You know a lot of things. Two and two is four. Alaska is the largest U.S. state. George Washington was the first president. You also know how you know these facts: People taught them to you, and you committed them to memory. Now consider some other things you know:

How did you learn these things? It’s unlikely that a biology teacher ever taught you the one about horses and zebras, yet you know it is true. And when did you learn them? Were you born with such knowledge, or did you acquire it gradually during childhood? Questions like these are the focus of study in cognitive development.

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Any review of cognitive development must begin with the monumental contributions of Jean Piaget, among the most influential figures in the history of psychology (Haggbloom et al., 2002). Piaget was trained as a biologist. But a job working with children aroused his interest in a psychological question: How do children’s thinking abilities develop? To find out, he studied young children (including his own) from the 1920s until his death in 1980.

Piaget achieved scientific breakthroughs that were not appreciated immediately. However, English-language summaries of his findings, particularly that of John Flavell (1963, 1996), spread the word. By the 1980s, “almost everything people think and do” in cognitive development “had some connection with questions that Piaget raised” (Flavell & Markman, 1983, p. viii).

PIAGET’S METHOD. Piaget devised a research method that was simple yet powerful. It had two key features (Flavell, 1963):

SCHEMAS AND OPERATIONS. How can children solve problems they have never seen before? Piaget’s answer is simple. Anything a person does—from picking up a toy to solving a math problem—requires that person to possess some mental structure that makes the action possible. Psychological abilities, Piaget reasoned, are like biological abilities. For example, because people digest food, they must possess a biological structure that enables digestion of that food. Analogously, if they solve a psychological problem, they must possess a mental structure that enables that type of problem to be solved.

Piaget called these mental structures schemas. A schema, in Piagetian theory, is a mental structure that makes organized, meaningful action possible. A schema for grasping enables an infant to grab hold of a variety of toys. A schema for dogs enables a child to point to a picture of a dog in a book when asked to do so. A schema for proportions (i.e., relations between two amounts; Boulanger, 1976) enables an older child to figure out that a car that takes 15 minutes to travel 2 miles is faster than a car that takes 10 minutes to travel 1 mile. Once in possession of the schemas, children can grasp toys, identify dogs, and solve proportion problems that they have never come across before.

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Schemas enable children to engage in operations (Piaget, 1964), which are actions that modify an object or set of objects. The modification can be physical (e.g., arranging objects from smallest to largest) or conceptual (e.g., placing words in alphabetical order). Operations are reversible; the logical system used in the operation can go in two directions (objects can be ordered from largest to smallest or placed in reverse alphabetical order). Operations, to Piaget, are “the essence of knowledge” (1964, p. 20). Knowledge therefore consists of not merely facts, but the ability to do things: to conduct operations using schemas.

ASSIMILATION AND ACCOMMODATION. People use their schemas to adapt to the environment. Piaget’s theory highlights two processes of adaption: assimilation and accommodation.

In assimilation, external events are incorporated into an existing schema; children think about events and act on objects in ways that reflect the schemas they possess. If a child with a grasping schema used previously on toys grasps an adult’s eyeglasses, she is assimilating eyeglasses to her grasping schema. If a child with a schema for chickens sees a Thanksgiving turkey and says, “Cluck, cluck, chicken,” he is assimilating the turkey to his chicken schema.

Accommodation is the modification of schemas as a result of environmental feedback. In accommodation, schemas change. If, in the preceding example, adults explain that “no, it’s a turkey, not a chicken,” the child will eventually accommodate to the environment by dividing his original one schema into two: a chicken schema and a turkey schema. Experience, then, increases the number and precision of children’s schemas.

Piaget’s theory of schemas, assimilation, and accommodation addresses two questions of interest to all psychologists. The first is the nature–nurture question (see Chapters 1 and 4): Do psychological qualities originate in inherited biology (nature) or environmental experience (nurture)? Piaget’s approach is neither a strict “nature” nor a strict “nurture” position. Rather, it uniquely mixes the two. The child learns by experience; in accommodation, “nurture” refines schemas. But children’s mental powers (e.g., the ability to store and use schemas) have a biological origin, consistent with a “nature” perspective (Flavell, 1996).

The second question is the relation between learning and development. In some other psychological theories, “development” refers merely to changes in behavior that result from learning (see Chapter 7). Learning, in this view, drives development. But Piaget thought this was backward; he believed that development—specifically, the development of mental schemas—drives learning. Children spontaneously modify and elaborate their schemas as they interact with the world. The development of these knowledge structures, in turn, enables them to learn from parents and teachers.

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STAGES OF DEVELOPMENT. Piaget claimed that cognitive development occurs in a fixed series of steps, or stages. A developmental stage is a period of time (months or years) during which one form of thinking is predominant. In a stage theory of development, the child is said to maintain one level of development for a given time period, and then to transition relatively rapidly to a new, higher level. Metaphorically, development is like a flight of stairs rather than a ramp: There are discrete steps, traversed in a fixed order.

Piaget proposed four stages of development: the (1) sensorimotor, (2) preoperational, (3) concrete operational, and (4) formal operational stages (Table 14.1).

In the sensorimotor stage (birth to 2 years), the child interacts with the world through his or her sensory systems (e.g., hearing, vision) and systems for motor movement (e.g., sucking, grasping). Children at this stage are preverbal; they cannot think in words. Although they cannot formulate a thought such as “I’d like to play with my new toy,” they can see the new toy and play with it. Schemas involving sensation and motor movement enable purposeful action.

During the sensorimotor stage, children develop a concept you normally take for granted: object permanence. Object permanence is the understanding that objects continue to exist even when they can no longer be seen or otherwise perceived. Early in the sensorimotor stage, infants lack this capacity. If they are playing with a toy and an adult covers it with a piece of cloth, they will be baffled and won’t look under the cloth for the toy. Later in the sensorimotor stage, they will. The child must develop a conception that the object still exists, despite being out of sight.

In the preoperational stage of development (ages 2 to 7), children can use mental symbols—words, numbers, images—to think. The capacity to use symbols is a major step “up” in development. Yet at this stage, the child still cannot engage in operations. Recall that operations are reversible (e.g., items can be ordered from small to large or large to small). In the preoperational stage, children cannot make these logical reversals. This mental limitation is strikingly demonstrated by the phenomenon of conservation.

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Conservation, in Piagetian psychology, is the recognition that an object maintains some essential physical properties even when it is physically transformed. In other words, those properties are conserved. Suppose you spread a ball of dough into a flat pizza. If you recognize that this spreading does not give you any more (or less) dough, then you have exhibited conservation; you know the dough’s mass is conserved in spite of the transformation of its shape. Conservation requires a reversible mental operation. You must be able to see that going back and forth—from ball to flat pizza and back—does not alter physical mass.

Piaget discovered that, in the preoperational stage, children are not capable of conservation. They cannot perform the reversible mental operations needed to understand that physical properties are conserved. In a classic demonstration, Piaget poured water from a short, wide beaker into a tall, narrow one and asked children whether the amount of water was the same or different (Figure 14.1). “Different,” they said! Children in the preoperational stage use a simple physical cue, the height of the water, to judge how much water there is; they thus believe more water is present when the liquid is poured into the narrow beaker.

In the concrete operational stage of development (ages 7 to 11), the child can perform reversible logical operations. Many of these operations have the same structure as basic arithmetic: adding and subtracting; judging that amounts are greater or lesser than one another; dividing groups into subgroups of items. If shown a group of six cats and two dogs and asked if there are more animals than there are cats, the child in the concrete operational stage can solve the problem; that child recognizes that cats are a subgroup of a larger group, animals. In earlier stages, however, children cannot perform this mental operation and are likely to say that there are more cats. Thanks to the ability to perform reversible operations, children in the concrete operational stage of development can begin to solve the conservation problems described earlier.

A mental limitation in the concrete operational stage is that children can execute operations only on objects, that is, things that actually exist in the child’s experience. In the formal operational stage (age 11 through adulthood), they can execute operations on both actual objects and hypothetical ones. Questions about blue unicorns and flying dogs (e.g., if there are six blue unicorns and two flying dogs, are there more animals than dogs?) can be contemplated logically, even though the objects do not exist. The child thinks about hypothetical objects by applying abstract rules. For example, if asked to think of a number that has the following property—the number, plus 20, is twice itself—the formal operational child does not have to rely on trial-and-error guessing, as the concrete operational child would. A child in the formal operational stage of development can apply the rule that for any number x, if x + y = 2x, then x = y, so the number must be 20 (Ault, 1977).

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Piaget recognized that children reach the stages at different ages; diverse experiences might accelerate or slow development. However, he claimed that the stages occur in a fixed order. You can’t skip any. The ordering reflects the logical relation among stages. To engage in concrete operational thinking, you first have to be able to think using symbols (the achievement of preoperational thought). To engage in formal operational thinking, you first have to be able to think using operations (the achievement of concrete operational thought).

Answer: 1dhi, 2b, 3aef, 4gc

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Piaget’s contributions are of unparalleled importance. Yet developmental psychology has moved beyond his contributions. Contemporary research suggests that Piaget overlooked a factor critical to children’s cognitive development: domains.

In the study of cognition, a domain is an area of knowledge and mental ability (Hirschfeld & Gelman, 1994). For example, knowledge about plants (e.g., that they grow, need water, and are not manmade) and about household objects (e.g., that they do not grow or need watering and are manmade) would be two separate domains. The ability to use language (see Chapter 8) or to appreciate and produce music (Justus & Hutsler, 2005) similarly may be distinct domains.

Piaget’s theory was domain-general; that is, his theoretical principles were meant to generalize across domains. When Piaget said a child was, for example, in the concrete operational stage of development, he expected the child to exhibit concrete operational thinking, no matter what the topic of the child’s thought.

Research challenges this expectation of Piagetian theory. In particular domains of thinking, children seem “smarter”—that is, engage in more complex thinking processes—than Piaget would expect (Bloom, 2004; Wellman & Gelman, 1992). Let’s look at three of these domains: thinking about (1) objects, (2) living things, and (3) people’s minds.

OBJECTS. Piaget found that, in infancy, children lack object permanence. They seem to have no understanding that there is such a thing as an object with a permanent, fixed existence. Recent research, however, reveals that they understand more than Piaget had thought. Much of this modern research uses a valuable research tool that was not employed by Piaget: looking-time studies (see Research Toolkit).

RESEARCH TOOLKIT

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As the developmental psychologist Paul Bloom (2004) reviews, results of looking-time studies reveal that infants are surprised if any of the following events happen:

Their surprise indicates that they held expectations. The infants expected that objects were coherent wholes (not a collection of pieces that would break off); that they moved continuously (and thus couldn’t jump from one barrier to another); and that they had a permanent existence, were solid, and could not move spontaneously. The infants could not put their knowledge into words. Nevertheless, their expectations reveal that they possessed knowledge of objects, despite being in the Piagetian sensorimotor period.

LIVING THINGS. A second domain about which young children display surprising amounts of knowledge is livings things. Piaget expected that children younger than school age would not be able to form the abstract mental category “living things” and thus would not recognize, for example, that their baby sister is alive, needs food, and sleeps, whereas their baby doll does not. Again, however, more recent evidence reveals that Piaget underestimated young children’s knowledge. As Wellman and Gelman (1992) review:

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PEOPLE AND THEIR MINDS. Children also display more knowledge than Piaget expected when they think about the human mind. Even at a young age, children know that the people they encounter have minds, and that the plants and toys they encounter do not. Children possess a theory of mind, an understanding that other people have feelings and thoughts (Wellman, Cross, & Watson, 2001).

Evidence of theory of mind comes from a cleverly designed experimental task (Wimmer & Perner, 1983). Children of varying ages are shown a series of pictures: Someone places an object in one location and then leaves the vicinity (Figure 14.3). While the first person is away, a second person moves the object to a different location. Children are asked to indicate where the first person will look for the item when she returns. Yes, it’s easy for you—but not for very young children. To know where the person will look, you have to have a theory of mind. You must understand that she has personal beliefs that guide her actions and that her beliefs are acquired from experience.

Ability to perform this task correctly develops during the preschool years (Wellman et al., 2001; Wimmer & Perner, 1983). At age 3, children cannot get it right; they think that, upon returning, the person will look for the object in its actual, new location. By age 6, more than half of children get the problem correct, and by age 8 to 9, the vast majority of children answer it correctly.

Other research shows that substantial elements of a theory of mind are in place even earlier (Wellman & Gelman, 1992). If asked why someone is looking in a particular location for an object, 4-year-olds will explain the action in terms of beliefs (“She thought it was there”).

Many researchers suggest that theory of mind is central to a disorder of psychological development, autism. More formally known as autism spectrum disorder, autism refers to a range of symptoms whose central features include impaired communication and social interaction with other people (National Institute of Mental Health, 2011). Children with autism might, for instance, focus their attention on objects while failing to establish eye contact with other people. Children who lack a theory of mind, and thus fail to understand that others have feelings and thoughts, may be those who experience symptoms of autism (Baron-Cohen, Leslie, & Frith, 1985). Research shows that individuals with autism perform particularly poorly on tests of the ability to automatically make inferences about other people’s beliefs (Schneider et al., 2013).

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Novel research findings prompt psychologists to develop novel theories. Let’s consider two attempts to move beyond Piagetian theory. The first proposes the existence of innate mental structures.

INNATE MENTAL STRUCTURES. As you’ve seen, children possess domain-linked knowledge—about objects, living things, and the mind—that is hard to explain from a Piagetian perspective. Piaget thought that ideas were learned by experience. But children develop complex beliefs at such an early age that it’s hard to see how experience alone could account for their mental abilities. Parents, for example, rarely try to teach their children that other human beings have minds, yet kids somehow seem to know this.

Research on domain-linked knowledge prompts many contemporary developmental psychologists to conclude that Piaget underestimated the role of nature. They propose that children possess mental structures—elements of mind that enable them to interpret the world—that are products of biological inheritance. These inherited mental structures enable them to think accurately about objects, animate living things, and other people’s minds.

One theory of innate mental structures has been developed by Harvard psychologist Susan Carey (2009, 2011). She proposes that children possess innate input analyzers, that is, biologically inherited mental mechanisms designed to detect and process specific types of information. The type of information corresponds to the domains of knowledge we have just reviewed. For example, an innate input analyzer that detects agents (entities that have goals and pursue them through their actions) contributes to children’s ability to distinguish animate living things from objects as well as to their development of a theory of mind.

SOCIAL AND CULTURAL EXPERIENCE. A second alternative to Piagetian theory is grounded in the work of Lev Vygotsky, a Russian psychologist living in the first third of the twentieth century (Daniels, Cole, & Wertsch, 2007). Vygotsky believed that Piaget underestimated the importance of social and cultural experience and provided a theory of cognitive development that put sociocultural factors in their proper place.

In Piagetian theory, development primarily is an individual process. The lone child encounters the world, puzzles through various experiences, and thus advances in logical thinking. But Vygotsky notes that much development occurs through social interaction. Children acquire the cognitive tools of their culture—language, counting, reading, writing, mathematical symbols, diagrams, flowcharts, musical notation—by interacting with adults and older peers (Wertsch, 2007).

Once children have practice using cultural tools, they internalize them (Vygotsky, 1978). What first was a social activity becomes a feature of the child’s inner mental life. Consider language. At first, it is a way to communicate with others. But once learned, it dominates inner thoughts; people “talk to themselves” in sentences and internal dialogues (Hermans, 1996). This inner speech serves important functions. Children gain control over their behavior by listening to instructions (e.g., “Timmie, don’t touch the stove”) and internalizing them (“I must not touch the stove”; see Meichenbaum, 1977).

Unlike Piaget, Vygotsky (1978) thought that children, at any given time, should be characterized at two developmental levels: their current level of cognitive development and their potential level. Potential levels are mental achievements children cannot reach by themselves, but that they can reach through interacting with others who support them (e.g., with hints, examples, or leading questions). Vygotsky called the region between the two levels the zone of proximal development. This zone, then, contains problems the child cannot do independently, yet can do collaboratively (Figure 14.4). Vygotsky encouraged educators to challenge learners with problems in their zone of proximal development. Doing so, he said, would speed learning and psychological development.

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Children often learn through zone-of-proximal-development interactions (Rogoff, 1990). When mothers explain classifications among animals (e.g., a house cat and a lion are both cats) while reading to children, the children’s ability to categorize animals improves. When parents provide strategies for remembering words, children’s memory improves. When children work together on logic problems and discuss their thoughts about the problem, they become more skillful problem solvers.

In summary, Vygotsky showed how the development of the mind is enhanced by the social experiences of the person. In so doing, he uncovered key connections between person and mind, and between social and cognitive development.

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You have learned that social experience spurs cognitive development. This psychological fact leads to a biological prediction: Environmental experience also should spur the biological development in the brain because the brain is the organ of cognition. Let’s now move to a biological level of analysis to see if this prediction holds true.

ENVIRONMENTAL ENRICHMENT AND BRAIN DEVELOPMENT. How could you find out whether environmental experience enhances brain development? Ideally, you would run an experiment: Raise individuals in different environments and then measure their brains. The experiment, unethical with humans, has been conducted with animals.

Researchers (e.g., Jurgens & Johnson, 2012) have raised mice in environments that vary in enrichment, that is, the degree to which the environment contains complex physical stimuli (tunnels, ladders) and social stimuli (other mice). After a period of development, the brains of these mice are compared with others who are raised in a low-enrichment environment that lacks these stimuli. Research shows that the brains of the two groups of mice differ (Markham & Greenough, 2004). Enriched environments produce brains in which:

These results demonstrate a key fact about the brain (also see Chapter 3). The exact structure of the brain, for any organism, is a product of both inheritance and experience. Just as physical exercise builds stronger muscles, the mental exercise that occurs in enriched environments builds a stronger brain.

THE DEVELOPMENT OF SUBSYSTEMS OF THE BRAIN. Another psychological fact suggests another prediction about brain development. Psychologically, as you learned, children experience a sequence of stages; at one stage they cannot perform tasks that, at a later stage, are easy for them. This suggests that the brain should develop through a sequence of stages, too.

It does. “In general, the sequence in which the cortex matures parallels cognitive milestones in human development” (Casey et al., 2005, p. 104). To understand the brain’s maturation, you have to recall that the brain contains different parts that specialize in different tasks (e.g., understanding language, processing visual images, generating emotions, thinking about oneself). It turns out that these different parts develop in a fixed sequence. Consider three regions of the brain: (1) sensorimotor cortex (involved in basic perceptual processes and motor movement), (2) parietal and temporal cortices (whose many functions include language processing), and (3) prefrontal cortex (critical to sustaining attention on tasks and controlling emotional impulses). Brain research indicates that (Casey et al., 2005; Figure 14.5):

No wonder Piaget discovered a sensorimotor stage at which children can think, but not in words. At this Piagetian stage, children’s sensorimotor cortex is developed, but language-processing regions of the brain are not. Contemporary brain research thus complements Piaget’s earlier psychological research. Similarly, research on neural development shows, at a brain level of analysis, why children have more difficulty controlling emotions than adults do: Their prefrontal cortex, which is needed to control emotions, is less developed.

THE DEVELOPMENT OF BRAIN NETWORKS. The brain’s specialized parts are interconnected. Nerve cells link distinct neural systems, creating information networks within the brain (Sporns, 2010). When people engage in complex mental activities, such as solving a problem, multiple interconnected regions of their brains are active (Gerlach et al., 2011).

A major feature of brain development is that, over time, these networks change (Fair et al., 2009). In childhood, most of the brain’s connections are “local”; that is, they interconnect neurons within one region of the brain. Later in life, connections become “global”; different regions of the brain become more strongly interconnected (Khundrakpam et al., 2013).

Advances in brain imaging let us see these interconnections. Researchers obtained brain images in two groups of people: children aged 7 to 9 and adults aged 19 to 22 (Uddin et al., 2011). They focused on connections between two regions of the brain:

As you can see in Figure 14.6, the two brain regions do not change significantly from childhood to adulthood. But the interconnections between them do (Uddin et al., 2011). The connections are stronger—thicker and more elaborate—in adulthood than in childhood.

What is the psychological implication of this biological finding? The brain connections enable people to gain greater control over their thoughts, emotions, and behavior (Menon & Uddin, 2010). Early in life, when the connections are weak, children may respond in a quick, reflexive manner to environmental events that grab their attention. For example, a child who is supposed to be doing homework might become distracted by a toy or by even slight feelings of hunger. Later in life, people are better at controlling what they pay attention to and concentrating on problems to be solved. This greater control is due, in part, to the stronger connections between the brain’s central executive and attentional networks.

In sum, brain research deepens our understanding of cognitive development. As children age and interact with the world, their growing cognitive abilities are accompanied by growth in the biological systems of the brain (Figure 14.7).

Cognitive abilities are not the only aspects of life that change with development. People also develop emotions and motivation, the ability to control their emotions and behavior, and a sense of self—an understanding of who they are and their place in the world. These topics are studied in the field of social development, which we turn to next, beginning with the start of social life: infancy.

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