pressing a lever, or looking) whether a new experience is identical or similar to a previous one. Recall is more challenging because it involves remembering something not present. To recall, you must generate a mental image of the past experience. Can infants engage in recall? By the middle of the first year, they can, as indicated by their ability to find hidden objects and engage in deferred imitation.

Recall memory improves steadily with age, with older infants recalling more information over longer time periods. For example, 1-year-olds can retain short sequences of adult-modeled behaviors they have observed several times for up to three months, and 1½–year-olds can do so for as long as 12 months. The ability to recall a sequence of modeled behaviors in the order in which the actions occurred—evident at 9 months—strengthens over the second year (Bauer, 2013; Bauer, Larkina, & Deocampo, 2011; Lukowski, Wiebe, & Bauer, 2009). And when toddlers imitate in correct sequence, processing not just separate actions but relations between actions, they remember more (Knopf, Kraus, & Kressley-Mba, 2006).

Long-term recall depends on connections among multiple regions of the cerebral cortex, especially with the prefrontal cortex. Formation of these neural circuits is under way in infancy and toddlerhood and will accelerate in early childhood (Jabès & Nelson, 2014). The evidence as a whole indicates that infants’ memory processing is remarkably similar to that of older children and adults: Babies have distinct short-term and long-term memories and display both recognition and recall. And they acquire information quickly and retain it over time, doing so more effectively with age (Howe, 2015). Furthermore, recall assessed through deferred imitation tasks at age 20 months predicts performance on memory tests at age 6, suggesting continuity of memory functions over time (Riggins et al., 2013). Yet a puzzling finding is that older children and adults no longer recall their earliest experiences! See the Biology and Environment box on page 216 for a discussion of infantile amnesia.

6.2.4 Categorization

Even young infants can categorize, grouping similar objects and events into a single representation (Rakison & Lawson, 2013). Categorization reduces the enormous amount of new information infants encounter every day, helping them learn and remember.

Creative variations of operant conditioning research with mobiles have been used to investigate infant categorization. One such study of 3-month-olds is described and illustrated in Figure 6.6. Similar investigations reveal that in the first few months, babies categorize stimuli on the basis of shape, size, and other physical properties (Wasserman & Rovee-Collier, 2001). By 6 months of age, they can categorize on the basis of two correlated features—for example, the shape and color of an alphabet letter (Bhatt et al., 2004). This ability to categorize using clusters of features prepares babies for acquiring many complex everyday categories.

Infant categorization has also been studied using habituation. Researchers show babies a series of pictures belonging to one category and then see whether they recover to (look longer at) a picture that is not a member of the category (see Figure 6.8 on page 217). Findings reveal that in the second half of the first year, infants group familiar objects into an impressive array of categories—food items, furniture, birds, land animals, air animals, sea animals, plants, vehicles, kitchen utensils, and spatial location (“above” and “below,” “on” and “in”) (Bornstein, Arterberry, & Mash, 2010; Casasola & Park, 2013; Sloutsky, 2015). Besides organizing the physical world, infants of this age categorize their emotional and social worlds. They sort people and their voices by gender and age, have begun to distinguish emotional expressions, can separate people’s natural actions (walking) from other motions, and expect people (but not inanimate objects) to move spontaneously (Spelke, Phillips, & Woodward, 1995; see also page 188 in Chapter 5).

Babies’ earliest categories are based on similar overall appearance or prominent object part: legs for animals, wheels for vehicles. But as infants approach their first birthday, more categories appear to be based on subtle sets of features (Mandler, 2004; Quinn, 2008). Older infants can even make categorical distinctions when the perceptual contrast between two categories is minimal (birds versus airplanes).

As they gain experience in comparing to-be-categorized items in varied ways and their store of verbal labels expands, toddlers start to categorize flexibly: When 14-month-olds are given four balls and four blocks, some made of soft rubber and some of rigid plastic, their sequence of object touching reveals that after classifying by shape, they can switch to classifying by material (soft versus hard) if an adult calls their attention to the new basis for grouping (Ellis & Oakes, 2006).

Figure 6.6 Investigating infant categorization using operant conditioning. Three-month-olds were taught to kick to move a mobile that was made of small blocks, all with the letter A on them. After a delay, kicking returned to a high level only if the babies were shown a mobile whose blocks were labeled with the same form (the letter A). If the form was changed (from As to 2s), infants no longer kicked vigorously. While making the mobile move, the babies had grouped together its features. They associated the kicking response with the category A and, at later testing, distinguished it from the category 2. (Bhatt, Rovee-Collier, & Weiner, 1994; Hayne, Rovee-Collier, & Perris, 1987).

Courtesy of Carolyn Rovee-Collier

Biology and EnvironmentInfantile Amnesia

If infants and toddlers recall many aspects of their everyday lives, how do we explain infantile amnesia—that most of us can retrieve few, if any, events that happened to us before age 2½ to 3? The reason cannot be merely the passage of time because we can recall many personally meaningful one-time events from both the recent and the distant past: the day a sibling was born or a move to a new house—recollections known as autobiographical memory.

Several explanations of infantile amnesia have been proposed. One theory credits brain development, pointing to the hippocampus (located just under the temporal lobes of the cerebral cortex), which plays a vital role in the formation of new memories. Though its overall structure is formed prenatally, the hippocampus continues to add new neurons well after birth. Integrating those neurons into existing neural circuits is believed to disrupt already stored early memories (Josselyn & Frankland, 2012). In support of this view, the decline in production of hippocampal neurons—in monkeys and rats as well as in humans—coincides with the ability to form stable, long-term memories of unique experiences.

Another conjecture is that older children and adults often use verbal means for storing information, whereas infants’ and toddlers’ memory processing is largely nonverbal—an incompatibility that may prevent long-term retention of early experiences. To test this idea, researchers sent two adults to the homes of 2- to 4-year-olds with an unusual toy that the children were likely to remember: The Magic Shrinking Machine, shown in Figure 6.7. One adult showed the child how, after inserting an object in an opening on top of the machine and turning a crank that activated flashing lights and musical sounds, the child could retrieve a smaller, identical object (discreetly dropped down a chute by the second adult) from behind a door on the front of the machine.

A day later, the researchers tested the children to see how well they recalled the event. Their nonverbal memory—based on acting out the “shrinking” event and recognizing the “shrunken” objects in photos—was excellent. But even when they had the vocabulary, children younger than age 3 had trouble describing features of the “shrinking” experience. Verbal recall increased sharply between ages 3 and 4—the period during which children “scramble over the amnesia barrier” (Simcock & Hayne, 2003, p. 813). In a follow-up study, which assessed verbal recall 6 years later, only 19 percent—including two children who had been younger than age 3— remembered the “shrinking” event (Jack, Simcock, & Hayne, 2012). Those who recalled were more likely to have participated in conversations about the experience with a parent, which could have helped them gain verbal access to the memory.

These findings help us reconcile infants’ and toddlers’ remarkable memory skills with infantile amnesia. During the first few years, children rely heavily on nonverbal memory techniques, such as visual images and motor actions. As language emerges, their ability to use it to refer to preverbal memories requires considerable support from adults. After age 3, when children increasingly represent autobiographical events in verbal form, they use language-based cues to retrieve them, which strengthens the accessibility of memories at later ages (Peterson, Warren, & Short, 2011).

Other evidence indicates that the advent of a clear self-image contributes to the end of infantile amnesia. For example, among children and adolescents, the average age of earliest memory is around age 2 to 2½ (Howe, 2014; Tustin & Hayne, 2010). Though these recollections are sparse in information recalled, their timing coincides with the age at which toddlers display firmer self-awareness, reflected in pointing to themselves in photos and referring to themselves by name.

Very likely, both neurological change and social experience contribute to the decline of infantile amnesia. Brain development and adult–child interaction may jointly foster self-awareness, language, and improved memory, which enable children to talk with adults about significant past experiences (Howe, 2015). As a result, preschoolers begin to construct a long-lasting autobiographical narrative of their lives and enter into the history of their family and community.

Figure 6.7 The Magic Shrinking Machine, used to test young children’s verbal and nonverbal memory of an unusual event. After being shown how the machine worked, the child participated in selecting objects from a polka-dot bag, dropping them into the top of the machine (a), and turning a crank, which produced a “shrunken” object (b). When tested the next day, 2- to 4-year-olds’ nonverbal memory for the event was excellent. But below 36 months, verbal recall was poor, based on the number of features recalled about the game during an open-ended interview (c). Recall improved between 36 and 48 months, the period during which infantile amnesia subsides. (From G. Simcock & H. Hayne, 2003, “Age-Related Changes in Verbal and Nonverbal Memory During Early Childhood,” Developmental Psychology, 39(5), pp. 807, 809. Copyright © 2003 by the American Psychological Association. Photos: Ross Coombes/Courtesy of Harlene Hayne.

In addition to touching and sorting, toddlers’ categorization skills are evident in their imitative and play behaviors. After watching an adult give a toy dog a drink from a cup, most 9- to 14-month-olds shown a rabbit and a motorcycle offered the drink only to the rabbit. Similarly, after watching an adult start a toy car with a key, older infants and toddlers imitated the action with a truck but not a rabbit (Mandler & McDonough, 1996, 1998). They clearly understood that certain actions are appropriate for some categories of items (animals) but not for others (vehicles).

By the end of the second year, toddlers’ grasp of the animate–inanimate distinction expands. Nonlinear motions are typical of animates (a person or a dog jumping), and linear motions of inanimates (a car or a table pushed along a surface). At 18 months, toddlers more often imitate a nonlinear motion with a toy that has animatelike parts (legs), even if it represents an inanimate (a bed). At 22 months, displaying a fuller understanding, they imitate a nonlinear motion only with toys in the animate category (a cat but not a bed) (Rakison, 2005). They seem to realize that whereas animates are self-propelled and therefore have varied paths of movement, inanimates move only when acted on in highly restricted ways.

Figure 6.8 Using habituation to study infant categorization. After habituating to a series of items belonging to one category (in this example, animals), infants are shown two novel items, one that is a member of the category (dog) and one that is not (car). If infants recover to (look longer at or spend more time manipulating) the out-of-category item (car), this indicates that they distinguish it from the set of within-category items (animals). Habituating another group of infants to a series of vehicles and seeing if, when presented with the two test items above, they recover to the dog confirms that babies can distinguish animals from vehicles. This pattern of responding has been found in many infant categorization studies.

Researchers disagree on how babies arrive at these impressive attainments. One view holds that older infants and toddlers categorize more effectively because they become increasingly sensitive to fine-grained perceptual features and to stable relations among those features—for example, objects with flapping wings and feathers belong to one category; objects with rigid wings, windows, and a smooth surface belong to another category (Madole, Oakes, & Rakison, 2013; Schultz, 2011). An alternative view is that before the end of the first year, babies undergo a fundamental shift from a perceptual to a conceptual basis for constructing categories, increasingly grouping objects by their common function or behavior (birds versus airplanes, cars versus trucks, dogs versus cats) (Mandler, 2004; Träuble & Pauen, 2011).

Look and Listen

Observe a toddler playing with a variety of small toys—some representing animals and some representing household objects. What play behaviors reveal the child’s ability to categorize?

But all acknowledge that exploration of objects and expanding knowledge of the world contribute (Mash & Bornstein, 2012). In addition, adult labeling of a set of objects with a consistently applied word—”Look at the car!” “Do you see the car?”—calls babies’ attention to commonalities among objects, fostering categorization as early as 3 to 4 months of age (Althaus & Plunkett, 2016; Ferry, Hespos, & Waxman, 2010). Toddlers’ vocabulary growth, in turn, promotes categorization by highlighting new categorical distinctions (Cohen & Brunt, 2009).

By age 2, toddlers can use conceptual similarity to guide behavior in increasingly novel situations, which greatly enhances the flexibility of their problem solving. In one study, 24-month-olds watched as an adult constructed a toy animal resembling a monkey using wooden, Velcro, and plastic pieces and then labeled it a “thornby.” A day later, the toddlers were given a different set of wooden, Velcro, and plastic materials that, when put together, resembled a rabbit (Hayne & Gross, 2015). Those asked to make a “thornby” out of “these other things” readily formed a category and applied the adult’s actions with the first animal to constructing the second, novel animal. A control group not presented with verbal cues performed poorly.

6.2.5 Evaluation of Information-Processing Findings

The information-processing perspective underscores the continuity of human thinking from infancy into adult life. In attending to the environment, remembering everyday events, and categorizing objects, Caitlin, Grace, and Timmy think in ways that are remarkably similar to our own, though their cognitive processing is far from proficient. Findings on memory and categorization join with other research in challenging Piaget’s view of early cognitive development. Infants’ capacity to recall events and to categorize stimuli attests, once again, to their ability to mentally represent their experiences.

Information-processing research has contributed greatly to our view of infants and toddlers as sophisticated cognitive beings. But its central strength—analyzing cognition into its components, such as perception, attention, memory, and categorization—is also its greatest drawback: Information processing has had difficulty putting these components back together into a broad, comprehensive theory.

One approach to overcoming this weakness has been to combine Piaget’s theory with the information-processing approach, an effort we will explore in Chapter 12. A more recent trend has been the application of a dynamic systems view (see page 29 in Chapter 1) to early cognition. In this approach, researchers analyze each cognitive attainment to see how it results from a complex system of prior accomplishments and the child’s current goals (Spencer, Perone, & Buss, 2011; Schutte & DeGirolamo, 2017; Thelen & Smith, 2006). Once these ideas are fully tested, they may move the field closer to a more powerful view of how the minds of infants and children develop.

6.3 THE SOCIAL CONTEXT OF EARLY COGNITIVE DEVELOPMENT

6.3 Explain how Vygotsky’s concept of the zone of proximal development expands our understanding of early cognitive development.

Recall the description at the beginning of this chapter of Grace dropping shapes into a container. Notice that she learns about the toy with Ginette’s help. With adult support, Grace will become better at matching shapes to openings and dropping them into the container, gradually performing this and similar activities on her own. Throughout this chapter, we have seen other examples of how adult support fosters early cognitive attainments—using tools to access objects, understanding screen media, sustaining attention, retrieving autobiographical memories, and forming categories,

Lev Vygotsky’s sociocultural theory emphasizes that children live in rich social and cultural contexts that affect the way their cognitive world is structured (Bodrova & Leong, 2007; Lourenço, 2012). Vygotsky believed that complex mental activities, including voluntary attention, deliberate memory, categorization, and problem solving, have their origins in social interaction. Through joint activities with more mature members of their society, children master activities and think in ways that have meaning in their culture.

A special Vygotskian concept explains how this happens. The zone of proximal (or potential) development refers to a range of tasks that the child cannot yet handle alone but can do with the help of more skilled partners. To understand this idea, think about how a sensitive adult (such as Ginette) introduces a child to a new activity. The adult picks a task that the child can master but that is challenging enough that the child cannot do it by herself. Or the adult capitalizes on an activity that the child has chosen. The adult guides and supports, adjusting the level of support offered to fit the child’s current performance. As the child joins in the interaction and picks up mental strategies, her competence increases, and the adult steps back, permitting the child to take more responsibility for the task (Mermelshtine, 2017). This form of teaching—known as scaffolding—promotes learning at all ages, and we will consider it further in Chapter 9.

Vygotsky’s ideas have been applied mostly to preschool and school-age children, who are more skilled in language and social communication. Recently, however, his theory has been extended to infancy and toddlerhood. Picture an adult helping a baby figure out how a jack-in-the-box works. In the early months, the adult demonstrates and, as the clown pops out, tries to capture the infant’s attention by saying something like “See what happened!” By the end of the first year, when cognitive and motor skills have improved, interaction centers on how to use the toy: The adult guides the baby’s hand in turning the crank. During the second year, the adult helps from a distance using gestures and verbal prompts, such as making a turning motion and verbally prompting, “Turn it!” Research indicates that this fine-tuned support is related to advanced play, language, and problem solving during the second year—for example, transferring how a simple toy works on a touchscreen to the same toy in real life, which is highly challenging for toddlers (Bornstein et al., 1992; Charman et al., 2001; Zack & Barr, 2016).

As early as the first year, cultural variations in social experiences affect mental strategies. In the jack-in-the-box example, adults and children focus on a single activity. This strategy, common in Western middle-SES homes, is well-suited to lessons in which children master skills apart from everyday situations in which they will later use those skills. In contrast, infants and young children in Guatemalan Mayan and other Native American and indigenous communities often attend to several events at once. For example, one 12-month-old skillfully put objects in a jar while watching a passing truck and blowing into a toy whistle (Correa-Chavez, Roberts, & Perez, 2011).

Attending to several competing events simultaneously may be vital in cultures where children learn largely through keen observation of others’ ongoing activities. In a comparison of 18-month-olds from German middle-SES homes and Nso farming villages in Cameroon, the Nso toddlers copied far fewer experimenter-demonstrated actions on toys than did the German toddlers (Borchert et al., 2013). Nso caregivers rarely create such child-focused teaching situations. Rather, they expect children to imitate observed behaviors without adult prompting. Nso children are motivated to do so because they want to be included in the major activities of their community.

By bringing the task within the child’s zone of proximal development and adjusting her communication to suit the child’s needs, a grandmother transfers mental strategies to her granddaughter, promoting her cognitive development.

Earlier we saw how infants and toddlers create new schemes by acting on the physical world (Piaget) and how certain skills become better-developed as children represent their experiences more efficiently and meaningfully (information processing). Vygotsky adds a third dimension to our understanding by emphasizing that many aspects of cognitive development are socially mediated. The Cultural Influences box on page 220 presents additional evidence for this idea, and we will see even more evidence in the next section.

Ask Yourself

Connect ■ List techniques that parents can use to scaffold development of categorization in infancy and toddlerhood, and explain why each is effective.

Apply ■ When Timmy was 18 months old, his mother stood behind him, helping him throw a large ball into a box. As his skill improved, she stepped back, letting him try on his own. Using Vygotsky’s ideas, explain how Timmy’s mother is supporting his cognitive development.

Reflect ■ Describe your earliest autobiographical memory. How old were you when the event occurred? Do your responses fit with research on infantile amnesia?

6.4 INDIVIDUAL DIFFERENCES IN EARLY MENTAL DEVELOPMENT

6.4a Describe the mental testing approach, the meaning of intelligence test scores, and the extent to which infant tests predict later performance.

6.4b Discuss environmental influences on early mental development, including home, child care, and early intervention for at-risk infants and toddlers.

At age 22 months, Timmy had only a handful of words in his vocabulary, played in a less mature way than Caitlin and Grace, and seemed restless and overactive. Worried about Timmy’s progress, Vanessa arranged for a psychologist to give him one of many tests available for assessing mental development in infants and toddlers.

Cultural InfluencesSocial Origins of Make-Believe Play

One of the activities my husband, Ken, used to do with our two young sons was to bake pineapple upside-down cake, a favorite treat. One Sunday afternoon when a cake was in the making, 21-month-old Peter stood on a chair at the kitchen sink, busily pouring water from one cup to another.

“He’s in the way, Dad!” complained 4-year-old David, trying to pull Peter away from the sink.

“Maybe if we let him help, he’ll give us room,” Ken suggested. As David stirred the batter, Ken poured some into a small bowl for Peter, moved his chair to the side of the sink, and handed him a spoon.

“Here’s how you do it, Petey,” instructed David, with a superior air. Peter watched as David stirred, then tried to copy his motion. When it was time to pour the batter, Ken helped Peter hold and tip the small bowl.

“Time to bake it,” said Ken.

“Bake it, bake it,” repeated Peter, watching Ken slip the pan into the oven.

Several hours later, Ken observed one of Peter’s earliest instances of make-believe play. He got his pail from the sandbox and, after filling it with a handful of sand, carried it into the kitchen and put it down on the floor in front of the oven. “Bake it, bake it,” Peter called to Ken. Together, father and son placed the pretend cake in the oven.

Piaget and his followers concluded that toddlers discover make-believe independently, once they are capable of representational schemes. Vygotsky’s theory has challenged this view. He believed that society provides children with opportunities to represent culturally meaningful activities in play. Make-believe, like other complex mental activities, is first learned under the guidance of experts (Meyers & Berk, 2014). In the example just described, Peter extended his capacity to represent daily events when Ken drew him into the baking task and helped him act it out in play.

Current evidence supports the idea that early make-believe is the combined result of children’s readiness to engage in it and social experiences that promote it. In Western middle-SES families, play is culturally cultivated and scaffolded by adults (Gaskins, 2015). Mothers, especially, offer toddlers a rich array of cues that they are pretending—looking and smiling at the child more, making more exaggerated movements, and using more “we” talk (acknowledging that pretending is a joint endeavor) than they do during the same real-life event (Lillard et al., 2007). These cues encourage toddlers to join in and probably facilitate their ability to distinguish pretend from real acts, which strengthens over the second and third years.

When adults participate, toddlers’ make-believe is more elaborate (Keren et al., 2005). They are more likely to combine pretend acts into complex sequences, as Peter did when he put the sand in the bucket (making the batter), carried it into the kitchen, and, with Ken’s help, put it in the oven (baking the cake). The more parents pretend with their toddlers, the more time their children devote to make-believe (Cote & Bornstein, 2009).

In some cultures, such as those of Indonesia and Mexico, where play is viewed as solely a child’s activity and sibling caregiving is common, make-believe is more frequent and more complex with older siblings than with mothers. As early as age 3 to 4, children provide rich, challenging stimulation to their younger brothers and sisters, take these teaching responsibilities seriously, and, with age, become better at them (Lancy, 2014; Zukow-Goldring, 2002). In a study of Zinacanteco Indian children of southern Mexico, by age 8, sibling teachers were highly skilled at showing 2-year-olds how to play at everyday tasks, such as washing and cooking (Maynard, 2002). They often guided toddlers verbally and physically through the task and provided feedback.

As we will see in Chapters 9 and Chapter 10, make-believe play is an important means through which children enhance their cognitive and social skills and learn about important activities in their culture (Nielsen, 2012). Vygotsky’s theory, and the findings that support it, tell us that providing a stimulating physical environment is not enough to promote early cognitive development. In addition, toddlers must be invited and encouraged by more skilled members of their culture to participate in the social world around them. Parents and teachers can enhance early make-believe by playing often with toddlers, guiding and elaborating their make-believe themes.

In cultures where sibling caregiving is common, make-believe play is more frequent and complex with older siblings than with mothers. These Afghan children play “wedding,” dressing the youngest as a bride.

The cognitive theories we have just discussed try to explain the process of development—how children’s thinking changes. Mental tests, in contrast, focus on individual differences: They measure variations in developmental progress, arriving at scores that predict future performance, such as later intelligence and school achievement. This concern with prediction arose over a century ago, when French psychologist Alfred Binet designed the first successful intelligence test, which predicted school achievement (see Chapter 1). It inspired the design of many new tests, including ones that measure intelligence at very early ages.

6.4.1 Infant and Toddler Intelligence Tests

Accurately measuring infants’ intelligence is a challenge because they cannot answer questions or follow directions. All we can do is present them with stimuli, coax them to respond, and observe their behavior. As a result, most infant tests emphasize perceptual and motor responses. But increasingly, tests are being developed that also tap early language, cognition, and social behavior, especially with older infants and toddlers.

One commonly used test, the Bayley Scales of Infant and Toddler Development, is suitable for children between 1 month and 3½ years. The most recent edition, the Bayley-III, has three main subtests: (1) the Cognitive Scale, which includes such items as attention to familiar and unfamiliar objects, looking for a fallen object, and pretend play; (2) the Language Scale, which taps understanding and expressions of language—for example, recognition of objects and people, following simple directions, and naming objects and pictures; and (3) the Motor Scale, which includes gross- and fine-motor skills, such as grasping, sitting, stacking blocks, and climbing stairs (Bayley, 2005).

A trained examiner administers a test based on the Bayley Scales of Infant Development to a 1-year-old in her mother’s lap. Current Bayley-III Cognitive and Language Scales predict preschool mental test performance better than earlier versions.

PHOTO BY STEPHEN AUSMUS/USDA/ARS

Two additional Bayley-III scales depend on parental report: (4) the Social-Emotional Scale, which asks caregivers about such behaviors as ease of calming, social responsiveness, and imitation in play; and (5) the Adaptive Behavior Scale, which asks about adaptation to the demands of daily life, including communication, self-control, following rules, and getting along with others.

Computing Intelligence Test Scores

Intelligence tests for infants, children, and adults are scored in much the same way—by computing an intelligence quotient (IQ), which indicates the extent to which the raw score (number of items passed) deviates from the typical performance of same-age individuals. To make this comparison possible, test designers engage in standardization—giving the test to a large, representative sample and using the results as the standard for interpreting scores. The standardization sample for the Bayley-III included 1,700 infants, toddlers, and young preschoolers, reflecting the U.S. population in SES and ethnic diversity.

Within the standardization sample, performances at each age level form a normal distribution, in which most scores cluster around the mean, or average, with progressively fewer falling toward the extremes (see Figure 6.9). This bell-shaped distribution results whenever researchers measure individual differences in large samples. When intelligence tests are standardized, the mean IQ is set at 100. An individual’s IQ is higher or lower than 100 by an amount that reflects how much his or her test performance deviates from the standardization-sample mean.

The IQ offers a way of finding out whether an individual is ahead, behind, or on time (average) in mental development compared with others of the same age. For example, if Timmy’s score is 100, then he did better than 50 percent of his agemates. A child with an IQ of 85 did better than only 16 percent, whereas a child with an IQ of 130 outperformed 98 percent. The IQs of 96 percent of individuals fall between 70 and 130; only a few achieve higher or lower scores.

Figure 6.9 Normal distribution of intelligence test scores. To determine what percentage of same-age individuals in the population a person with a certain IQ outperformed, add the figures to the left of that IQ score. For example, an 8-year-old child with an IQ of 115 scored better than 84 percent of the population of 8-year-olds.

Predicting Later Performance from Infant Tests

Despite careful construction, most infant tests—including previous editions of the Bayley—predict later intelligence poorly. Infants and toddlers easily become distracted, fatigued, or bored during testing, so their scores often do not reflect their true abilities. And infant perceptual and motor items differ from the tasks given to older children, which increasingly emphasize verbal, conceptual, and problem-solving skills. In contrast, the Bayley-III Cognitive and Language Scales, which better dovetail with childhood tests, are good predictors of preschool mental test performance (Albers & Grieve, 2007; Bode et al., 2014). But because most infant test scores do not tap the same dimensions of intelligence measured at older ages, they usually are conservatively labeled developmental quotients (DQs) rather than IQs.

Infant tests are somewhat better at making long-term predictions for extremely low-scoring babies. Today, they are largely used for screening—helping to identify for further observation and intervention babies who are likely to have developmental problems.

As an alternative to infant tests, some researchers have turned to information-processing measures, such as habituation, to assess early mental progress. Their findings show that speed of habituation and recovery to novel visual stimuli are among the best available infant predictors of IQ from early childhood to early adulthood, with correlations ranging from the.30s to the.60s (Fagan, Holland, & Wheeler, 2007; Kavšek, 2004). Habituation and recovery seem to be an especially effective early index of intelligence because they assess memory as well as quickness and flexibility of thinking, which underlie intelligent behavior at all ages (Colombo et al., 2004). The consistency of these findings has prompted designers of the Bayley-III to include items that tap such cognitive skills as habituation, object permanence, and categorization.

6.4.2 Early Environment and Mental Development

In Chapter 2, we indicated that intelligence is a complex blend of hereditary and environmental influences. As we consider evidence on the relationship of environmental factors to infant and toddler mental test scores, you will encounter findings that highlight the role of heredity as well.

Home Environment

The Home Observation for Measurement of the Environment (HOME) is a checklist for gathering information about the quality of children’s home lives through observation and parental interview (Caldwell & Bradley, 1994). Applying What We Know on the following page lists the factors measured by the HOME Infant–Toddler Subscales—the most widely used home environment measure during the first three years. A briefer, exclusively observational HOME instrument is also available (Rijlaarsdam et al., 2012).

Each HOME subscale is positively related to toddlers’ mental test performance. Furthermore, within diverse SES and ethnic groups, an organized, stimulating physical setting and parental affection, involvement, and encouragement of new skills repeatedly predict better language and IQ scores in toddlerhood and early childhood (Bornstein, 2015; Fuligni, Han, & Brooks-Gunn, 2004; Linver, Martin, & Brooks-Gunn, 2004; Ronfani et al., 2015; Tong et al., 2007). The extent to which parents talk to infants and toddlers is particularly important. It contributes strongly to early language progress, which, in turn, predicts intelligence and academic achievement in elementary school (Hart & Risley, 1995; Hoff, 2013).

Yet we must interpret these correlational findings cautiously. In all the studies, children were reared by their biological parents, with whom they share not just a common environment but also a common heredity. Parents who are genetically more intelligent may provide better experiences while also giving birth to genetically brighter children, who evoke more stimulation from their parents. Research supports this hypothesis, which refers to gene–environment correlation (see pages 80–81 in Chapter 2) (Hadd & Rodgers, 2017; Saudino & Plomin, 1997). But parent–child shared heredity does not account for the entire association between home environment and mental test scores. Family living conditions—both HOME scores and affluence of the surrounding neighborhood—continue to predict children’s IQ beyond the contribution of parental IQ and education (Chase-Lansdale et al., 1997; Klebanov et al., 1998).

A father plays actively with his baby. Parental warmth, attention, and verbal communication predict better language and IQ scores in toddlerhood and early childhood.

Applying What We Know

Features of a High-Quality Home Life for Infants and Toddlers: The HOME Infant–Toddler Subscales

Home Subscale

Sample Item

Organization of the physical environment

Child’s play environment appears safe and free of hazards.

Provision of appropriate play materials

Parent provides toys or interesting activities for child during observer’s visit.

Emotional and verbal responsiveness of the parent

Parent caresses or kisses child at least once during observer’s visit.

Parent spontaneously speaks to child twice or more (excluding scolding) during observer’s visit.

Parental acceptance of the child

Parent does not interfere with child’s actions or restrict child’s movements more than three times during observer’s visit.

Parental involvement with the child

Parent tends to keep child within view and to look at child often during observer’s visit.

Opportunities for variety in daily stimulation

Child eats at least one meal per day with mother and/or father, according to parental report.

Child frequently has a chance to get out of house (for example, accompanies parent on trips to grocery store).

Sources: Bradley, 1994; Bradley et al., 2001. A brief, exclusively observational HOME instrument taps the first three subscales only (Rijlaarsdam et al., 2012).

How can the research summarized so far help us understand Vanessa’s concern about Timmy’s development? Ben, the psychologist who tested Timmy, found that he scored only slightly below average. Ben talked with Vanessa about her child-rearing practices and watched her play with Timmy. A single parent who worked long hours, Vanessa had little energy for Timmy at the end of the day. Ben also noticed that Vanessa, anxious about Timmy’s progress, was intrusive: She interfered with his active behavior and bombarded him with directions: “That’s enough ball play. Stack these blocks.”

Children who experience intrusive parenting are likely to be distractible and withdrawn and do poorly on mental tests—negative outcomes that persist unless parenting improves (Clincy & Mills-Koonce, 2013; Rubin, Coplan, & Bowker, 2009). Ben coached Vanessa in how to interact sensitively with Timmy while assuring her that responsive parenting that builds on toddlers’ current capacities is a much better indicator of how children will do later than an early mental test score.

Infant and Toddler Child Care

Today, about 60 percent of U.S. mothers with a child under age 2 are employed (U.S. Bureau of Labor Statistics, 2018). Child care for infants and toddlers has become common, and its quality—though not as influential as parenting—affects mental development.

With support from their caregivers, toddlers at a child-care center in Leipzig, Germany, explore the look and feel of colorful paints. High-quality child care—a generous caregiver–child ratio, well-trained caregivers, and developmentally appropriate activities—benefits children of all SES levels, especially those from low-SES homes.

WALTRAUDÂ GRUBITZSCH/picture alliance/Getty Images

Research consistently shows that young children exposed to poor-quality child care—whether they come from middle- or low-SES homes—score lower on measures of cognitive, language, academic, and social skills during the preschool, elementary, and secondary school years (Belsky et al., 2007b; Burchinal et al., 2015; Dearing, McCartney, & Taylor, 2009; NICHD Early Child Care Research Network, 2000b, 2001, 2003b, 2006; Vandell et al., 2010). In contrast, good child care can reduce the negative impact of a stressed, poverty-stricken home life and it sustains the benefits of growing up in an economically advantaged family (Burchinal, Kainz, & Cai, 2011; McCartney et al., 2007). As Figure 6.10 illustrates, the Early Childhood Longitudinal Study—consisting of a large sample of U.S. children diverse in SES and ethnicity followed from birth through the preschool years (see page 42 in Chapter 1)—confirmed the importance of continuous high-quality child care from infancy through the preschool years (Li et al., 2013).

Unlike child care in most European countries and Australia and New Zealand, which is nationally regulated and funded to ensure its quality, child care in the United States raises serious concerns. Standards are set by the individual states and vary widely. In studies of quality, only 20 to 25 percent of child-care centers and family child-care homes provided infants and toddlers with sufficiently positive, stimulating experiences to promote healthy psychological development. Most settings offered substandard care (NICHD Early Child Care Research Network, 2000a, 2004). And the cost of child care in the United States is high: On average, full-time center-based care for one infant consumes 15 percent of the median income for couples and 50 percent for single parents (Child Care Aware, 2017). The cost of a family child-care home is about two-thirds of center-based care.

Figure 6.10 Relationship of child-care quality in infancy–toddlerhood and the preschool years to language development at age 5. When a nationally representative sample of more than 1,300 children was followed over the first five years, language scores were highest for those experiencing high-quality child care in both infancy–toddlerhood and the preschool years, intermediate for those experiencing high-quality care in just one of these periods, and lowest for those experiencing poor-quality care in both periods. Cognitive, literacy, and math scores also showed this pattern. (Based on Li et al., 2013.)

Unfortunately, many U.S. children from low-income families experience inadequate child care (Torquati et al., 2011). But U.S. settings providing the very worst care tend to serve middle-income families. These parents are especially likely to place their children in for-profit centers, where quality tends to be lowest. Economically disadvantaged children more often attend publicly subsidized, nonprofit centers, which are better equipped with learning materials and have smaller group sizes and more favorable teacher–child ratios (Johnson, Ryan, & Brooks-Gunn, 2012), Still, many low-income children experience substandard child care.

See Applying What We Know on the following page for signs of high-quality child care for infants and toddlers based on standards for developmentally appropriate practice devised by the U.S. National Association for the Education of Young Children. These standards specify program characteristics that serve young children’s developmental and individual needs, based on both current research and consensus among experts.

Child care in the United States is affected by a macrosystem of individualistic values and weak government regulation and funding. Furthermore, many parents think that their children’s child-care experiences are better than they really are (Torquati et al., 2011). Unable to identify good care or without the financial means to purchase it, they do not demand it. In recent years, the U.S. federal government and some states have allocated additional funds to subsidize child-care costs, especially for low-income families (Matthews, 2014). Though far from meeting the need, this increase in resources has had a positive impact on child-care quality and accessibility.

Look and Listen

Ask several employed parents of infants or toddlers to describe what they sought in a child-care setting, along with challenges they faced in finding child care. How knowledgeable are the parents about the ingredients of high-quality care?

6.4.3 Early Intervention for At-Risk Infants and Toddlers

Children living in persistent poverty are likely to show gradual declines in intelligence test scores and to achieve poorly when they reach school age (Schoon et al., 2012b). These problems are largely due to stressful home environments that undermine children’s ability to learn and increase the likelihood that they will remain poor as adults. A variety of intervention programs have been developed to break this tragic cycle of poverty. Although most begin during the preschool years (we will discuss these in Chapter 9), some start during infancy and continue through early childhood.

Applying What We Know

Signs of Developmentally Appropriate Infant and Toddler Child Care

Program Characteristic

Signs of Quality

Physical setting

Indoor environment is clean, in good repair, well-lighted, and well-ventilated. Fenced outdoor play space is available. Setting does not appear overcrowded when children are present.

Toys and equipment

Play materials are appropriate for infants and toddlers and are stored on low shelves within easy reach. Cribs, highchairs, infant seats, and child-sized tables and chairs are available. Outdoor equipment includes small riding toys, swings, slide, and sandbox.

Caregiver–child ratio

In child-care centers, caregiver–child ratio is no greater than 1 to 3 for infants and 1 to 6 for toddlers. Group size (number of children in one room) is no greater than 6 infants with two caregivers and 12 toddlers with two caregivers. In family child-care homes, caregiver is responsible for no more than 6 children; within this group, no more than 2 are infants or toddlers. Staffing is consistent, so infants and toddlers can form relationships with particular caregivers.

Daily activities

Daily schedule includes times for active play, quiet play, naps, snacks, and meals. It is flexible rather than rigid, to meet the needs of individual children. Atmosphere is warm and supportive, and children are never left unsupervised.

Interactions among adults and children

Caregivers respond promptly to infants’ and toddlers’ distress; hold, talk to, sing, and read to them; and interact with them in a manner that respects the individual child’s interests and tolerance for stimulation.

Caregiver qualifications

Caregiver has some training in child development, first aid, and safety.

Relationships with parents

Parents are welcome anytime. Caregivers talk frequently with parents about children’s behavior and development.

Licensing and accreditation

Child-care setting, whether a center or a home, is licensed by the state. In the United States, voluntary accreditation by the National Association for the Education of Young Children, www.naeyc.org/accreditation, or the National Association for Family Child Care, www.nafcc.org, is evidence of an especially high-quality program.

Source: Copple & Bredekamp, 2009.

In center-based interventions, children attend an organized child-care or preschool program where they receive educational, nutritional, and health services, and their parents receive child-rearing and other social service supports. In home-based interventions, a skilled adult visits the home and works with parents, providing social support and teaching them how to stimulate a young child’s development. In most programs of either type, participating children score higher than untreated controls on mental tests by age 2. The earlier intervention begins, the longer it lasts, and the greater its scope and intensity (for example, year-round high-quality child care plus generous support services for parents), the better participants’ cognitive and academic performance throughout childhood and adolescence (Ramey, Ramey, & Lanzi, 2006).

The Carolina Abecedarian Project illustrates these positive outcomes. In the 1970s, more than 100 infants from poverty-stricken families, ranging in age from 3 weeks to 3 months, were randomly assigned to either a treatment group or a control group. Treatment infants were enrolled in full-time, year-round child care through the preschool years. There they received carefully planned educational experiences aimed at promoting motor, cognitive, language, and social skills and, after age 3, literacy and math concepts. Special emphasis was placed on rich, responsive adult–child verbal communication. All children received nutrition and health services; the primary difference between treatment and controls was the intensive child-care experience.

As Figure 6.11 shows, by 12 months of age, the IQs of the two groups diverged. Treatment children sustained an advantage until last tested—at age 21. In addition, throughout their years of schooling, treatment youths achieved considerably higher scores in reading and math. These gains translated into reduced enrollment in special education, more years of schooling completed, higher rates of college enrollment and employment in skilled jobs, and lower rates of drug use and adolescent parenthood (Campbell & Ramey, 2010; Campbell et al., 2001, 2002, 2012).

Recognition of the power of intervening as early as possible led the U.S. Congress to provide limited funding for intervention services directed at infants and toddlers who already have serious developmental problems or who are at risk for problems because of poverty. Early Head Start, begun in 1995, currently has 1,000 sites serving about 110,000 low-income children and their families (Walker, 2014). It offers an array of coordinated services—child care, educational experiences for infants and toddlers, parenting education, family social support, and health care—delivered through a center-based, home-based, or mixed approach, depending on community needs.

Figure 6.11 IQ scores of treatment and control children from infancy to 21 years in the Carolina Abecedarian Project. At 1 year of age, treatment children outperformed controls, an advantage consistently maintained through age 21. The IQ scores of both groups declined gradually during childhood and adolescence—a trend probably due to the damaging impact of poverty on mental development. (Based on Campbell et al., 2001.)

An evaluation, conducted when children reached age 3, showed that Early Head Start led to warmer, more supportive and stimulating parenting, a reduction in harsh discipline, gains in cognitive and language development, and lessening of child aggression (Love, Chazan-Cohen, & Raikes, 2007; Love et al., 2005; Paschall & Mastergeorge, 2018; Raikes et al., 2010). Also, Early Head Start offered some protection from the negative effects of parental insensitivity, which led to less harmful outcomes among children in the program than among no-intervention controls (Ayoub et al., 2014). The strongest effects occurred at sites mixing center- and home-visiting services.

By age 5, however, most benefits of Early Head Start had declined or disappeared, and a follow-up in fifth grade showed no persisting cognitive gains (U.S. Department of Health and Human Services, 2006; Vogel et al., 2010). One speculation is that more intentional educational experiences extending through the preschool years—as in the Abecedarian project—would increase the lasting impact of Early Head Start (Barnett, 2011). Also, some evidence suggests that the cognitive benefits of Early Head Start are greater for certain children—in particular, those who receive little stimulation at home (Bradley, McKelvey, & Whiteside-Mansell, 2011). Although Early Head Start is in need of refinement, it is a promising beginning at providing U.S. infants and toddlers living in poverty with publicly supported intervention.

This Early Head Start program provides rich, educational experiences for toddlers plus parent education and family social supports. The most favorable outcomes of Early Head Start result from mixing center- and home-visiting services.

Ask Yourself

Connect ■ Using what you learned about brain development in Chapter 5, explain why it is best to initiate intervention for children living in poverty in the first two years rather than later.

Apply ■ Fifteen-month-old Joey’s developmental quotient (DQ) is 115. His mother wants to know exactly what this means and what she should do to support his intellectual development. How would you respond?

Reflect ■ Suppose you were seeking a child-care setting for your baby. What would you want it to be like, and why?

6.5 LANGUAGE DEVELOPMENT

6.5a Describe theories of language development, and indicate the emphasis each places on innate abilities and environmental influences.

6.5b Describe major language milestones in the first two years, individual and cultural differences, and ways adults can support early language development.

Advances in perception and cognition during infancy pave the way for an extraordinary human achievement—language. In Chapter 5, we saw that by the second half of the first year, infants make dramatic progress in distinguishing the basic sounds of their language and in segmenting the flow of speech into word and phrase units. They also start to comprehend some word meanings and, around 12 months of age, say their first word. Sometime between 1½ and 2 years, toddlers combine two words (MacWhinney, 2015). By age 6, children understand the meaning of about 14,000 words, speak in elaborate sentences, and are skilled conversationalists.

To appreciate this awesome task, think about the many abilities involved in your own flexible use of language. When you speak, you must select words that match the underlying concepts you want to convey. To be understood, you must pronounce words correctly. Then you must combine them into phrases and sentences using a complex set of grammatical rules. Finally, you must follow the rules of everyday conversation, taking turns, making comments relevant to what your partner just said, and using an appropriate tone of voice.

How do infants and toddlers make such remarkable progress in launching these skills? To address this question, let’s examine several prominent theories of language development.

6.5.1 Theories of Language Development

In the 1950s, researchers did not take seriously the idea that very young children might be able to figure out important properties of language. Children’s regular and rapid attainment of language milestones suggested a process largely governed by maturation, inspiring the nativist perspective on language development. In recent years, new evidence has spawned the interactionist perspective, which emphasizes the joint roles of children’s inner capacities and communicative experiences.

The Nativist Perspective

According to linguist Noam Chomsky’s (1957) nativist theory, language is a uniquely human accomplishment, etched into the structure of the brain. Focusing on grammar, Chomsky reasoned that the rules of sentence organization are too complex to be directly taught to or discovered by even a cognitively sophisticated young child. Rather, he proposed that all children have a language acquisition device (LAD), an innate system that contains a universal grammar, or set of rules common to all languages. It enables children, no matter which language they hear, to understand and speak in a rule-oriented fashion as soon as they pick up enough words.

Infants communicate from the very beginning of life. How will this child become a fluent speaker of her native language within just a few years? Theorists disagree sharply.

Are children innately primed to acquire language? Recall from Chapter 4 that newborn babies are remarkably sensitive to speech sounds. And children everywhere attain major language milestones in a similar sequence (Parish-Morris, Golinkoff, & Hirsh-Pasek, 2013). Also, the ability to master a grammatically complex language system seems to be unique to humans, as efforts to teach language to nonhuman primates—using either specially devised artificial symbol systems or sign language—have met with only limited success. Even after extensive training, chimpanzees (who are closest to humans in terms of evolution) master only a basic vocabulary and short word combinations, and they produce these combinations far less consistently than human preschoolers do (Tomasello, Call, & Hare, 2003).

Evidence for specialized language areas in the brain and a sensitive period for language development have also been interpreted as supporting Chomsky’s theory. Let’s take a closer look at these findings.

Language Areas in the Brain

Recall from Chapter 5 that for most individuals, language is housed largely in the left hemisphere of the cerebral cortex. Within it are two important language-related structures (see Figure 6.12 on page 228). To clarify their functions, researchers have, for several decades, studied adults who experienced damage to these structures and display aphasias, or communication disorders. Broca’s area, located in the left frontal lobe, supports grammatical processing and language production. Wernicke’s area, located in the left temporal lobe, plays a role in comprehending word meaning.

But brain-imaging research suggests that the relationship between these brain structures and language functions is complicated. Neither area is solely, or even mainly, responsible for specific language capacities (Ardila, Bernal, & Rosselli, 2016). Furthermore, the impaired pronunciation and grammar of patients with Broca’s aphasia and the meaningless speech streams of patients with Wernicke’s aphasia involve the spread of injury from those areas to nearby cortical areas. In addition, the brain damage triggers widespread abnormal activity elsewhere in the left cerebral hemisphere (Bates et al., 2003; Keller et al., 2009).

The broad association of language functions with left-hemispheric regions is consistent with Chomsky’s notion of a brain prepared to process language. But critics point out that at birth, the brain is not fully lateralized; it is highly plastic. Language areas in the cerebral cortex develop as children acquire language (Bishop et al., 2014; Mills & Conboy, 2005). Although the left hemisphere is biased for language processing, if it is injured in the first few years, other regions take over language functions, and most affected children eventually attain typical language competence. Thus, left-hemispheric localization, though the norm, is not necessary for effective language processing.

Nevertheless, when the young brain allocates language to the right hemisphere—as a result of left-hemispheric damage or the learning of sign language (see pages 160–161 in Chapter 5)—it localizes it in roughly the same regions that typically support language in the left hemisphere (Stiles, Reilly, & Levine, 2012). This suggests that those brain structures are uniquely disposed for language processing.

Figure 6.12 Broca’s and Wernicke’s areas, in the left hemisphere of the cerebral cortex. Broca’s area, located in the frontal lobe, supports grammatical processing and language production. Wernicke’s area, located in the temporal lobe, is involved in comprehending word meaning. Contrary to what was once believed, however, neither area is solely or even mainly responsible for these functions.

A Sensitive Period for Language Development

Must language be acquired early in life, during an age span in which the brain is particularly responsive to language stimulation? Evidence for a sensitive period would support the view that language development has unique biological properties.

To test this idea, researchers examined the language competence of deaf adults who acquired their first language—American Sign Language (ASL), a gestural system just as complex as any spoken language—at different ages. The later learners, whose hearing parents chose to educate them through the oral method, which relies on speech and lip-reading, acquired little spoken language because of their profound deafness. Consistent with the sensitive-period notion, those who learned ASL in adolescence or adulthood never became as proficient, especially at ASL grammar, as those who learned it in childhood (Mayberry, 2010; Singleton & Newport, 2004).

The age at which children with hearing impairment start receiving language input emerges repeatedly in research as a powerful influence on language outcomes. Deaf children of deaf parents, who from birth were exposed to rich language stimulation through sign language, show typical language progress. Among hearing impaired children of hearing parents, language development depends on the age at which they were fitted with an effective hearing device—either a hearing aid or a cochlear implant, an electronic mechanism surgically inserted into the ear that converts sounds into signals to stimulate the auditory nerve. In one series of studies, children born with limited or no hearing showed typical mastery of complex grammatical structures in middle childhood only if they were exposed to language input during the first year of life after receiving such a device (Friedmann & Haddad-Hanna, 2014; Friedmann & Szterman, 2011; Szterman & Friedmann, 2014). In contrast, children who lost their hearing after their first year and were fitted with hearing devices at varying later ages showed no difficulties with grammatical development (Friedmann & Rusou, 2015).

Biology and EnvironmentThiamine Deficiency in the First Year and Later Language Impairment

Thiamine (vitamin B1) is essential for normal brain development and functioning, including synapse formation, production of neurotransmitters, myelination, and maintenance of neuronal structures. Because the body continuously uses available thiamine, storing it only briefly, adults show central nervous system symptoms—poor memory, sleep difficulties, mental confusion, vision problems, and muscle cramps and weakness—after just two to three weeks of dietary thiamine deficiency, recovering if adequate thiamine is soon restored (Kloss, Eskin, & Suh, 2018). Insufficient thiamine intake also affects the infant brain, though symptoms are difficult to recognize and often confused with indicators of other diseases.

Vitamin enrichment of basic foods has made thiamine deficiency rare, except in poverty-stricken regions of the world with food shortages (Hiffler et al., 2016). Errors in food enrichment, however, can cause widespread deficiency, even in nations with plentiful, healthy food.

In 2003, a manufacturer in Israel mistakenly released a defective infant formula, failing to include in it a thiamine additive. An estimated 600 to 1,000 infants regularly consumed the formula. Though many showed no neurological symptoms, they were nevertheless considered high-risk for developmental problems and monitored over time. As they reached 2 to 3 years of age, an evaluation of 20 children revealed substantial delays in language comprehension and production (Fattal-Valevski et al., 2009).

A subsequent follow-up of 59 affected children at age 5 to 7 examined complex language skills (Fattal, Friedmann, & Fattal-Valevski, 2011). The researchers assessed mastery of grammatical structures in several ways. For example, the children were asked to select from pairs of pictures the one that matched the meaning of sentences containing relative clauses (see Figure 6.13 for an example). They were also asked to repeat sentences with intricate grammatical structures (such as, “Which teacher does the boy like?”), a challenging task that requires both understanding of each structure and the ability to produce it. Furthermore, to assess vocabulary recall, the children had to label pictures that depicted various word classes, including objects, object parts, adjectives, verbs, adverbs, and prepositions.

Results revealed that 97 percent of children who had been thiamine-deficient in their first year displayed language deficits in grammar, vocabulary recall, or both, even though their thiamine intake had been adequate from toddlerhood on. In contrast, same-age controls, recruited from the same communities as the thiamine-deficient children, performed well: Only 9 percent displayed language deficits, the same rate as in the general population.

The thiamine-deficient children attained typical scores on the Bayley Scales (with the exception of language) at age 2 to 3 and on assessments of conceptual understanding at 5 to 7. Therefore, their language impairment could not be attributed to low intelligence.

Thiamine deficiency in adulthood, after brain development is complete, does not affect language abilities (Sechi et al., 2016). But when thiamine is lacking in infancy, its impact on language persists, seriously impairing children’s grammatical and word recall skills. These findings support the conclusion that the first year of life is a sensitive period for development of brain structures crucial for acquiring language.

Figure 6.13 An example of a pair of pictures used in the relative-clause comprehension task. A relative clause has a subject and verb that elaborate on the noun that precedes them, as in “Show me the girl that the woman is drawing.” The child was shown a pair of pictures and asked to point to the one that matches the meaning of this sentence. (From I. Fattal, N. Friedman, & A. Fattal-Valevski, 2011, “The Crucial Role of Thiamine in the Development of Syntax and Lexical Retrieval: A Study of Infantile Thiamine Deficiency,” Brain, 134, p. 1725. Copyright © 2011 Oxford University Press. Reprinted by permission.)

These findings suggest that infancy is a sensitive period for acquiring grammar, even though infants are not yet able to understand and produce sentences. Some researchers speculate that capacities evident in infancy, such as statistical learning of native-language speech units (see page 175 in Chapter 5), combined with the young brain’s openness to detecting those units, may be vital for later mastery of grammar (Thiessen, Girard, & Erickson, 2016). The importance of the first year for later language proficiency is also evident in children who suffered from an early dietary deficiency that is crucial for brain development, as the Biology and Environment box above reveals.

Is acquiring a second language also harder after a sensitive period has passed? In several studies, researchers selected immigrants from non-English-speaking countries who had resided in the United States for at least six years, to ensure that they had accomplished most of their English learning. As age of immigration increased from infancy and early childhood into adulthood, proficiency in both English pronunciation and grammar declined (Hakuta, Bialystok, & Wiley, 2003; Huang, 2014). Furthermore, ERP and fMRI measures of brain activity indicate that second-language processing is less lateralized in older than in younger learners (Neville & Bruer, 2001). However, second-language competence does not drop sharply at a certain age. Rather, a continuous, age-related decrease occurs.

In sum, research on both first- and second-language learning reveals a biologically based timeframe for optimum language development. However, the boundaries of the sensitive period for second language learning remain unclear.

Limitations of the Nativist Perspective

Chomsky’s theory has had a major impact on current views of language development. It is now widely accepted that humans have a unique, biologically based capacity to acquire language. Still, the theory has been contested on several grounds.

First, researchers have had great difficulty specifying Chomsky’s universal grammar. A major problem is the absence of a complete description of these abstract grammatical rules or even an agreed-on list of how many exist or the best examples of them. Chomsky’s critics doubt that one set of rules can account for the extraordinary variation in grammatical forms among the world’s 5,000 to 8,000 languages (Cole, Hermon, & Yanti, 2015; Dabrowska, 2015). How children manage to link such rules with the strings of words they hear is also unclear.

An Ethiopian father attends an English-as-a-second-language class with his daughter. Evidence that second-language proficiency declines with age suggests that he will never be as proficient an English speaker as she will.

Mike Greenlar | The Post Standard

Second, Chomsky’s assumption that grammatical knowledge is innately determined does not fit with certain observations of language development. Once children begin to use an innate grammatical structure, we would expect them to apply it to all relevant instances in their language. But children refine and generalize many grammatical forms gradually, engaging in much piecemeal learning and making errors along the way (Evans & Levinson, 2009; MacWhinney, 2015). For example, one 3-year-old, in grappling with prepositions, initially added with to the verb open (“You open with scissors”) but not to the verb hit (“He hit me stick”) (Tomasello, 2006). As we will see in Chapter 12, complete mastery of some grammatical forms, such as the passive voice, is not achieved until well into middle childhood. This suggests that more experimentation and learning are involved than Chomsky assumed.

The Interactionist Perspective

Recent ideas about language development emphasize interactions between inner capacities and environmental influences. One type of interactionist theory applies the information-processing perspective to language development. A second type emphasizes social interaction.

Some information-processing theorists assume that children make sense of their complex language environments by applying powerful cognitive capacities of a general kind (Joanisse & McClelland, 2015; MacWhinney, 2015; Samuelson & McMurray, 2017). These theorists note that regions of the brain housing language also govern similar perceptual and cognitive abilities, such as the capacity to analyze musical and visual patterns (Saygin, Leech, & Dick, 2010).

Other theorists blend this information-processing view with Chomsky’s nativist perspective. They argue that general cognitive capacities probably are not sufficient to account for mastery of higher-level aspects of language, such as intricate grammatical structures (Aslin & Newport, 2012). They also point out that grammatical competence may depend more on specific brain structures than the other components of language. When 2- to 2½-year-olds and adults listened to short sentences—some grammatically correct, others with grammatical errors—both groups showed similarly distinct ERP brain-wave patterns for each sentence type in the left frontal and temporal lobes of the cerebral cortex (Oberecker & Friederici, 2006). This suggests that 2-year-olds process sentence structures using the same neural system as adults do.

Still other interactionists emphasize that children’s social skills and language experiences are centrally involved in language development. In this social-interactionist view, an active child strives to communicate, which cues her caregivers to provide appropriate language experiences. These experiences, in turn, help the child relate the content and structure of language to its social meanings (Bohannon & Bonvillian, 2013; Chapman, 2006).

Social interactionists disagree over whether or not children are equipped with specialized language structures (Hsu, Chater, & Vitányi, 2013; Lidz, 2007; Tomasello, 2006). Nevertheless, as we chart the course of language development, we will encounter much support for their shared central premise—that children’s social competencies and language experiences greatly affect their language progress. In reality, native endowment, cognitive-processing strategies, and social experience probably operate in different balances with respect to each aspect of language: pronunciation, vocabulary, grammar, and communication skills. Table 6.3 provides an overview of early language milestones that we will examine in the next few sections.

Table 6.3 Milestones of Language Development During the First Two Years

Approximate Age

Milestone

2 months

Infants coo, making pleasant vowel sounds.

4 months on

Infants observe with interest as the caregiver plays turn-taking games, such as pat-a-cake and peekaboo.

6 months on

Infants babble, adding consonants to their cooing sounds and repeating syllables. By 7 months, babbling starts to include many sounds of spoken languages.

Infants begin to comprehend a few commonly heard words.

8–12 months

Infants become more accurate at establishing joint attention with the caregiver, who often verbally labels what the baby is looking at.

Infants actively participate in turn-taking games, trading roles with the caregiver.

Infants use preverbal gestures, such as showing and pointing, to influence others’ goals and behavior and to convey information.

12 months

Babbling includes sound and intonation patterns of the child’s language community.

Speed and accuracy of word comprehension increase rapidly.

Toddlers say their first recognizable word.

18–24 months

Spoken vocabulary expands from about 50 words to 200–250 words.

Toddlers combine two words.

6.5.2 Getting Ready to Talk

Before babies say their first word, they make impressive progress toward understanding and speaking their native tongue. They listen attentively to human speech, and they make speechlike sounds. As adults, we can hardly help but respond.

Cooing and Babbling

Around 2 months, babies begin to make vowel-like noises, called cooing because of their pleasant “oo” quality. Gradually, consonants are added, and around 6 months babbling appears, in which infants repeat consonant–vowel combinations. With age, they increasingly babble in long strings, such as “bababababa” or “nanananana,” perhaps to gain control over producing particular sounds (Fagan, 2015).

Babies everywhere (even those who are deaf) start babbling at about the same age and produce a similar range of early sounds. But for babbling to develop further, infants must be able to hear human speech. In hearing-impaired babies, these speechlike sounds are greatly delayed and limited in diversity of sounds (Bass-Ringdahl, 2010). And a deaf infant not exposed to sign language will stop babbling entirely (Oller, 2000). As we saw in our discussion of a sensitive period, if language input is not restored in the first year, children remain substantially behind in language development.

Even babies who are deaf begin babbling at around 2 months. Those exposed to sign language from birth, as this child has been, babble with their hands, much as hearing babies do through speech.

Babies initially produce a limited number of sounds and then expand to a much broader range. Around 7 months, babbling starts to include many sounds of spoken languages. As caregivers respond to infant babbles, older infants modify their babbling to include sound patterns like those in the adult’s speech. And at 8 to 10 months, infants shift their gaze from the eyes to the mouth of an adult speaker and try to match the speaker’s oral movements (de Boisferon et al., 2017; Diepstra et al., 2017). On hearing this more mature babbling, mothers increase their responsiveness, imitating babbles and labeling objects the baby is looking at even more (Albert, Schwade, & Goldstein, 2018). Around this time, infant babbling reflects the sound and intonation patterns of the baby’s language community—an attainment that predicts the timing of first spoken words (Boysson-Bardies & Vihman, 1991; McGillion et al., 2017).

The next time you hear an older baby babbling, notice how certain sounds appear in particular contexts—for example, when the child is exploring objects, looking at books, or walking upright (Blake & Boysson-Bardies, 1992). Infants seem to be experimenting with the sound system and meaning of language, using parental feedback to acquire native-language forms. Toddlers continue babbling for four or five months after they say their first words.

Deaf infants exposed to sign language from birth babble with their hands much as hearing infants do through speech (Petitto & Marentette, 1991). Furthermore, hearing babies of deaf, signing parents produce babblelike hand motions with the rhythmic patterns of natural sign languages (Petitto et al., 2001, 2004). This sensitivity to language rhythm—evident in both spoken and signed babbling—supports both discovery and production of meaningful language units.

Becoming a Communicator

At birth, infants are prepared for some aspects of conversational behavior. For example, newborns initiate interaction through eye contact and terminate it by looking away. By 3 to 4 months, infants start to gaze in the same general direction adults are looking—a skill that becomes more accurate at 10 to 11 months, as babies realize that others’ focus offers information about their communicative intentions (to talk about an object) or other goals (to obtain an object) (Brooks & Meltzoff, 2005; Senju, Csibra, & Johnson, 2008). Around their first birthday, infants realize that a person’s visual gaze signals a vital connection between the viewer and his or her surroundings, and they want to participate.

This joint attention, in which the child attends to the same object or event as the caregiver, who often labels it, contributes importantly to early language development. Infants and toddlers who frequently experience it sustain attention to named objects longer, comprehend more language, produce meaningful gestures and words earlier, and show faster vocabulary development through 2 years of age (Brooks & Meltzoff, 2008; Flom & Pick, 2003; Yu, Suanda, & Smith, 2019). Gains in joint attention at the end of the first year enable babies to establish a “common ground” with the adult, through which they can figure out the meaning of the adult’s verbal labels.

Around 2 to 3 months, interactions between caregivers and babies begin to include give-and-take. Infants and mothers mutually imitate the pitch, loudness, and duration of each other’s sounds, with mothers taking the lead, imitating about twice as often as infants (Gratier & Devouche, 2011). Between 4 and 6 months, imitation extends to social games, as in pat-a-cake and peekaboo. At first, the parent starts the game and the baby is an amused observer. Gradually, infants join in. By 12 months, infants participate actively, trading roles with the caregiver. Through these imitative exchanges, babies practice the turn-taking pattern of human conversation, a vital context for acquiring language.

At the end of the first year, infants use preverbal gestures to direct adults’ attention, influence their behavior, and convey helpful information (Tomasello, Carpenter, & Liszkowski, 2007). For example, Caitlin held up a toy to show it, pointed to the cupboard when she wanted a cookie, and pointed at her mother’s car keys lying on the floor. Carolyn responded to these gestures and also labeled them (“That’s your bear!” “You want a cookie!” “Oh, there are my keys!”). In this way, toddlers learn that using language leads to desired results.

Besides using preverbal gestures to serve their own goals, 12-month-olds adapt these gestures to the needs of others. In one study, they pointed more often to an object whose location a searching adult did not know than to an object whose location the adult did know (Liszkowski, Carpenter, & Tomasello, 2008). They also understand what an adult means when she points to the location of a hidden toy (Behne et al., 2012). Already, the cooperative processes essential for effective communication are under way—namely, modifying messages to suit others’ intentions and knowledge and recognizing when others have done the same.

This baby uses a preverbal gesture to direct his father’s attention. The father’s verbal response (“I see that squirrel!”) promotes the baby’s transition to spoken language.

The more time caregivers and infants spend in joint activity with objects, the earlier and more often babies use preverbal gestures (Salomo & Liszkowski, 2013). Over time, some of these gestures become explicitly symbolic. For example, a toddler might flap her arms to indicate “butterfly” or raise her palms to signal “all gone.” Soon toddlers integrate words with gestures, using the gesture to expand their verbal message, as in pointing to a toy while saying “give” (Capirci et al., 2005). Gradually, gestures recede, and words become dominant. But the greater the number of items toddlers gesture about and the earlier they form word–gesture combinations, the faster their vocabulary growth, the sooner toward the end of the second year they begin to produce two-word utterances, and the more complex their sentences are at age 3½ (Rowe & Goldin-Meadow, 2009).

Look and Listen

Observe a toddler for 30 to 60 minutes at home or in child care. Jot down preverbal gestures, words, and word–gesture combinations that the baby produces. Do the toddler’s language skills fit with research findings?

6.5.3 First Words

In the middle of the first year, infants begin to understand word meanings; for example, they respond to their own name and, on hearing the words “Mommy” or “Daddy,” look longer at the named parent (Luche et al., 2017; Tincoff & Jusczyk, 1999). At 9 months, after hearing a word paired with an object, infants looked longer at other objects in the same category than at those in a different category. They also expect different speakers of their native language to use object labels consistently, indicating that they grasp the shared nature of word meanings (Balaban & Waxman, 1997; Henderson & Woodward, 2012). Furthermore, by the end of the first year, babies know that the purpose of speech, even if unfamiliar, is to communicate (Martin, Onisha, & Vouloumanos, 2012). These understandings undoubtedly contribute to their motivation to use words in conventional ways.

First recognizable spoken words, around 1 year, build on the sensorimotor foundations Piaget described and on categories infants have formed. In a study tracking the first 10 words used by several hundred U.S. and Chinese (both Mandarin- and Cantonese-speaking) babies, important people (“Mama,” “Dada”), common objects (“ball,” “bread”), and sound effects (“woof-woof,” “vroom”) were uttered most often. Action words (“hit,” “grab,” “hug”) and social routines (“hi,” “bye”), though also appearing in all three groups, were more often produced by Chinese than U.S. babies, and the Chinese babies also named more important people—differences we will consider shortly (Tardif et al., 2008). Other investigations concur that earliest words usually include people, objects that move, foods, animals (in families with pets), familiar actions, outcomes of such actions (“hot,” “wet”), and social terms (Hart, 2004; Nelson, 1973). In their first 50 words, toddlers rarely name things that just sit there, like “table” or “vase.”

When toddlers first learn words, they sometimes apply them too narrowly, an error called underextension. At 16 months, Caitlin used “bear” only to refer to the worn and tattered teddy bear she carried nearly constantly. As vocabulary expands, a more common error is overextension—applying a word to a wider collection of objects and events than is appropriate. For example, Grace used “car” for buses, trains, trucks, and fire engines. Toddlers’ overextensions reflect their sensitivity to categories (MacWhinney, 2005). They apply a new word to a group of similar experiences: “car” to wheeled objects, “open” to opening a door, peeling fruit, and untying shoelaces. This suggests that children often overextend deliberately because they have difficulty recalling or have not acquired a suitable word. As vocabulary expands and pronunciation improves, overextensions gradually decline.

Overextensions illustrate another important feature of language development: the distinction between language production (the words and word combinations children use) and language comprehension (the language they understand). At all ages comprehension develops ahead of production. Think back to the distinction made earlier in this chapter between two types of memory: recognition and recall. Comprehension requires only that children recognize the meaning of a word. But for production, children must recall, or actively retrieve from their memories both the word and the concept for which it stands.

Still the two capacities are related. The speed and accuracy of toddlers’ comprehension of spoken language increase dramatically over the second year. And toddlers who are faster and more accurate in comprehension show more rapid growth in words understood and produced over the following year (Fernald & Marchman, 2012). Quick comprehension frees space in working memory for picking up new words and using them to communicate.

6.5.4 The Two-Word Utterance Phase

Young toddlers add to their spoken vocabularies at a rate of one to three words per week. Because gains in word production between 18 and 24 months are so impressive (one or two words per day), many researchers concluded that toddlers undergo a spurt in vocabulary—a transition from a slower to a faster learning phase. In actuality, most children show a steady increase in rate of producing new words that continues through the preschool years (Ganger & Brent, 2004). As a result, vocabulary growth seems to explode in the latter half of the second year.

How do toddlers build their vocabularies so quickly? In the second year, they improve in ability to categorize experience, recall words, and grasp others’ social cues to meaning, such as eye gaze, pointing, and handling objects (Golinkoff & Hirsh-Pasek, 2006; Liszkowski, Carpenter, & Tomasello, 2007). Furthermore, as toddlers’ experiences broaden, they have a wider range of interesting objects and events to label. For example, children approaching age 2 more often mention places to go (“park,” “store”). And as they construct a clearer self-image, they add more words that refer to themselves (“me,” “mine,” “Katy”) and to their own and others’ bodies and clothing (“eyes,” “mouth,” “jacket”) (Hart, 2004). In Chapter 9, we will consider the diverse strategies young children use to figure out word meanings.

Once toddlers produce 200 to 250 words, they start to combine two words: “Mommy shoe,” “go car,” “more cookie.” These two-word utterances are called telegraphic speech because, like a telegram, they focus on high-content words, omitting smaller, less important ones (“can,” “the,” “to”). Children the world over use them to express an impressive variety of meanings.

This 13-month-old has just begun to utter his first words (“car”). As his experiences broaden, he will label more objects and events with single words and then, between 18 ad 24 months, combine two words (“Go car” “Daddy car”) in telegraphic speech.

Two-word speech consists largely of simple formulas (“more + X,” “eat + X”), with different words inserted in the “X” position. Toddlers rarely make gross grammatical errors, such as saying “chair my” instead of “my chair.” But their word-order regularities are usually copies of adult word pairings, as when Carolyn remarked to Caitlin, “How about more sandwich?” or “Let’s see if you can eat the berries.” (Tomasello, 2003; Tomasello & Brandt, 2009). When 18- to 23-month-olds were taught noun and verb nonsense words (for example, “meek” for a doll and “gop” for a snapping action), they easily combined the new nouns with words they knew well (“more meek”). But they seldom formed word combinations with the new verbs (Tomasello, 2000; Tomasello et al., 1997). This suggests that they cannot yet flexibly form novel sentences that express subject–verb and verb–object relations, which are the foundation of grammar.

In sum, toddlers are absorbed in figuring out word meanings and using their limited vocabularies in whatever way possible to get their thoughts across. At first, they rely on “concrete pieces of language” they often hear, gradually generalizing from those pieces to word-order and other grammatical rules (Bannard, Lieven, & Tomasello, 2009; MacWhinney, 2015). As we will see in Chapter 9, they make steady progress over the preschool years.

6.5.5 Individual and Cultural Differences

Although children typically produce their first word around their first birthday, the range is large, from 8 to 18 months—variation due to a complex blend of genetic and environmental influences. Earlier we saw that Timmy’s spoken language was delayed, in part because of Vanessa’s tense, directive communication with him. But Timmy is also a boy, and research indicates that girls are slightly ahead of boys in early vocabulary growth (Frota et al., 2016; Van Hulle, Goldsmith, & Lemery, 2004). The most common explanation is girls’ faster rate of physical maturation, which is believed to promote earlier development of the left cerebral hemisphere.

Temperament matters, too. Highly sociable toddlers tend to be advanced in language progress (Pérez-Pereira et al., 2016). Shy toddlers often wait until they understand a great deal before trying to speak. Once they do speak, their vocabularies increase rapidly, although they remain slightly behind their agemates (Spere et al., 2004). Emotionally negative toddlers also acquire language more slowly because their high reactivity diverts them from processing linguistic information (Salley & Dixon, 2007).

Caregiver–child conversation—especially, the richness of adults’ vocabularies—also plays a strong role (Huttenlocher et al. 2010; Rowe, 2012). Commonly used words for objects appear early in toddlers’ speech, and the more often their caregivers use a particular noun, the sooner young children produce it (Goodman, Dale, & Li, 2008). Parents talk more to toddler-age girls than to boys, and they converse less often with shy than with sociable children (Leaper, Anderson, & Sanders, 1998; Mascaro et al., 2017; Patterson & Fisher, 2002).

Compared to their higher-SES agemates, children from low-SES homes usually have smaller vocabularies. By 18 to 24 months, they are slower at word comprehension and produce 30 percent fewer words (Fernald, Marchman & Weisleder, 2013). Limited parent–child conversation and book reading are major factors. Higher-SES parents typically interact more with their children, using a richer vocabulary, than do low-SES parents (Golinkoff et al., 2019; Hoff, 2006; Ramírez-Esparza, García-Sierra, & Kuhl, 2014). And on average, a middle-SES child is read to for 1,000 hours between 1 and 5 years, a low-SES child for only 25 hours (Neuman, 2003). Rate of early vocabulary growth is a strong predictor of low-SES children’s vocabulary size at kindergarten entry, which forecasts their later literacy skills and academic success (Rowe, Raudenbush, & Goldin-Meadow, 2012). Higher-SES toddlers who lag behind their agemates in word learning have more opportunities to catch up in early childhood.

Young children have distinct styles of early language learning. The vocabularies of Caitlin and Grace, like most toddlers, consisted mainly of words that refer to objects. A smaller number of toddlers produce many more social formulas and pronouns (“thank you,” “done,” “I want it”) (Bates et al., 1994). The vocabularies of object-naming toddlers grow faster because all languages contain many more object labels than social phrases.

Chinese toddlers use more words for actions and social routines than their English-speaking agemates. In Cantonese and Mandarin, verbs are emphasized. And perhaps because of cultural values, Chinese parents frequently use social formulas (“Thank you,” “It’s no trouble”), which their children acquire early.

Tim Graham/Getty Images

What accounts for a toddler’s language style? Rapidly developing children with a vocabulary of many object words often have an especially active interest in exploring their surroundings. They also eagerly imitate their parents’ frequent naming of objects, and their parents imitate back, which helps children remember new labels (Masur & Rodemaker, 1999). Toddlers who emphasize pronouns and social formulas tend to have parents who frequently use verbal routines that support social relationships (“How are you?” “It’s no trouble”).

The two language styles are also linked to culture. Object words (nouns) are particularly common in the vocabularies of English-speaking toddlers, whereas Chinese, Japanese, and Korean toddlers use more words for actions (verbs) and social routines. Mothers’ speech in each culture reflects this difference (Chan, Brandone, & Tardif, 2009; Choi & Gopnik, 1995; Fernald & Morikawa, 1993; Hao et al., 2015). American mothers frequently label objects when interacting with their babies. Asian mothers, perhaps because of a cultural emphasis on the importance of group membership, more often use words for actions and social routines. Also, in Cantonese, Mandarin, and Korean, nouns are often dropped from sentences when context leads them to be understood, leaving verbs to be produced more frequently (Gogate & Hollich, 2016). Consequently, action words are especially salient to toddlers acquiring these languages.

At what point should parents become concerned if their child talks very little or not at all? If a toddler’s language is greatly delayed when compared with the norms in Table 6.3 (page 231), then parents should consult the child’s doctor or a speech and language therapist. Late babbling, gesturing, and spoken words may be signs of slow language development that can be prevented with early intervention (Hsu & Iyer, 2016). Some toddlers who do not follow simple directions or who, after age 2, have difficulty putting their thoughts into words may suffer from a language disorder that requires immediate treatment.

Applying What We Know

Supporting Early Language Learning

Strategy

Consequence

Respond to coos and babbles with speech sounds and words.

Encourages experimentation with sounds that can later be blended into first words

Provides experience with the turn-taking pattern of human conversation

Establish joint attention and comment on what child sees.

Predicts earlier onset of preverbal gestures and words and faster vocabulary development

Play social games, such as pat-a-cake and peekaboo.

Provides experience with the turn-taking pattern of human conversation

Engage toddlers in joint make-believe play.

Promotes all aspects of conversational dialogue

Engage toddlers in frequent conversations.

Predicts faster early language development and academic success during the school years

Read to toddlers often, engaging them in dialogues about picture books.

Provides exposure to many aspects of language, including vocabulary, grammar, communication skills, and information about written symbols and story structures

6.5.6 Supporting Early Language Development

Consistent with the interactionist view, a rich social environment builds on young children’s natural readiness to speak their native tongue. For a summary of how caregivers can consciously support early language learning, see Applying What We Know above. Caregivers also do so unconsciously—through a special style of speech.

Adults in many cultures speak to young children in infant-directed speech (IDS), a form of communication made up of short sentences with high-pitched, exaggerated expression, clear pronunciation, distinct pauses between speech segments, clear gestures to support verbal meaning, and repetition of new words in a variety of contexts (“See the ball.” “The ball bounced!”) (Fernald et al., 1989; O’Neill et al., 2005). Deaf parents use a similar style of communication when signing to their deaf babies (Masataka, 1996). From birth on, infants prefer IDS over other kinds of adult talk, and by 5 months they are more emotionally responsive to it (Aslin, Jusczyk, & Pisoni, 1998). The features of IDS facilitate statistical learning of speech sounds and other speech units throughout the first year (Bosseler et al., 2016; Thiessen & Saffran, 2003).

IDS builds on several communicative strategies we have already considered: joint attention, turn-taking, and caregivers’ sensitivity to babies’ preverbal gestures. In this example, Carolyn uses IDS with 15-month-old Caitlin:

Caitlin: “Car.”

Carolyn: “Go in the car. Where’s your jacket?”

Caitlin: [Looks around; walks to the closet.] “Dackit!” [Points to her jacket.]

Carolyn: “There’s that jacket! [She helps Caitlin into the jacket.] On it goes! Let’s zip up. [Zips up the jacket.] Say bye-bye to Grace.”

Caitlin: “Bye-bye.” [Waves good-bye.] “G-ace!”

Carolyn: “Where’s your bear?”

Caitlin: [Looks around.]

Carolyn: [Pointing.] “By the sofa.” [Caitlin gets the bear.]

Notice how Carolyn kept her utterance length brief, just ahead of Caitlin’s, creating a sensitive match between language stimulation and Caitlin’s current capacities. Parents constantly fine-tune the length and content of their utterances in IDS to fit infants’ and toddlers’ needs—adjustments that promote vocabulary development in the second year, in monolingual and bilingual babies alike (Ma, Golinkoff, et al., 2011; Ramírez-Esparza, Kuhl, & García-Sierra, 2017; Rowe, 2008). (We will take up development of bilingualism in Chapter 12.)

As we saw earlier, caregiver–child conversation strongly predicts language development and later academic success. It provides many examples of speech adjusted to the child’s current level and a sympathetic environment in which children can try out new skills. Dialogues about picture books are particularly effective. They expose children to great breadth of language and literacy knowledge, from vocabulary, grammar, and communication skills to information about written symbols and story structures. From the end of the first year through early childhood, children who experience regular adult–child book reading are substantially ahead of their agemates in language skills (Karrass & Braungart-Rieker, 2005; Whitehurst & Lonigan, 1998).

A mother speaks to her baby in short, clearly pronounced sentences with high-pitched, exaggerated intonation. This form of communication, called infant-directed speech, eases language learning for infants and toddlers.

Research also suggests that one-on-one interaction with an adult is better suited to spurring early language development than speech directed to an infant or toddler in the presence of two or more adults (Ramírez-Esparza, Kuhl, & García-Sierra, 2017). The one-on-one context increases opportunities for sensitive, responsive interaction. Also, noisy background speech interferes with toddlers’ ability to acquire new words, though by age 2½, children are better language users and sufficiently experienced with noisy environments to learn from conversation despite distracting talk nearby (Dombroski & Newman, 2014; McMillan & Saffran, 2016).

Furthermore, live adult–toddler communication promotes language progress far more effectively than most media sources. After a month’s regular exposure to a commercial video for babies that labeled common household objects, 12- to 18-month-olds did not add any more words to their vocabulary than nonviewing controls. Rather, toddlers in a comparison group whose parents spent time teaching them the words in everyday activities learned best (DeLoache et al., 2010). Consistent with these findings, recall that a video chat format such as FaceTime, which enables an adult to interact responsively with a toddler, is an effective context for acquiring new words (see page 206).

Similarly, toddlers are able to learn new words from a touchscreen tablet only if the program allows them to participate in contingent interaction. In one study, 2½-year-olds acquired names of objects in a tablet presentation when their screen-touching enabled them to control the emergence of each object from a box and hear its spoken name, not when their touching merely advanced the screen and they watched as each object popped out of its box and was named (Kirkorian, Choi, & Pempek, 2016). Viewers younger than age 3 acquire little language from TV or video alone—even from programs specially designed for them (Krcmar, Grela, & Lin, 2007; Roseberry et al., 2009). Note how these findings illustrate the video deficit effect discussed earlier in this chapter.

Do social experiences that promote early language development remind you of those that strengthen cognitive development in general? IDS and parent–child conversation create a zone of proximal development in which children’s language expands. In contrast, adult behaviors that are unresponsive to children’s needs or impatient with their efforts to talk result in immature language skills (Cabrera, Shannon, & Tamis-LeMonda, 2007). In the next chapter, we will see that adult sensitivity supports infants’ and toddlers’ emotional and social development as well.

Ask Yourself

Connect ■ Cognition and language are interrelated. List examples of how cognition fosters language development. Next, list examples of how language fosters cognitive development.

Apply ■ Fran frequently corrects her 17-month-old son Jeremy’s attempts to talk and—fearing that he won’t use words—refuses to respond to his gestures. How might Fran be contributing to Jeremy’s slow language progress?

Reflect ■ Find an opportunity to interact with an infant or toddler. Did you use IDS? What features of your speech are likely to promote early language development, and why?

Summary

6.1 Piaget’s Cognitive-Developmental Theory (p. 197)

6.1a Explain how, in Piaget’s theory, schemes change over the course of development.

By acting on the environment, children move through four stages in which psychological structures, or schemes, achieve a better fit with external reality.

Schemes change in two ways: through adaptation, which consists of two complementary activities—assimilation and accommodation; and through organization, the internal rearrangement of schemes into a strongly interconnected cognitive system.

6.1b Describe major cognitive attainments of the sensorimotor stage.

In the sensorimotor stage, the circular reaction provides a means of adapting first schemes, and the newborn’s reflexes gradually transform into the more flexible action patterns of the older infant. Around 8 months, infants develop intentional, or goal-directed, behavior and begin to understand object permanence.

Twelve- to 18-month-olds engage in more deliberate, varied exploration and no longer make the A-not-B search error. Between 18 and 24 months, mental representation is evident in sudden solutions to sensorimotor problems, mastery of object-permanence problems involving invisible displacement, deferred imitation, and make-believe play.

6.1c Explain the implications of follow-up research on infant cognitive development for the accuracy of Piaget’s sensorimotor stage.

Many studies suggest that infants display a variety of understandings earlier than Piaget believed. Some awareness of object permanence, as revealed by the violation-of-expectation method and object-tracking research, may be evident in the first few months.

Furthermore, young infants display deferred imitation, an attainment that requires mental representation. Older infants and toddlers even imitate rationally, by inferring others’ intentions. Around the middle of the second year, toddlers begin forming mental representations of how to use an unfamiliar tool to secure a desired object.

The capacity for displaced reference—use of words to cue mental images of things not physically present—is a major advance in symbolic understanding that emerges around the first birthday. The use of language to modify mental representations improves from the end of the second into the preschool years. Awareness of the symbolic function of pictures emerges in the first year and strengthens in the second. Around 2½ years, the video deficit effect declines, and children grasp the symbolic meaning of video.

Today, researchers believe that newborns have more built-in equipment for making sense of their world than Piaget assumed, although they disagree on how much initial understanding infants have. According to the core knowledge perspective, infants are born with core domains of thought—including physical, psychological, linguistic, and numerical knowledge—that support rapid cognitive development.

Broad agreement exists that many cognitive changes of infancy are continuous rather than stagelike and that various aspects of cognition develop unevenly, rather than in an integrated fashion.

6.2 Information Processing (p. 210)

6.2a Describe the information-processing view of cognitive development and the general structure of the information-processing system.

Information-processing researchers generally assume that we hold and process information in three parts of the cognitive system: the sensory store; the short-term memory store; and the long-term memory store. The central executive joins with working memory—our “mental workspace”—to process information effectively. Well-learned automatic processes require no space in working memory.

Gains in executive function—including inhibition of impulses and irrelevant actions, flexible thinking, coordination of information in working memory, and planning—predict important cognitive and social outcomes.

6.2b Describe changes in attention, memory, and categorization over the first two years.

With age, infants gain attentional control and take information in more quickly. In the second year, attraction to novelty declines and sustained attention improves.

Short-term memory increases from 6 months on, and working memory emerges at the end of the first year. Operant conditioning and habituation research show that long-term retention of visual events increases greatly with age.

By the middle of the first year, infants can engage in recall as well as recognition memory.

A combination of factors—neurological changes, increasing reliance on verbal means for storing information, and firmer self-awareness—may account for the decline of infantile amnesia and the emergence of autobiographical memory.

Infants group stimuli into an expanding array of categories. In the second year, toddlers begin to categorize flexibly, switching their basis of object sorting, and their grasp of the animate–inanimate distinction expands. Babies’ exploration of objects, expanding knowledge of the world, and advancing language skills foster categorization.

6.2c Explain the strengths and limitations of the information-processing approach to early cognitive development.

Information-processing findings challenge Piaget’s view of infants as purely sensorimotor beings who cannot mentally represent experiences. But information processing has not yet provided a broad, comprehensive theory of children’s thinking.

6.3 The Social Context of Early Cognitive Development (p. 218)

6.3 Explain how Vygotsky’s concept of the zone of proximal development expands our understanding of early cognitive development.

Vygotsky believed that children master tasks within the zone of proximal development—ones just ahead of their current capacities—through the support and guidance of more skilled partners. As early as the first year, cultural variations in social experiences affect mental strategies.

6.4 Individual Differences in Early Mental Development (p. 219)

6.4a Describe the mental testing approach, the meaning of intelligence test scores, and the extent to which infant tests predict later performance.

The mental testing approach measures intellectual development in an effort to predict future performance. Scores are arrived at by computing an intelligence quotient (IQ), which compares an individual’s performance with that of a standardization sample of same-age individuals, whose performances form a normal distribution.

Infant tests consisting largely of perceptual and motor responses predict later intelligence poorly. As a result, scores on infant tests are called developmental quotients (DQs), rather than IQs. Speed of habituation and recovery to novel visual stimuli is among the best available predictors of future IQ.

6.4b Discuss environmental influences on early mental development, including home, child care, and early intervention for at-risk infants and toddlers.

Research with the Home Observation for Measurement of the Environment (HOME) shows that an organized, stimulating home environment and parental affection, involvement, and encouragement repeatedly predict better language and IQ scores. Although the HOME–IQ relationship is partly due to heredity, family living conditions also affect mental test scores.

Quality of infant and toddler child care influences cognitive, language, academic, and social skills. Standards for developmentally appropriate practice specify program characteristics that meet young children’s developmental needs.

Intensive intervention beginning in infancy and extending through early childhood can help prevent the gradual declines in intelligence and the poor academic performance evident in many poverty-stricken children.

6.5 Language Development (p. 227)

6.5a Describe theories of language development, and indicate the emphasis each places on innate abilities and environmental influences.

According to Chomsky’s nativist theory, language is a uniquely human capacity made possible by a language acquisition device (LAD), an innate system containing a universal grammar underlying all languages.

Evidence for specialized language areas in the brain and for a sensitive period of language development support Chomsky’s theory. Challenges include the inability to specify the rules of universal grammar and evidence that children’s language development involves more experimentation and learning than Chomsky assumed.

Interactionist theories suggest that language development results from interactions between inner capacities and environmental influences. Some interactionists apply the information-processing perspective to language development. Others emphasize the importance of children’s social skills and language experiences.

6.5b Describe major language milestones in the first two years, individual and cultural differences, and ways adults can support early language development.

Infants begin cooing at 2 months and babbling around 6 months. Around 10 to 11 months, their skill at establishing joint attention improves, and at the end of the first year they use preverbal gestures.

Around 12 months, toddlers say their first word. As they learn new words, they make errors of underextension and overextension. At all ages, comprehension develops ahead of production. Vocabulary typically increases at a steady rate, and once it reaches about 200 to 250 words, toddlers begin producing two-word utterances called telegraphic speech.

Girls acquire early vocabulary faster than boys, and both shy and emotionally negative toddlers acquire language more slowly than others. Low-SES children, who receive less verbal stimulation than higher-SES children, have smaller vocabularies—a strong predictor of later weak literacy skills and academic performance.

The vocabularies of most toddlers consist mainly of words that refer to objects. A smaller number produce more social phrases, and their vocabularies grow more slowly. These differences are linked to toddlers’ individual attributes and to culture.

Adults in many cultures speak to babies in infant-directed speech (IDS), a simplified form of communication that is well-suited to their learning needs. Live interaction with a responsive adult is better suited to early spurring language progress than are media sources, which are effective only if they permit contingent interaction.

IMPORTANT TERMS AND CONCEPTS

accommodation (p. 198)

adaptation (p. 198)

A-not-B search error (p. 200)

assimilation (p. 198)

autobiographical memory (p. 216)

automatic processes (p. 212)

babbling (p. 231)

central executive (p. 212)

circular reaction (p. 199)

cooing (p. 231)

core knowledge perspective (p. 207)

deferred imitation (p. 201)

developmentally appropriate practice (p. 224)

developmental quotient (DQ) (p. 222)

displaced reference (p. 205)

executive function (p. 212)

Home Observation for Measurement of the Environment (HOME) (p. 222)

infant-directed speech (IDS) (p. 236)

infantile amnesia (p. 216)

intelligence quotient (IQ) (p. 221)

intentional, or goal-directed, behavior (p. 200)

joint attention (p. 232)

language acquisition device (LAD) (p. 227)

long-term memory store (p. 212)

make-believe play (p. 201)

mental representation (p. 201)

normal distribution (p. 221)

object permanence (p. 200)

organization (p. 198)

overextension (p. 233)

recall (p. 214)

recognition (p. 214)

scheme (p. 198)

sensorimotor stage (p. 197)

sensory store (p. 211)

short-term memory store (p. 211)

standardization (p. 221)

telegraphic speech (p. 234)

underextension (p. 233)

video deficit effect (p. 206)

violation-of-expectation method (p. 201)

working memory (p. 211)

zone of proximal development (p. 218)