National Academies Press: OpenBook

Eager to Learn: Educating Our Preschoolers (2001)

Chapter: 2	What Does the Science of Learning Contribute to Early Childhood Pedagogy?

« Previous: 1	Introduction
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

2
What Does the Science of Learning Contribute to Early Childhood Pedagogy?

AS RECENTLY AS 50 YEARS AGO, it was widely believed that the major tasks for children during the preschool years were those of socialization: separating from home, learning how to interact with peers and unfamiliar adults, and experiencing new materials in a novel environment. Today we recognize the first five years as a time of enormous growth of linguistic, conceptual, and social competence. Right from birth, healthy infants use their limited response abilities to explore—and even control—their environments. They gather information about faces, about sounds and language, about objects and events (Morton and Johnson, 1991; Spelke, 1990; Kuhl et al., 1992; Mehler et al., 1986; Gopnik and Meltzoff, 1992).

How do we know that infants are active participants in their learning when their abilities and competence are so clearly limited? Careful observation reveals that infants indicate attentiveness through gestures such as shifting their gaze, turning their head slightly, actively kicking their legs or waving their arms, and engaging in nonnutritive sucking. These indicators of selective attention have allowed researchers to study the capacity of babies to participate actively in learning about the world around them.

A study of 4-month-old infants, for example, found that they engaged in vigorous nonnutritive sucking when first introduced to the phoneme “ba.” With repeated exposure, the infants lose

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

interest (the sucking wanes). But when presented with the new phoneme “pa,” sucking again becomes vigorous, signaling recognition of the change (Eimas et al., 1971). Similar research has indicated attentiveness in the form of shifting gaze in infants as young as 5 months in response to changes in number (Canfield and Smith, 1996). And bodily actions such as kicking and arm waving have, in controlled experiments, indicated the object recognition capacity of infants (Rovee-Collier, 1989).

As they have crafted procedures suited for toddlers and preschool-age children, researchers have documented early cases of abstract reasoning and self-motivated efforts to learn (National Research Council, 1999; Goswami, 1995). In a study by Karmiloff-Smith and Inhelder (1974–1975), preschool children were offered repeated opportunities (over several sessions) to balance each one of a set of blocks on top of another block. Some of the blocks had concealed weights and therefore did not balance at their geometric centers. Initially children succeeded at balancing each block, no matter what kind it was, by using a combination of trial and error and brute force. When a trick block fell, a child moved it around while pushing down on it until balance was achieved. After repeated opportunities to play with the blocks, children started to behave as if they were systematically applying a “blocks balance at their midpoint” hypothesis. As a result, they now started to make errors with the trick blocks. These they placed aside, saying things like “don’t work.”

Of special interest is the fact that there came a time when children changed their strategy again, in a seeming effort to find an all-inclusive solution. On their own they came to realize that they would have to use a third block as a counterweight for blocks that they could feel would not balance at their geometric center. Therefore, they were once again able to balance all the blocks. It is important to highlight the fact that these children gave up the trial-and-error solution that worked in favor of a more systematic one. Had they not done so, they would not have generated the negative data that eventually encouraged them to find a yet more advanced solution.

This view of the child as having ideas or theories about how things work, and as actively engaged in the construction of knowledge stands in stark contrast to earlier views of develop-

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

ment. Advances in cognitive abilities do not simply unfold with age; nor is the child a passive receptacle for the knowledge delivered by others. Rather, current understandings suggest that cognitive development takes place in the context of the child’s interactions with others and with the environment—interactions in which the child is a very active participant. The implications for learning opportunities and for early childhood pedagogy are substantial. The child’s current understandings must be engaged and built on; knowledge cannot simply be provided for the child. When learning is the product of the child’s guided construction rather than the teacher’s transmission and the child’s absorption, what is learned becomes very individualized. And teaching becomes a two-way relationship in which the teacher’s understanding of the child is at least as important as the child’s understanding the teacher.

Current conceptions of early childhood development and pedagogy are built on a century of research. A review of central ideas from that research literature can inform the understanding of current pedagogical ideas and beliefs.

THEORIES OF COGNITIVE DEVELOPMENT

Philosophers such as Renee Descartes, John Locke, Immanuel Kant, and Karl Marx have heavily influenced developmental psychology (for a history of these influences, see Cairns, 1983). The powerful influences of these different philosophical traditions, combined with the complex nature of human development, help explain the diversity of theories germane to early childhood pedagogy.

Over the course of this century, preschool pedagogy in the United States has tended to focus on one or two grand theories for a period, then move on to another theoretical perspective, and so on. For example, at mid-century there were many who embraced the ideas of “behavioral objectives” and positive reinforcement. Others focused on the idea that young children’s affective-social systems should be the focus of attention, a clear influence of Freud.

By the 1970s, Piagetian stage theory helped educators structure exploratory learning opportunities, especially as regards one

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

involving the ability to use symbols and reason about quantities, classifications, and the perspective of others. From Piaget’s point of view, the main accomplishments of the preschool (or “pre-operational”) period involve the development of symbolic abilities, language, imitation, symbolic play, and drawing. There is no doubt that there is a great deal of learning in these symbolic abilities. Still, for Piaget, the young child’s thoughts take place in the here and now and on the perceptual level. Preschool children therefore do not have the conceptual structures that enable hierarchical classification skills or sophisticated quantitative reasoning.

This side of Piaget’s theory of preschool thought is shared by two other prominent child development thinkers, Jerome Bruner and Lev Vygotsky. Despite their differences, all converge on the premise that preschool children’s conceptual abilities are perception-bound. The influence on preschool pedagogy of this confluence was straightforward. It was appropriate to provide children with concrete materials to explore and categorize. However, it was developmentally inappropriate to include learning opportunities about abstract categories, measurement, and advanced arithmetic, for doing so was asking children to deal with tasks for which they lacked the conceptual capabilities.

This assumption continues to be prevalent in the world of practice, especially as regards some interpretations of the notions of “readiness” and what is “developmentally appropriate.” However, the very definitions of these terms are being redefined as new research on the abilities and potential competencies of young children emerges. It has now been shown, for example, that whether or not young children use abstract classification schemes is very dependent on what they know about the materials to be sorted.

Beyond Piaget

The kinds of data that stage theorists of cognitive development obtained are reliable across a wide range of conditions and domains. However, those data coexist with evidence that, when they have accumulated substantial knowledge, children can perform in a particular domain at a level of development beyond

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

what is expected given the child’s age and development in other domains.

When children know a great deal about something—so much so that we can say they have achieved a principled organization of it—they can deploy hierarchical classification structures. A compelling example comes from studies by Gobbo and Chi (1986) of preschool dinosaur experts. These children were able to sort dinosaurs on the basis of multiple criteria (whether they were land-living or not, meat-eating or not, and so on), demonstrating classification ability that was beyond expectation. Since children who know much less about dinosaurs generate data that resemble the results from the traditional classification tasks, it appears that the key variable here is knowledge, not the presence or absence of classification abilities per se (see Carey, 1985).

The effect of knowledge on competence is demonstrated in two cognitive tasks that young children often fail: a perspective-taking task and a conservation of number task. On the perspective-taking task, young children are found to lack the ability to take a perspective other than their own. However, as shown by Borke (1975), if the task is presented in a familiar context, in this case as characters from “Sesame Street,” they are more likely to be able to take a perspective other than their own. On the conservation of number task, young children will mistake a longer line of items as having “more” even though a longer line has the same number of items with bigger spaces between them. This is the case even when the two lines of items are initially the same length and it is pointed out that they have the same number of items. However, Donaldson (1978) found that if a “Puppet—Naughty Teddy” messed up two lines with equal numbers, making one line longer, children were less likely to indicate that the longer line had more.

The tension between the view of cognitive development as taking place systemically in response to endogenous, often biological change, and the view that it occurs in specific domains in response to exogenous influences has fueled much research that is still ongoing. Researchers from different theoretical perspectives frame their questions differently, and their inquiry often uses different research techniques (Case, 1991). Compelling findings from both lines of inquiry call for a more integrated understand-

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

ing of cognitive development in which both exogenous and endogenous factors are at play, and in which some systemic limits are recognized which, while providing a ceiling on development, allow for wide variation below that ceiling in response to exogenous influences. Indeed, numerous theories do incorporate the idea of structured cognitive development, but allow for cognitive structures to be assembled independently rather than systemically, with environmental context and culture playing a central role in the development of the individual’s cognitive landscape (Case, 1985; Fischer, 1980; Halford, 1982; Halford and Leitch, 1988; Pascual-Leone, 1988a, 1988b).

Cognition in Context

Closely tied to the understanding of the influence of knowledge acquisition on cognitive development is the research on “cognition in context.” Although Piaget made it clear that the development of cognitive structure depends on the opportunity for children to interact with supporting environments, he did not focus on how to characterize relevant inputs for epigenesis. The late 1980s witnessed an explosion of work on the social and cultural contexts of cognitive development (e.g., Bronfenbrenner and Ceci, 1994; Rogoff, 1990; Sternberg, 1985; Fischer and Knight, 1990). For example, drawing on a train metaphor, Bronfenbrenner and Ceci proposed that “the basic psychological and biological processes are the ‘engines’ that drive intellectual development and context provides the fuel and steering wheel to determine how far and in what direction it goes” (1994:404).

Social-cultural contexts affect cognitive processing in multiple ways, and different lines of research focus on different aspects of context. Sociocultural theory emphasizes that cognitive activity and development occur in social situations. Children engage in problem-solving activities in collaboration with an adult who structures and models ways to solve the problem. This is referred to as coconstruction. Vygotsky (1978) and Rogoff (1990) best articulate the theory by which children’s problem solving is conducted under the guidance and supervision of adults, who structure the interaction to guide children through tasks that are just beyond their capacities. The window of opportunity for the adult

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

to enter into the child’s experience and enable him to move toward developing higher mental processes is called the zone of proximal development (ZPD). “The lower level of the ZPD is defined by the child’s independent performance and its upper level is defined by the most a child can do with assistance” (Bodrova, 1997:20). As long as the child’s knowledge remains where improvement is still possible with adult assistance, the child is said to be within the ZPD. With adult help, the child may advance toward independent and autonomous thinking.

One important strategy that the adult employs is called scaffolding, in which questions or discussion are used to help the child advance incrementally to a higher level of thinking. In a way, this is analogous to Piaget’s notion of the child moving from stage to stage. The difference is that in Vygotsky’s approach the movement upward is possible with appropriate guidance; it is not as dependent on the unfolding of an endogenous developmental process. Vygotsky thus gives instruction a more central role in development than does Piaget.

Another critical concept in the Vygotskyan perspective is that of mental tools. For a child to acquire these tools en route to higher-order mental function like abstract reasoning, the child has to be helped by knowing individuals, teachers, or parents. This can occur in school or at home. Mental tools come in various forms including the development of strategies to remember and to solve problems (such as trial-and-error and counting-on strategies), developing analogies, or reviewing related information or ideas. Their common characteristic is that they help the child restructure his thinking. Gelman, in discussing the teaching of arithmetic to young children, emphasizes the importance of recognizing that even the young child develops some knowledge and concepts of mathematics that can be built on (Gelman, 2000). The use of questions and demonstrations can help draw out existing knowledge and build on it, contributing to a restructuring of the child’s understanding.

The last 30 years have witnessed a considerable growth in evidence of strategic and metacognitive competence at an early age, especially when children are asked about topics or problems they understand (Brown and DeLoache, 1978; DeLoache et al., 1998). Children can think about their own thinking and the think-

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

ing and intentions of others. Recent research on “theories of mind” suggest that not only can children intentionally learn, but they can develop theories of what it means to learn and to understand that affect how they function in situations that require effortful learning (Bereiter and Scardamalia, 1989). The more they understand what the learning process requires—that it is not simply a matter of knowing or not knowing, of performing well or of failing to perform—the more directed they will be toward the learning goal (Dweck, 1989; Dweck and Elliott, 1983; Dweck and Leggett, 1988). Researchers have documented cases of preschool children using strategies to remember (Wellman et al., 1975; DeLoache et al., 1985), to count (Siegler, 1988) and to solve problems (National Research Council, 1999).

An older and large body of research, less explicitly linked to sociocultural theory but also focusing on the role of the adult, suggests an optimal adult-child interaction for children’s cognitive and language development. It is one that fosters reciprocity in which adults make overtures to children that are in tune with their current attentional focus, building on the children’s activities, prior knowledge, and skill level (Akhtar et al., 1991; Belsky et al., 1980; Bloom et al., 1976; Bornstein and Tamis-LeMonda, 1989; Bruner and Olson, 1977; Gralinski and Kopp, 1993; Kuczynski, 1984; Landry et al., 1997; Rocissano and Yatchmink, 1984; Parpal and Maccoby, 1985; Schaffer and Crook, 1980; Tomasello and Farrar, 1986a, 1986b). This reciprocal and responsive adult-child interaction is related to better cognitive and language outcomes (Bornstein and Tamis-LeMonda, 1989; Crockenberg and Litman, 1990; Maccoby and Martin, 1983; Power and Chapieski, 1986; Olson et al., 1984; Tomasello and Farrar, 1986a, 1986b; Weiss et al., 1992). This literature is based primarily on maternal behavior. Its relevance to early education and care is expanded in Chapter 5 and also in Chapter 7, when we discuss professional development.

In a similar vein, Kurt Fischer and his colleagues argue that competence is “an emergent characteristic of a person-in-context, not a person alone” (Fischer et al., 1993). They conducted many research studies on children between 3 and 18 years of age to measure the influence of contextual support on competence. Children were asked to carry out tasks (such as producing mean and

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

nice stories, sorting blocks into boxes) in contexts ranging from no support (spontaneous performance) to high support (in the form of direct modeling of the performance task).

Performances were then rated on a developmental scale. A consistent, substantial difference in performance was found between the “functional level” in the low support context, and the “optimal level” in the high support context. In one such study conducted with 7-year-olds, the children were asked to produce stories about mean and nice, and their spontaneous responses were scored at or below stage 3 on the developmental scale, whereas their independently executed response after modeling was at or below stage 6, suggesting a potentially powerful influence of context (Fischer et al., 1993). Fischer refers to the gap as the child’s “developmental range,” a concept that differs somewhat from Vygotsky’s zone of proximal development. The adult does not actually help the child do the more difficult aspects of the task. Rather, the child observes through exposure or modeling more developmentally sophisticated approaches to a task, which changes his or her own performance.

Much research has also emphasized the role of cultural context on cognition. Culture is seen as providing the content—the objects and ideas—of thinking. For example, in a study of schooled and unschooled children from an agricultural community outside the United States and schoolchildren from the United States, Lantz (1979) found that a simple change from thinking about an unfamiliar set of objects to a familiar set of objects dramatically affected children’s performance. Both the rural unschooled and schooled children outperformed children from the United States when the task involved seeds and grains. However, children from the United States did much better than the other children when the same task was presented using a set of colored disks. Thus, although the children were asked to do the same thing with the seeds and grains as with the colored disks, the content of the task affected their performance.

Cultural context also determines the tools people use to support thinking. Brazilian children who work as street vendors mentally complete mathematical computations in their normal business transactions every day. However, when these children were given paper-and-pencil versions of the same problems, their

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

performance declined significantly. Schliemann et al. (1998) suggested that oral mathematics and written mathematics relied on different symbolic representations of the information, which in turn lent themselves to different strategies for solving the problems. The children had become experts in solving problems according to one strategy, but not the other. Similarly, Scribner (1984, 1985) posited that the tools and features of everyday contexts become part of people’s thought processes. In her studies of problem solving in work contexts, she observed the ways in which individuals developed problem-solving strategies that capitalized on features of their work environments.

Functional familiarity also affects thinking. An expert-novice study of recall for the configuration of chess pieces by Chase and Simon (1973) demonstrated the role of functional familiarity in a memory task. When the chess pieces were arrayed in meaningful chess patterns, i.e., in terms of the game’s structure, expert chess players well outperformed the novices in their ability to remember where the pieces were on the board when it was no longer in view. However, when the chess pieces were placed in random positions on the board, the experts did not do any better than the novices—even though the task was ostensibly the same task. Chi (1978) replicated these results comparing expert child chess players with novice adult chess players. Just as an array of chess pieces can represent a strategy or pattern that is recognizable to those familiar with the game of chess but unrecognizable to chess novices, objects and ideas will take on different meaning to individuals that reflect the function or importance of those ideas in an individual’s culture. And in doing so, culture influences their thought processes.

Implications

The more global limitations on developmental stages suggested by Piagetian and neo-Piagetian theorists, confirmed in many empirical studies, give meaning to the notion of “developmentally appropriate” preschool programs. There do appear to be limits on the capacities of children in a developmental period that represent a ceiling beyond which very few can go. At the same time, however, there is much research to suggest that chil-

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

dren are capable of learning a great deal when they are in environments that support their development. The responsiveness of children’s development to exogenous opportunities to learn, and to interactions that support their learning, suggests the potentially important role that preschool programs can play in providing a context and a set of relationships that can promote development.

What are the characteristics of context in which a child’s development is well supported? There is a growing body of research that suggests that cognitive stimulation—exposure to ideas, information, and stories—is one element of a picture in which the social and emotional context of learning is prominently featured. Piaget wrote of the link between the emotional and the cognitive quite eloquently: “There is a constant parallel between the affective and intellectual life throughout childhood and adolescence. This statement will seem surprising only if one attempts to dichotomize the life of the mind into emotions and thoughts. But nothing could be more false or superficial. In reality, the element to which we must constantly turn in the analysis of mental life is ‘behavior’…. All behavior presupposes instruments and a technique: movements and intelligence. But all behavior also implies motives and final values (goals): the sentiments. Thus affectivity and intelligence are indissociable and constitute the two complementary aspects of all human behavior” (Piaget, 1967:15).

Emotion and behavior are, like cognition, located not just in the individual, but in the individual in context. Emotional security allows for more effective exploitation of learning opportunities. Moreover, learning requires self-regulation. Therefore behavioral issues, and the social and emotional environment of preschool classrooms that affect behavior, are crucial to effective learning.

SOCIAL AND EMOTIONAL CONTEXT: THE IMPORTANCE OF RELATIONSHIPS

As is the case with cognitive development, the social and emotional development and behavior of children has been the subject of a plethora of theories in the past century. In earlier years the theories generally attributed children’s behavior to their parents’

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

childrearing, though the specifics of the explanations varied. However, there has been an evolution in complexity in the models used by developmental researchers since the 1940s (e.g., Sameroff, 1994). A relatively consistent position can be seen across most contemporary approaches and models in accepting the bidirectionality (mutuality) of influences between a child and parents, teachers, siblings, or peers, and for an expanded understanding of the role of the environment.

Tronick (1989) clearly indicates the centrality of the role of emotional communication from the earliest moments in a child’s development. The effectiveness of emotional communication between infants and caregivers contributes to a child’s eventual well-being. Tronick argues that infants’ emotional communication is more organized than heretofore considered, that an infant appreciates how caretakers respond to him, which allows for a mutual regulation of their interactions. When the interactions are positive, when the two are synchronized and mutually supporting, development is enhanced. And negative communication yields negative consequences.

Tronick offers a prototypical example where the infant is reaching for an object but cannot retrieve it, so the infant indicates distress. After two tries the adult moves the object closer and the child retrieves the object and smiles. It is at these types of intersections where the adult responds positively to the child’s intention from which healthy emotional development will eventuate. Therefore, rather than consider cognition and emotion as distinct domains, the implication of Tronick’s study and others like it is that cognition and emotion are part of the whole.

More recent models that assign importance to interactions between the child and adults other than the mother are applicable to the behavior of children in preschool settings. The transactional model of Sameroff and Chandler (Sameroff, 1975), for example, is equally appropriate for families and classrooms because it takes into account whatever environment the child is in. In applying this model the child’s behavior is viewed in the context of the classroom, including physical arrangement, the curriculum materials, the schedule or ordering of events, the classroom rules, and ongoing processes, as well as the teacher and peers. The child brings his or her own characteristics, clearly in-

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

fluenced by relationships in the home environment, as well as the family’s culture, values, and beliefs.

Children and Adults

There is evidence that the transactional processes manifested by children and their parents in the home are seen in child-child and child-teacher relationships in school settings. Relevant work on these occurrences has been conducted by Patterson and his colleagues on the origins of antisocial behavior in childhood (Patterson, 1986).

John Bowlby’s attachment theory (1969) has been expanded in the past decade (Howes 1999; Pianta, 1994) to encompass the notion of attachment networks. This contrasts with its earlier emphasis on the primacy of the child-mother attachment. In these more recent formulations, teachers in early childhood education programs are considered attachment figures because they provide physical and emotional care, and they are consistent and predictable in children’s lives. From the children’s perspective, these adults provide comfort, a secure base, and serve to organize the children’s behaviors in the setting.

Research that examines behavior in contexts outside the home has produced a large body of evidence on the validity of assessing relationships between children and teachers, identifying and examining antecedents of different qualities of the relationships, and examining the concurrent and long-term correlates of relationship qualities and children’s social competence. The findings of these studies suggest that the quality of a child-teacher attachment can be reliably and validly assessed, that similar processes are implicated in the formation of attachments of different qualities with alternative caregivers and with the child’s mother, and that attachment security with the alternative caregiver predicts social competence in the long and the short term. Children with more positive teacher-child relationships appear more able to exploit the learning opportunities available in classrooms (Howes and Smith, 1995), construct positive peer relationships (Howes et al., 1994), and adjust to the demands of formal schooling (Birch and Ladd, 1997; Pianta and Steinberg, 1992; Lynch and Cicchetti, 1992). An important caveat to this research is that the way in

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

which secure attachment relationships are demonstrated may differ across cultural groups (e.g., Harwood, 1992).

The quality of children’s early relationships with their teachers in child care is emerging as an important predictor of children’s social relations with peers (Howes et al., 1994; Howes and Tonyan, in press), their behavior problems (Howes et al., 1998), and school achievement as older children (Howes et al., in press). Perhaps most important for the work of this committee, if children feel emotionally secure with the teacher, they can use her as a secure base and a resource for exploring the learning opportunities of the classroom (Birch and Ladd, 1997; Howes et al., in press; Howes and Smith, 1995; Lynch and Cicchetti, 1992; Pianta and Steinberg, 1992).

More recent theoretical work from this perspective has included the social-emotional climate of the classroom as well as the individual relationship between the child and the teacher (Boyce et al., and the MacArthur Network on Psychopathology and Development, 1998). According to this perspective, the individual child-teacher relationship and teacher perceptions of individual children’s behavior problems are constructed in the context of classroom climates. The classroom social-emotional climate is defined as consisting of the level of aggression and other behavior problems in the group of children, the nature of the child-teacher relationships, and the frequency and complexity of play with peers. Using this notion of classroom climate, classrooms can be described on a continuum from positive, prosocial environments characterized by close adult-child relationships, intricate pretend play scenarios, and little disruptive behavior to angry, hostile environments characterized by conflictual child-teacher-relationships, angry disruptive children, and little constructive peer play or collaborative learning.

An alternative approach to early childhood pedagogy, also derived from attachment theory, emphasizes the socialization function of the adult. If a teacher constructs positive and secure attachment relationships with children, in part by responding positively and consistently to children’s appropriate behavior, so that there is a predominance of what Kochanska (1997) calls mutually reciprocal relationships, then classroom management becomes an issue of constructing, maintaining, and sustaining har-

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

monious relationships rather than managing and avoiding potential conflict. There is very little empirical data on this topic, however.1

Early researchers examining links in infants between attachment security and self-regulation found that infants who were classified as secure were more compliant and showed less frustration and aggression as toddlers (Matas et al., 1978; Londerville and Main, 1981). More recently, Kochanska (1997) has used Maccoby’s (1984) construct of a mutually reciprocal relationship to examine the processes linking secure attachment and self-regulation. If toddlers trust their caregiver, then they are more willing and eager to be socialized. Furthermore, the experience of a mutually reciprocal relationship means that both partners, the toddler and the adult, feel invested in and responsible for each other’s welfare; each feels concern for and acts responsively to the other’s needs, and, at the same time, each comes to expect the other to be responsive to one’s needs and to be concerned about one’s welfare (Kochanska, 1997:94).

This kind of relationship is very different from the adversarial relationship sometimes implied in the socialization literature. In terms of behavioral interaction, a mutual responsive relationship means that there is a diminished need for adult use of power or coercion strategies. Instead, because the child is eager to cooperate with the adult, socialization strategies do not need to be harsh or restrictive. The existence of a mutually reciprocal relationship means that children’s socialization can extend beyond task compliance toward building a foundation for rules of conduct and morality.

There are implications in these associations between attachment security and self-regulation for classroom management in early childhood programs. If teachers can construct secure attachments with the children in their care, then they may have less need for discipline strategies, such as time out or behavior conse-

1  

All the literature available was conducted with regard to infant-mother attachment. Since child-teacher attachments appear to function similarly to infant-mother attachments (Howes, 1999), a similar pattern of results could be assumed for child-teacher attachment relationships.

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

quences that are outside a cooperative relationship. To develop that sort of trust between caregiver and child, it is necessary to provide positive consequences, a point that has been stressed by the behavioral approaches, as has the need for setting expectations and giving clear directions. This literature does bring with it a wealth of empirical support that bolsters the notion that teachers who have a relatively sophisticated grasp of the attachment and behavioral literature, can promote the kind of attachment that helps children develop self-regulation.

In sum, one of the most consistent findings in the early childhood literature is that an emotionally warm and positive approach in learning situations leads to constructive behavior in children. The teacher’s tone of voice and the use of positive consequences to encourage desired behavior, just to mention two examples, are key to teacher strategies advocated by virtually all preschool programs.

Importance of Peers

Attention to peer relations dates back to the 1930s and 1940s when researchers studied children’s friendship patterns; interest reemerged again in the 1970s, with major contributions occurring during the past two decades (e.g., Hartup, 1983). Children’s peer relations are seen as more complex than was initially conceptualized, with areas such as social group status, mutual friendships, and peer networks seen as separate aspects of peer relations (Bierman and Welsh, 1997). Aspects of children’s development such as communication skills, helping behavior, play, and conflict resolution, are important dimensions of peer relations (Greenfield and Suzuki, 1998). Parent-child interactions and family experiences influence peer relations (e.g., Parke and Ladd, 1992) as well as the child’s culture and beliefs (Greenfield and Suzuki, 1998; Bierman and Welsh, 1997). Another major variable influencing peer relations is a child’s social competence, that is, the child’s ability to elicit positive responses from others (Dodge, 1985).

One of the most compelling findings related to peer relations is that positive peer relations have a significant role in supporting

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

a child’s social and emotional development (Parker et al., 1995). A number of studies have documented relationships between poor peer relationships and children’s later school difficulties and mental health problems (e.g., Parker et al., 1995). From a longitudinal study of kindergarten children (Wasik et al., 1993; Wasik, 1997), results showed that children’s peer status, as rated by their peers within the first three months of kindergarten, was highly predictive of their social and academic performance in third grade. Other researchers have documented the predictive value of children’s social status in the elementary grades for later school success and mental health adjustment in adolescence (Lynch and Cicchetti, 1997).

Collectively these findings and those of many other researchers during the past two decades make it clear that children’s social interactions and peer relations are critical considerations when young children come together in education and care settings. Teachers and other staff need to be careful observers and knowledgeable of ways to facilitate positive peer relations.

DEVELOPMENT OF THE BRAIN

The proliferation of research on the brain that has accompanied advances in brain imaging technology has provided a physiological description of the mind’s organ that in some respects complements the understanding that is emerging from research in developmental and cognitive psychology. The brain undergoes enormous changes as a child grows and acquires skill in dealing with the environment. We first consider some findings in neurobiology related to the role of experience in shaping brain circuits. Then we examine findings based on neuroimaging of the anatomy and circuitry involved in high-level skills.

It is important at the beginning of this discussion to caution against thinking that brain research is directly applicable to instruction and pedagogy. There are many popular accounts and heavily promoted learning programs that make that leap, but so far, there is no evidence of the effectiveness of particular educational programs, methods, or techniques on brain development (see National Research Council, 1999: Chapter 5; Bruer, 1997).

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

Genetics and Environment

Recent research in developmental biology has already altered the basis of the traditional nature-nurture debate. One is born with a given set of genes; however, the expression of those genes in the characteristics of the individual is not fixed; gene expression depends on the environment. Thus, the interaction between nature and nurture operates at every level, including the molecular one. A view of genetic expression as quintessentially dependent on environmental interactions allows for acceptance of genetic influences on the part of the behavioral sciences without the need to forfeit the important role played by the social environment. Indeed, there is every reason to expect some social environments to influence biological variables.

While much of the nervous system develops prior to birth, for primates and particularly humans a long period of postnatal development is needed to complete the basic formation of the brain. Two basic biological principles dominate current understanding of how nervous systems are put together. The first, neuronal specificity, posits that neuronal connections are specified with great precision during their development (Sperry et al., 2000). This principle has been used to support the selectionist view, according to which the role of experience is limited to selecting from a rich innate repertoire of connections. This view stresses the overproduction of synapses in early life and their pruning in development. Findings of the capabilities of infants in processing features of language, numbers, and objects that were discussed at the start of this chapter provide some support for the selectionist viewpoint by showing that basic building blocks of cognition are present at or near birth. The second principle posits that correlated firing of cells leads to increased connections between them (Hebb, 1983). This principle ensures that cells that fire together will be strongly represented in connections. It has been used to support the constructivist view (e.g., Quartz and Sejnowski, 1997), in which development is seen as progressive increase in the representational properties of the cortex. The environment shapes the specific organization of sensory systems tuned to visual, auditory, or other aspects of stimuli. In support of this view is evidence that children deprived of sensory input (e.g., deaf from

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

birth) show specific alterations in the organization of other senses (Neville, 1995). This view stresses how learning organizes brain circuits. But whether through pruning or through circuit organization, both views converge on the importance of experience in shaping the physiology of the brain.

Neuroimaging

It is now possible to observe changes in the brain in normal subjects as they perform tasks involving thought and emotion (Posner and Raichle, 1994; Thatcher et al., 1996). The development of methods of imaging the human brain increases our ability to observe and study how it changes with experience.

When neurons are active, they change their own local blood supply. This makes it possible to track areas of the brain active during cognitive processes by methods designed to study changes in blood flow. The two most prominent methods for doing this are positron emission tomography (PET) and functional magnetic brain imaging (fMRI). These two methods are fully complementary and have usually provided converging evidence when applied to cognitive studies (Posner and Raichle, 1994, 1998).

A major achievement of brain imaging studies has been consistent localization of brain areas that perform particular functions or mental operations, including precise localization of the processing of motion, color, shape, and other object features in the human visual cortex. For high-level cognitive tasks, the almost universal finding has been the activation of networks of small numbers of often widely separated brain areas. Subjects of early pedagogy, such as listening, remembering, searching visual arrays, processing music, learning sequences of spatial locations, and reading, have been among the tasks studied by neuroimaging. In the case of reading, these have reflected known features of the task, such as synthesis of letters into word chunks, input and output phonology, semantic association, grammatical markers, etc. Meta-analysis based on combining data across studies and laboratories has proven an important vehicle for summarizing the almost overwhelming number of results obtained from studies conducted in the past 10 years (for reviews see Posner and Raichle, 1994, 1998).

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

For example, a recent meta-analysis (Bush et al., 1998, 1999) has shown that many tasks involving the selection of cognitive and emotional information activate separate but adjacent areas of the anterior cingulate gyrus along the midline of the frontal lobe. The area activated by emotional input has strong connections to the amygdala and other emotional brain centers. In some situations, the cognitive and emotional brain areas appear to be mutually inhibitory (Drevets and Raichle, 1998). Studies of the growth and development of this area in childhood (Casey et al., 1997a, 1997b) suggest a role in self-monitoring and the regulation of behavior. While much needs to be learned about the organization, relation, and function of these areas, the discovery of adjacent cognitive and emotional brain areas in the cingulate provides general support for the importance of appropriate emotion and cognitive input during development.

Plasticity

Plasticity refers to the ability of the brain to modify over time in response to change. The change might be major—as when a section of the brain is damaged in an accident—or minor—as when the brain changes in response to daily experience. The use of neuroimaging methods has provided some interesting vignettes, however. A few minutes of practice at generating associations for a particular word, for example, has been shown to shift activity from one brain pathway to another (Raichle et al., 1994). This work has begun to allow us to consider different physiological mechanisms for many of the types of changes that are likely to be involved in child learning and education.

Recent research indicates some of the ways in which a person’s own activity, or learning from external events, might work to change brain circuitry on a temporary or permanent basis. The findings of the most relevant research are highlighted below.

  • Attention allows rapid amplification of blood flow in local brain areas performing computations in high-level skills (Corbetta et al., 1993). By giving priority to some computations, attention can serve to reprogram the circuits by which tasks are executed.

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

In high-level skills (like reading), several years appear to be required to develop attentional systems that perform the required regulatory functions (Posner and Rothbart, 1998). While the orienting of attention appears to develop in the first year of life (Johnson, 1998; Johnson et al., 1991), ages 3 to 5 appear to be very important in the achievement of the kind of attentional control needed for high-level skills (Posner and Rothbart, 1998).

  • Priming is produced by the presentation of a sensory event (e.g., a visual or auditory word) that changes the pathway so that new stimuli that share some or all of that pathway will be processed more efficiently. Apparently this is done by the prime tuning neurons involved in the processing of the sensory, phonological, and semantic codes of the word, so that fewer neurons are required by the subsequent target (Ungerleider et al., 1998).

  • Research on practice by Raichle et al. (1994) has shown that the anatomical area for generating the use of a word changes when the same word list has been practiced for a few minutes. When generation has become automated with practice, it uses the same circuit as skilled readers use to read words aloud. When dealing with a new word, several cortical areas become involved that drop out with practice. However, automating the learning of entirely new words requires much longer practice.

  • In a recent study of learning 40 lexical items in a new artificial language, it took 20 to 50 hours of practice before the same superiority in reaction time was shown for the items that is usually found for reading the native language (McCandliss et al., 1997).

  • The brain area that represents English orthography (rule learning) within the visual system (visual word form) appears to require some years to develop and, once developed, may be strongly resistant to change (McCandliss et al., 1997).

The plasticity of the brain is not a characteristic that is confined to the early years of life. Nevertheless, the rapid growth of the brain in the early years provides an opportunity for the environment to play an enormous role in development. The findings from research on the brain suggest that helping children to pay attention, as well as the particular tasks to which their attention is drawn, will influence circuit development in the brain. And by

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×

providing opportunity for repetition (of routines, stories, and activities that promote social and cognitive skill development) and practice of valued skills, the brain becomes more efficient in those areas, freeing attention for higher-order thinking.

SUMMARY

Early childhood is a period of tremendous cognitive, social, and emotional growth. While there do appear to be systemic stages of development that place a ceiling on what a child can do or learn, beneath that ceiling there is significant variation among children, and across domains in a given child. The window into the developing brain allows us to see that stimulation from the environment changes the very physiology of the brain, with implications for cognitive, social, and emotional growth.

The ability of the environment to substantially alter developmental outcomes in the early years suggests the potential for preschool programs to have a powerful impact on child development. But a large research base supports the notion that if that impact is to be positive, preschool programs must attend to cognitive, social, and emotional development simultaneously. We addressed the importance of children’s early relationships with adults, emphasizing that emotionally secure relationships are crucial in early education and care settings and are predictive of children’s social relations with peers, their manifestation of behavior problems, and school achievement when they are older.

The thrust of the research reviewed above suggests that development is not simply an unfolding of innate capacity, but varies with context. It is a dance in which nature—what the child brings into the world—and nurture—the relationships and other aspects of the child’s context—are partnered. Because nature and nurture are unique for every child, we observe remarkable variation among children even at very early ages. The research reviewed above suggests that responsiveness of those in the nurturing role to the developmental level and characteristics of the child is key to supporting further development. We therefore turn our attention in the next chapter to some of the central aspects of variation among preschool-age children to which an attentive adult might respond.

Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 37
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 38
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 39
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 40
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 41
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 42
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 43
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 44
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 45
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 46
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 47
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 48
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 49
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 50
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 51
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 52
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 53
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 54
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 55
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 56
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 57
Suggested Citation:"2 What Does the Science of Learning Contribute to Early Childhood Pedagogy?." National Research Council. 2001. Eager to Learn: Educating Our Preschoolers. Washington, DC: The National Academies Press. doi: 10.17226/9745.
×
Page 58
Next: 3	The Importance of Individual and Cultural Variations »
Eager to Learn: Educating Our Preschoolers Get This Book
×
Buy Paperback | $49.95 Buy Hardback | $69.95
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

Clearly babies come into the world remarkably receptive to its wonders. Their alertness to sights, sounds, and even abstract concepts makes them inquisitive explorers—and learners—every waking minute. Well before formal schooling begins, children's early experiences lay the foundations for their later social behavior, emotional regulation, and literacy. Yet, for a variety of reasons, far too little attention is given to the quality of these crucial years. Outmoded theories, outdated facts, and undersized budgets all play a part in the uneven quality of early childhood programs throughout our country.

What will it take to provide better early education and care for our children between the ages of two and five? Eager to Learn explores this crucial question, synthesizing the newest research findings on how young children learn and the impact of early learning. Key discoveries in how young children learn are reviewed in language accessible to parents as well as educators: findings about the interplay of biology and environment, variations in learning among individuals and children from different social and economic groups, and the importance of health, safety, nutrition and interpersonal warmth to early learning. Perhaps most significant, the book documents how very early in life learning really begins. Valuable conclusions and recommendations are presented in the areas of the teacher-child relationship, the organization and content of curriculum, meeting the needs of those children most at risk of school failure, teacher preparation, assessment of teaching and learning, and more. The book discusses:

  • Evidence for competing theories, models, and approaches in the field and a hard look at some day-to-day practices and activities generally used in preschool.
  • The role of the teacher, the importance of peer interactions, and other relationships in the child's life.
  • Learning needs of minority children, children with disabilities, and other special groups.
  • Approaches to assessing young children's learning for the purposes of policy decisions, diagnosis of educational difficulties, and instructional planning.
  • Preparation and continuing development of teachers.

Eager to Learn presents a comprehensive, coherent picture of early childhood learning, along with a clear path toward improving this important stage of life for all children.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text.

    « Back Next »
  6. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  7. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  8. ×

    View our suggested citation for this chapter.

    « Back Next »
  9. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!