11.3 Three Theories of Children's Mental Development

As children grow from infancy toward adulthood, their thinking becomes ever more logical, ever more effective in solving problems. How can these changes be characterized, and what are the processes through which they develop? Here we shall address these questions from three theoretical perspectives. The first is Piaget’s theory, which focuses on the child’s actions on the physical world as a driving force for cognitive development. The second is Lev Vygotsky’s sociocultural theory, which focuses on the child’s interactions with other people as a driving force. The third is the information-processing perspective, which accounts for mental development in terms of maturational changes in basic components of the child’s mind.

Piaget’s Theory: Role of the Child’s Own Actions in Mental Growth

In his long career at the University of Geneva (from the 1920s until his death in 1980), Jean Piaget wrote more than 50 books and hundreds of articles on children’s reasoning. His goal was to understand how the adult mind, particularly its capacity for objective reasoning, develops from the child’s more primitive abilities. His primary methods were those of observation, testing, and questioning. From his observations of children’s conversations and play, he would extract clues about their understanding. He would also present children with specific tasks to solve and question them about their reasons for the solutions they offered. From this work, Piaget developed an elaborate, comprehensive theory of cognitive development.

Piaget’s fundamental idea was that mental development derives from the child’s own actions on the physical environment. According to Piaget, children are constantly, in their play and exploration, striving to figure out what they can do with the various objects that exist in their world. By acting on objects, children develop mental representations, called schemes, which are mental blueprints for actions. More specifically, Piaget used the term schemes to refer to a mental representation of a bodily movement or of something that a person can do with an object or category of objects. The earliest schemes, according to Piaget, are closely tied to specific objects and are called forth only by an object’s immediate presence. Thus, a young infant might have a sucking scheme most applicable to nipples, a grasping and shaking scheme most applicable to rattles, and a smiling scheme most applicable to human faces. As children grow older, they develop new, more sophisticated, more abstract schemes that are less closely tied to the immediate environment or to actual physical actions. They become schemes for mental actions.

Schemes Develop Through Assimilation and Accommodation

Piaget conceived of the growth of schemes as involving two complementary processes: assimilation and accommodation.

Assimilation is the process by which new experiences are incorporated into existing schemes. Piaget was a biologist by training, and he considered the assimilation of experiences to be analogous to the assimilation of food. Two people may eat the same type of food, but the food will be assimilated into the tissues differently, depending on the inner structures involved in digestion and building the body.

Jean Piaget Because of his interest in the influence of the environment on children’s cognitive development, Piaget preferred to observe children in natural settings. Here he is shown during a visit to a nursery school.

Bill Anderson/Science Source

Moreover, just as nondigestible foods will not result in body growth, new experiences that are too different from existing schemes to be mentally digested will not result in mental growth. A calculator given to an infant will not contribute to the child’s arithmetic skills because the infant has no calculating scheme into which to assimilate the calculator’s functions. Instead, the infant will probably assimilate the calculator into his or her already well-developed sucking scheme or banging scheme.

Few new stimuli perfectly fit an existing scheme. Assimilation usually requires that existing schemes expand or change somewhat to accommodate the new object or event. Appropriately, Piaget referred to this process as accommodation. In Piaget’s theory, the mind and its schemes are not like a brick wall, which just grows bigger as each new brick (unit of knowledge) is added; they are more like a spider’s web, which changes its entire shape somewhat as each new thread is added. The web accommodates to the thread while the thread is assimilated into the web. The addition of new information to the mind changes somewhat the structure of schemes that are already present.

Children Behave Like Little Scientists

In Piaget’s view, infants and children at play behave like little scientists. Their exploratory play—in which they manipulate objects in all sorts of ways to see what happens—can be thought of as experimentation. They are most strongly motivated to explore those objects and situations that they partly but do not fully understand. Stated differently, in Piaget’s terms, they are most drawn to experiences that can be assimilated into existing schemes, but not too easily, so that accommodation is required. This natural tendency leads children to direct their playful activities in ways that maximize their mental growth.

Accommodation This 11-month-old may be accommodating her “stacking scheme” to assimilate the experience of one block fitting inside another, From such experiences, a new “fits inside” scheme may develop.

Jaren Wicklund/YAY Micro/Agefotostock

Consider, for example, an infant who already has a scheme for stacking objects, which includes the notion that an object placed on top of another will remain on top. One day this infant happens to place an object above an open container and, instead of remaining on top, the object falls into the container. This observation is intriguing to the infant because it seems to violate his stacking scheme. As a result, the infant may spend lots of time dropping various objects into various containers. Such exploration eventually leads the infant to modify (accommodate) his stacking scheme to include the notion that if one object is hollow and open-topped, a smaller object placed over its top will fall inside. At the same time, other schemes that include the notion that two objects cannot occupy the same place at the same time may also undergo accommodation.

As another illustration of the little scientist concept, consider an experiment performed by Laura Schulz and Elizabeth Bonawitz (2007). These researchers presented preschool children (ages 4 to 5), one at a time, with a box that had two levers sticking out of it. Pressing one lever caused a toy duck to pop up through a slit on top of the box, and pressing the other lever caused a puppet made of drinking straws to pop up. The box was demonstrated to different children in two different ways. In one demonstration condition, each lever was pressed separately, so the child could see the effect that each lever produced when pressed. In the other condition, the two levers were always pressed simultaneously, so the child could not know which lever controlled which object. After the demonstration, each child was allowed to play with the two-lever box or with a different toy.

The result was that children who had only seen the two levers operated simultaneously chose to play much more with the demonstrated box than with the new toy, while the opposite was true for the other children. The logical interpretation is this: The children who could see, from the demonstration, what each lever did were no longer much interested in the box because they had little more to learn from it. In contrast, those who had only seen the two levers pressed simultaneously wanted to play with the box so they could try each lever separately and discover whether it moved the duck, or the puppet, or both. Consistent with Piaget’s theory, the children’s play was oriented toward discovery, not toward repetition of already known effects.

Reversible Actions (Operations) Promote Development

As children grow beyond infancy, according to Piaget, the types of actions most conducive to their mental development are those called operations, defined as reversible actions—actions whose effects can be undone by other actions. Rolling a ball of clay into a sausage shape is an operation because it can be reversed by rolling the clay back into a ball. Turning a light on by pushing a switch up is an operation because it can be reversed by pushing the switch back down. Young children perform countless operations as they explore their environments, and in doing so, they gradually develop operational schemes—mental blueprints that allow them to think about the reversibility of their actions.

Understanding the reversibility of actions provides a foundation for understanding basic physical principles. The child who knows that a clay ball can be rolled into a sausage shape and then back into a ball of the same size as it was before has the basis for knowing that the amount of clay must remain the same as the clay changes shape—the principle of conservation of substance. The child who can imagine that pushing a light switch back down will restore the whole physical setup to its previous state has the basis for understanding the principle of cause and effect, at least as applied to the switch and the light.

Four Types of Schemes; Four Stages of Development

Piaget conceived of four types of schemes, which represent increasingly sophisticated ways of understanding the physical environment. His research convinced him that the four types develop successively, in stages roughly correlated with the child’s age (see Table 11.1).

Table 11.1: Table 11.1
Piaget’s theory: Periods and characterics

The Sensorimotor Stage The most primitive schemes in Piaget’s theory are sensorimotor schemes, which provide a foundation for acting on objects that are present but not for thinking about objects that are absent. During the sensorimotor stage (from birth to roughly 2 years of age), thought and overt physical action are one and the same. The major task in this stage is to develop classes of schemes specific for different categories of objects. Objects the child explores become assimilated into schemes for sucking, shaking, banging, squeezing, twisting, dropping, and so on, depending on the objects’ properties. Eventually the schemes develop in such a way that the child can use them as mental symbols to represent particular objects and classes of objects in their absence, and then they are no longer sensorimotor schemes.

The Preoperational Stage Preoperational schemes emerge from sensorimotor schemes and enable the child to think beyond the here and now. Children in the preoperational stage (roughly from age 2 to 7) have a well-developed ability to symbolize objects and events that are absent, and in their play they delight in exercising that ability (Piaget, 1962). Put a saucepan into the hands of a preschooler, and it is magically transformed into a ray gun or a guitar—the saucepan becomes a symbol in the child’s play. The schemes at this stage are called preoperational because, although they can represent absent objects, they do not permit the child to think about the reversible consequences of actions.

According to Piaget, understanding at the preoperational stage is based on appearances rather than principles. If you roll a ball of clay into a sausage shape and ask the child if the shape now contains more than, less than, or the same amount of clay as before, the child will respond in accordance with how the clay looks. Noting that the sausage is longer than the ball was, one preoperational child might say that the sausage has more clay than the ball had. Another child, noting that the sausage is thinner than the ball, might say that the sausage has less clay. (For another test of operational thinking, see Figure 11.6.)

Figure 11.6: A test of conservation of substance Although she knew that the two tall glasses contained the same amount of liquid and watched the contents of one glass being poured into the short glass, this child still points to the tall glass when asked, “Which has more?” She uses perception rather than logic to answer the question.

Both: Ellie Miller

The Concrete-Operational Stage Although (or perhaps because) preoperational children have not yet internalized an understanding of operations, they continually produce operations as they explore their environment. As they push, pull, squeeze, mix, and so on, they gradually develop concrete-operational schemes and eventually enter the concrete-operational stage (roughly from age 7 to 12). These schemes permit a child to think about the reversible consequences of actions and thereby provide the basis for understanding physical principles such as conservation of substance and cause and effect (Piaget, 1927).

A concrete-operational child who has had experience with clay will correctly state that the sausage has the same amount of clay as the ball from which it was rolled because it can be rolled back into that ball. A concrete-operational child who has had experience with bicycles will correctly say that the chain is crucial to the bicycle’s movement but the fender is not because the child can picture the reversible consequences of removing each and knows that the pedals can move the wheels only if there is a physical connection between the two.

The earliest schemes for operations are referred to as concrete because they are still tied closely to the child’s actual experiences in the world. The child might have schemes, for example, for the conservation of clay rolled into various shapes and of fluids poured from one container to another but still lack an understanding of conservation of substance as a general principle that applies regardless of the type of substance.

The Formal-Operational Stage During the concrete-operational stage, the child begins to notice certain similarities about the operations that can be performed on different entities. For instance, the child who understands that that the amount of clay remains the same no matter what shape it is molded into, and that the amount of water remains the same no matter what the shape of the glass it is poured into, may begin to understand the principle of conservation of substance as a general principle, applicable to all substances. In this way, according to Piaget, the child develops formal-operational schemes, which represent abstract principles that apply to a wide variety of objects, substances, or situations. When such schemes characterize a significant portion of a person’s thinking, the person is said to be in the formal-operational stage (which begins roughly at the onset of adolescence and continues throughout adulthood). Formal-operational schemes permit a person to think theoretically and apply principles even to actions that cannot actually be performed (Inhelder & Piaget, 1958).

With formal operations, adolescent can contemplate not just things that “are” (that is, concrete entities), but also things that might be, such as world peace, universal religion, or changes in the legal system. They can “think about thinking” and extend principles into hypothetical realms that neither they nor anyone else has actually experienced. While the concrete-operational reasoner is limited to empirical (fact-based) science and arithmetic, the formal-operational reasoner is capable of theoretical (principle-based) science and formal mathematics.

Criticism of Piaget’s Theory of Stages

Historically, Piaget’s theory played a valuable role in motivating developmental psychologists to focus more closely than they had before on children’s actions and on the ways that those actions promote mental growth. The concepts of assimilation and accommodation and the idea that operations contribute significantly to cognitive development are still much valued by many developmental psychologists. Especially valued is the general idea that children actively build their own minds through their exploration of the world around them.

The most frequent criticisms of Piaget’s theory today center on his concept of developmental stages (Kohler, 2008). Piaget himself acknowledged that the transitions from stage to stage are gradual, not abrupt. His own research convinced him that each new type of scheme develops slowly, over the course of years, and that a child at any given point in development might use a more advanced type of scheme for one class of problems while still using a more primitive type for other problems. Subsequent research, however, has led many developmental psychologists to reject the whole concept that people think in fundamentally different ways at different ages.

Much research suggests that Piaget underestimated the mental abilities of infants and young children and overestimated those of adolescents and adults. Earlier in this chapter you read about violation-of-expectation experiments showing that infants as young as 3 months expect objects to continue to exist when out of view, contrary to Piaget’s assertion that infants in the sensorimotor stage cannot think of absent objects. Children as young as 4 or 5 years can pass at least some tests of concrete-operational reasoning if the problems are presented clearly, without distracting information, and with words that the child understands (McGarrigle & Donaldson, 1975; Siegler & Svetina, 2006).

Piaget has had a greater impact on developmental psychology than any other person. As one scholar quoted by Harry Beilin (1992) put it, “assessing the impact of Piaget on developmental psychology is like assessing the impact of Shakespeare on English literature or Aristotle on philosophy—impossible” (p. 191). Although many details of Piaget’s theory are questioned today, he uncovered many important phenomena, and while his account of development is not fully accurate, it provides a reasonable picture of the behavior of most children most of the time and a good jumping-off point for further investigation.

Vygotsky’s Theory: Role of the Sociocultural Environment in Mental Growth

Children do not develop in a social vacuum. They develop in a sociocultural milieu in which they interact constantly with other people and with products of their cultural history. The person most often credited with originating the sociocultural perspective on cognitive development is Lev Vygotsky, a Russian scholar who died in 1934 at age 38, after devoting just 10 years to formal research and writing in psychology.

Vygotsky (1934/1962) agreed with Piaget that the main force for development is the child’s active interaction with the environment, but he disagreed with Piaget’s conception of the relevant environment. Whereas Piaget emphasized the child’s interaction with the physical environment, Vygotsky emphasized the child’s interaction with the social environment. In Vygotsky’s view, cognitive development is largely a matter of internalizing the symbols, knowledge, ideas, and modes of reasoning that have evolved over the course of history and constitute the culture into which the child is born.

The distinction between Vygotsky’s and Piaget’s perspectives can be illustrated by applying those perspectives to a story, told by Piaget (1970), about how a mathematician friend of his had, as a child, become fascinated by mathematics:

The story is prototypically Piagetian. The child, through acting on physical objects (pebbles), discovers and is exhilarated by a core principle of mathematics (commutativity). As Piaget goes on to explain, “The knowledge that this future mathematician discovered that day was drawn, then, not from the physical properties of the pebbles, but from the actions that he carried out on the pebbles.”

How might Vygotsky have reacted to this story? It was told long after Vygotsky had died, but we imagine him saying: “Where did that young boy learn to count in the first place? Of all the things he might do with pebbles, why did he decide that counting them was worthwhile? The answer lies in the boy’s social environment. He was growing up in a culture where number words are in the air and people value counting. He may have discovered with pebbles that day the principle of commutativity, but his social environment had prepared him to make that discovery.”

Tools of Intellectual Adaptation

Vygotsky believed that children learn to think, in part, as a function of the tools of intellectual adaptation that their culture provides. Number words are such tools, as are alphabets in some literate cultures, and also pencils, books, abacuses, calculators, and computers. Children may still discover concepts such as commutativity through their active manipulation of objects, but they do so with the tools their culture provides them, and usually with the implicit assistance of significant others in their local environment.

Consider the way a culture’s language represents numbers and how that may influence quantitative thinking. The languages of many hunter-gatherer groups contain very few number words. For instance, the language of the Pirahã of Brazil has only three number words, which, translated to English, are one, two, and more than two. The Pirahã do not count. In one experiment, tribe members were shown sets of nuts containing from one to nine nuts. Then the researcher placed the nuts in a can and drew them out one by one while asking, as each nut was removed, if any nuts were left in the can. Most of the tribe members were correct for one, two, or three nuts, but were incorrect for larger sets (Gordon, 2004). If the Pirahã wanted to keep exact counts of things or to think mathematically, they would have to start by inventing or learning number words. Pirahã children, however, who learn Portuguese, are able to do addition and subtraction with larger quantities, supporting the view that it is the language’s ability to represent numbers that is responsible for the pattern of numerical thinking in these cultures (Gordon, 2004).

A more subtle linguistic effect on numerical reasoning may lie in the comparison of people who speak English or certain other European languages with those who speak Asian languages such as Chinese, Japanese, and Korean. Asian children greatly outperform American and European children in mathematics at every stage of their schooling. Usually that effect is attributed to differences in how mathematics is taught, but some researchers have argued that the difference may stem at least partly from a difference in language (Miller et al., 1995; Miura & Okamoto, 2003).

In English and other European languages the number words do not precisely mirror the base-10 number system that is used in all of arithmetic, but they do so in Chinese, Japanese, and Korean. While we count one, two, …, nine, ten, eleven, twelve, thirteen, …, twenty, twenty-one, …, the speakers of the Asian languages count (if their words were translated literally into English) one, two, …, nine, ten, ten one, ten two, ten three, …, two-tens, two-tens one, …. The words eleven and twelve give the English-speaking child no clue at all that the number system is based on groups of 10, whereas ten one and ten two make that fact abundantly clear to the Asian child. Even many English-speaking adults do not know that teen means “ten” (Fuson & Kwon, 1992), and children do not automatically think of twenty as “two tens.” Because the Asian words make the base-10 system transparent, Asian children might develop an implicit grasp of that system and thereby gain an advantage in learning arithmetic.

American children lag behind East Asian children in mathematical ability Although there are numerous reasons for this difference, one seems to be the way European and Asian languages represent numbers.

©The New Yorker Collection, 1998, Mike Twohy, from cartoonbank.com. All Rights Reserved.

Consider children learning to add two-digit numbers—say, 34 plus 12. English-speaking children pronounce the problem (aloud or to themselves) as “thirty-four plus twelve,” and the words give no hint as to how to solve it. Chinese-speaking children, however, pronounce the problem (in effect) as “three-tens four plus ten two,” and the words themselves point to the solution. In the two numbers together, there are four tens (three tens plus one ten) and six ones (four plus two), so the total is four-tens six (forty-six).

Consistent with this view, a number of experiments have shown that children who speak Asian languages have a much better implicit understanding of the base-10 system, even before they begin formal mathematics training, than do children who speak European languages. In one experiment, for example, 6-year-olds in the United States, and in France and Sweden (where number words contain irregularities comparable to those in English) were compared with 6-year-olds in China, Japan, and Korea on a task that directly assessed their use of the base-10 system (Miura et al., 1994). All the children had recently begun first grade and had received no formal training in mathematics beyond simple counting.

Each was presented with a set of white and purple blocks and was told that the white blocks represented units (ones) and the purple blocks represented tens. The experimenter explained, “Ten of these white blocks are the same as one purple block,” and set out 10 whites next to a purple one to emphasize the equivalence. Each child was then asked to lay out sets of blocks to represent specific numbers—11, 13, 28, 30, and 42. The results were striking. The Asian children made their task easier by using the purple blocks correctly on over 80 percent of the trials, but the American and European children did so on only about 10 percent. While the typical Asian child set out four purples and two whites to represent 42, the typical American or European child laboriously counted out 42 white blocks. When they were subsequently asked to think of a different method to represent the numbers, most of the American and European children attempted to use the purple blocks, but made mistakes in about half the trials.

Differences in the way languages represent numbers actually reflect quite subtle differences in how a culture’s tools of intellectual adaptation can influence how children learn to think. Consider the drastic changes in technology that occurred over the latter part of the twentieth century and into the current one. Computers and the many related devices (smart phones, iPads) and formats change the way children learn to think and transform them into very different adults. Recall our discussion in Chapter 10 of the Flynn effect, the continual increase in IQ scores over the course of the twentieth century. Flynn (2012) argued that the increase is due mainly to changes in modern life, including greater use of technology.

Most college students today, and certainly nearly all who will follow them, are digital natives, people who grew up with digital media and take them for granted. Older people who grew up in the age before desktop computers (including your two authors) can learn to use the new technology, but rarely find that it comes easily or spontaneously to them. Computer (and smart phone) literacy is like a first language for most people under 40 today, whereas it is like a second language to most people over 40. Such differences in the availability of computers at an early age surely affect how people learn to think.

Vygotsky proposed that children’s thinking does not develop in a vacuum but is inherently sociocultural. It is affected by the values, beliefs, and tools of intellectual adaptation found in a child’s culture. Because these values and intellectual tools can vary substantially from culture to culture, and within a culture over time, Vygotsky believed that neither the course nor the content of intellectual growth was as “universal” as Piaget and others had assumed.

The Role of Collaboration and Dialogue in Mental Development

Vygotsky’s fundamental idea is that development occurs first at the social level and then at the individual level. People learn to converse with words (a social activity) before they learn to think with words (a private activity). People also learn how to solve problems in collaboration with more competent others before they can solve the same kinds of problems alone. Vygotsky (1935/1978) coined the term zone of proximal development to refer to the realm of activities that a child can do in collaboration with more competent others but cannot yet do alone. According to Vygotsky, children’s development is promoted most efficiently through their behavior within their zones of proximal development (Gauvain, 2013).

In research at an alternative, age-mixed school, Jay Feldman and I (Peter Gray) found many examples of collaboration between adolescents and younger children that nicely illustrate Vygotsky’s concept of a zone of proximal development (Gray & Feldman, 2004). In one case, for example, a teenage boy helped a 5-year-old girl find her lost shoes by asking her to think of all the places she had been that day and all the places where she had already looked. Through such suggestions, the teenager added structure to the little girl’s thinking, which allowed her to think and search more systematically than she would have been able to do on her own. Such collaboration not only enabled the child to find her shoes but also probably promoted her mental development by suggesting questions that she might ask herself to guide future searches for missing objects.

From a Vygotskian perspective, critical thinking—in adults as well as children—derives largely from the social, collaborative activity of dialogue. In actual dialogue, one person states an idea and another responds with a question or comment that challenges or extends the idea. In the back-and-forth exchange, the original statement is clarified, revised, used as the foundation for building a larger argument, or rejected as absurd. From many such experiences we develop the capacity for internal self-dialogue so that we (or what may seem like voices within us that represent our friends and critics) question and extend our own private thoughts and ideas and in that way improve them or throw them out. Consistent with Vygotsky’s view, researchers have found that students who engage in covert dialogues with authors as they read, or who explain ideas they are studying or logic problems they are working on to other people, real or imagined, acquire a more complete understanding of what they are reading or studying than do students who do not engage in such activities (Chi et al., 1989, 1994; Heiman, 1987; Mercer & Littleton, 2007).

In the zone This boy may not be quite ready to repair his bicycle himself, but he can with a little help and advice from his dad. Vygotsky pointed out that skill development often occurs best when children collaborate with more-skilled others to do things that are within the child’s zone of proximal development.

©Ariel Skelley/Corbis

The Child as Apprentice

While Piaget’s child can be characterized as a little scientist performing experiments on the world and discovering its nature, Vygotsky’s child can be characterized as an apprentice (Rogoff, 1990, 2003). Children are born into a social world in which people routinely engage in activities that are important to the culture. Children are attracted to those activities and seek to participate. At first their roles are small, but they grow as the children gain skill and understanding. From this view, cognitive development is a progression not so much from simple tasks to more complex ones as from small roles to larger roles in the activities of the social world. Barbara Rogoff (1990, 2003) has documented many ways by which children in various cultures involve themselves in family and community activities and learn from those activities.

One prediction of the apprenticeship analogy is that people who grow up in different cultures will acquire different cognitive abilities. A child surrounded by people who drive cars, use computers, and read books will not learn the same mental skills as a child surrounded by people who hunt game, weave blankets, and tell stories far into the night. The apprenticeship analogy also reminds us that logic itself is not the goal of mental development; the goal is to function effectively as an adult in one’s society. To achieve that goal, children must learn to get along with other people and to perform economically valuable tasks. In our society, such tasks may involve for some people the kind of mathematical and scientific reasoning that Piaget labeled formal-operational; but in another society, they may not.

An Information-Processing Perspective on Mental Development

As you have just seen, developmental psychologists in the tradition of Piaget and Vygotsky attempt to understand how children’s interactions with their physical or social environment increase their knowledge and lead to new ways of thinking about the world around them. In contrast, developmental psychologists who adopt the information-processing perspective attempt to explain children’s mental development in terms of operational changes in basic components of their mental machinery.

The information-processing approach to cognition, as described in Chapter 9, begins with the assumption that the mind is a system, analogous to a computer, for analyzing information from the environment. According to the standard information-processing model (refer back to Figure 9.1 on p. 322), the mind’s machinery includes attention mechanisms for receiving information, working memory for actively manipulating (or thinking about) information, and long-term memory for passively holding information so that it can be used in the future. As children grow, from birth to adulthood, their brains continue to mature in various ways, resulting in changes in their abilities to attend to, remember, and use information gleaned through their senses.

Development of Long-Term Memory Systems: Episodic Memory Comes Last

In Chapter 9 we discussed in the phenomenon of infantile amnesia, the inability to remember events and experiences before the age of 3 or 4. The reason for this is that before this age, children do not have well-developed explicit, or declarative, memory, which requires a degree of self-awareness and abstract encoding that develop gradually over childhood. However, implicit memories, which affect behavior even though the person is unable to report them, are available even to young infants. Implicit memories include procedural memories, such as how to pound with a hammer or ride a bicycle, and effects of classical and operant conditioning, which are demonstrated in nonverbal behavior.

As a demonstration of implicit memory in young infants, consider a study by Carolyn Rovee-Collier and her colleagues. A 2-month-old who learns to kick with one leg to move a mobile and who then, a day later, kicks again as soon as the mobile appears, demonstrates implicit memory of how to operate the mobile (see Figure 11.7). Rovee-Collier and her colleagues found that 2-month-olds, who received just a few minutes’ experience with moving a mobile by kicking, remembered the response as much as 4 months later if given occasional reminders (in which they saw the mobile but did not have a chance to operate it) (Rovee-Collier & Cuevas, 2009).

Figure 11.7: A test of infants’ implicit procedural memories The infant, as young as 2 months of age, learns to operate the mobile by kicking one leg (a). During the test, on another day, the mobile is again presented, but now the ribbon is connected to another hook, so the infant can’t control the mobile (b). The infant’s immediate kicking in this condition is a sign of long-term memory for how to control the mobile.

Both: Courtesy of Dr. Carolyn Rovee-Collier

Research suggests that young children must develop the ability to encode their experiences into words before they can form episodic memories of those experiences (Bauer, 2013; Richardson & Hayne, 2007). Recall our earlier discussion of the “Magic Shrinking Machine” study by Simcock and Hayne (2002) in Chapter 9, in which toddlers remembered a novel event only if they had a sufficiently sophisticated vocabulary at the time of the experience, irrespective of their language ability 6 months later when they were questioned about the event. At about age 3 children begin, with some reliability, to talk about their experiences as they experience them. Such talk seems to help them make sense of what they are doing, as we noted earlier, and it may also be essential to the formation of episodic memories. At first such talk depends on the existence of an older conversation partner who can help the child organize the experience in a coherent way and find the appropriate words for it. In one study, researchers recorded the conversations of mothers and their 3-year-old children at visits to a natural history museum and then, a week later, asked the children to recall what they had seen at the museum (Tessler & Nelson, 1994). The result was that the children correctly recalled only those items that had been commented on jointly by both the mother and child in conversation. Items that had been commented on just by the mother or just by the child were not recalled.

Many other research studies have shown that the ability to form detailed, long-lasting episodic memories increases gradually throughout the years of childhood and reaches a plateau in late adolescence or young adulthood (Ofen et al., 2007; Piolino et al., 2007). This improvement is accompanied by continued maturation of the brain, particularly in the prefrontal lobes (Ofen et al., 2007). As noted at the end of Chapter 9, connections between the prefrontal lobes and other portions of the brain seem to be crucial to the formation and recall of episodic memories.

The Development of Basic-Level Processes: Executive Function

Recall from Chapter 5 and Chapter 9 that executive functions are mental processes involved in the regulation of thought and behavior, and most researchers propose that there are three related components to executive function: working memory (or updating); inhibition; and switching (or cognitive flexibility) (Miyake & Friedman, 2012). Related to each of these is the speed with which we can process information. These basic-level cognitive abilities play a critical role in most higher-level cognitive tasks, and so understanding how they develop during childhood is important for understanding how children acquire culturally important abilities such as reading and mathematics (Carlson, Zelazo, & Faja, 2013).

Forming episodic memories To form long-term episodic memories, young children must encode their experiences verbally. Such encoding is facilitated by adults who share the experience and, through conversation, help the child to find words for what he or she sees.

Christopher Allan/Getty Images

Many experiments, using many different sorts of measures, have shown that the amount of either verbal or visual information that a person can hold in working memory at any given time increases steadily throughout childhood and reaches adult levels at about age 15. For instance, the number of digits or random single-syllable words that a person can hold in mind and repeat, after hearing them just once, increases from about three at age 4 to about seven at age 15 (Gathercole et al., 2004). These increases are accompanied by improved performance on standard tests of fluid intelligence (Kail, 2007; Swanson, 2008).

Figure 11.8: Dimensional Card Sorting Task Children are asked to sort cards initially by one dimension (for example, color) and later by a second dimension (for example, shape). Children much younger than 4 years of age have difficulty on the “switch” trials and usually continue to sort by the original dimension.

(Adapted from Zelazo & Rapus, 1996.)

Children’s inhibition abilities, as well as the ability to resist interference, show marked improvements over childhood. Inhibition tasks used with young children include variants of the familiar game “Simon Says” (children must only perform an action when Simon says so—for example, “Simon says, ‘Touch your nose’“); the tapping task, in which children must tap once each time the examiner taps twice and tap twice each time the examiner taps once; and the opposites task, pointing to one of two pictures an interviewer did not point to (Baker et al., 2010).

Young children often have a difficult time inhibiting their speech. For instance, in one study children were shown a picture book and asked to name only certain pictures on a page—pictures of people, for example—and not to name others, such as pictures of animals (Kipp & Pope, 1997). Kindergarten children showed no tendency to inhibit their responses, mentioning one set of items (animals) as frequently as the other (people), despite seeming to understand the instructions to do otherwise. One 4-year-old we know had particular difficulty with inhibiting his speech. While relating what had happened at preschool that day, he quickly shifted to talking about something on a TV show he had seen recently. Realizing his sudden change of topic, he said, “Oops, I interrupted myself.”

Young children also have difficulty shifting from one task or set of rules to another (Hanania & Smith, 2009). In a simplified variant of the Wisconsin Card Sorting Task (Chapter 9, p. 337), called the Dimensional Card Sorting Task, developed by Philip Zelazo and his colleagues (1996), children are shown a set of cards with simple pictures drawn on them, much like those shown in Figure 11.8. The cards depict either automobiles or flowers, which are either red or blue. In the “shape game,” children are to put all the automobile cards in one pile and the flowers in the other. In the “color game,” they are to put all the red cards in one pile and the blue ones in the other. Three-year-olds easily can play either the shape or the color game, but things become more complicated when, after playing one game, they are told to switch to the other: If they had been sorting by shape, they are now told to sort by color and vice versa. They are reminded of the rule and even asked to state it, which they can do. Nevertheless, most 3-year-olds continue to sort by the old rule, failing to switch to the new rule despite being able to state it. Most 4-year-olds, however, can switch rules appropriately.

Young children often have a difficult time not saying whatever is on their minds.

Baby Blues by Rick Kirkman and Jerry Scott. Copyright 2013 Baby Blues Partnership. Dist. by King Features Syndicate.

We should also note that changes in executive function occur at the other end of the life-span continuum. In older adults, declines have been observed in each aspect of executive functions—working memory, inhibition, and task switching (Goh et al., 2012; Passow et al., 2012; Wasylyshyn et al., 2011).

Figure 11.9: Reaction time for simple tasks decreases with age Children and adolescents were tested for their speed on six different tests, including a test of elementary reaction time (releasing a button in response to a signal) and a test of picture matching (judging whether two pictures are identical or not). Each person’s average time for the six tests was converted by dividing it by the average time achieved by young adults, and the results were then averaged for each age group. Note that a decline in reaction time implies an increase in speed.

(Based on data from Kail, 1993.)

Closely correlated with each of these measures of executive function is speed of processing—the speed at which elementary information-processing tasks can be carried out. Speed of processing is usually assessed with reaction-time tests that require a very simple judgment, such as whether two letters or shapes flashed on a screen are the same or different, or whether an arrowhead is pointing right or left.

Such tests consistently reveal age-related improvement in speed up to about 15 years of age (Kail, 1993, 2007; Wassenberg et al., 2008; see Figure 11.9). As discussed in Chapter 10, faster processing speed permits faster mental movement from one item of information to another, which improves one’s ability to keep track of (and thereby hold) a number of different items in working memory at once. Faster processing speed may result at least partly from the physical maturation of the brain that occurs throughout childhood, independent of specific experiences. Consistent with that view, 9- and 10-year-old boys who were judged as physically mature for their age—on the basis of their height as a percentage of their predicted adult height—exhibited significantly faster reaction times than did boys of the same age who were judged as physically less mature (Eaton & Ritchot, 1995).

As we mentioned in Chapter 9, the prefrontal cortex plays a major role in executive functions (Miller & Wallis, 2012) and is one of the last brain areas to fully develop. Performance on a variety of executive-function tasks has been found to be significantly correlated with the development of the prefrontal cortex from infancy through adolescence (Bell et al., 2007; Luna et al., 2001). For example, neuroscientist Beatriz Luna and her colleagues (2001) examined brain activity using fMRI of subjects between the ages of 8 and 30 while they performed a variety of inhibition tasks. The researchers reported that the adolescents showed greater levels of neural activity in the prefrontal cortex than in either children or adults. Although task performance increased gradually with age, brain activation in the frontal cortex on this task increased sharply between childhood and adolescence, only to decrease again in adulthood.