Jean Piaget (1896-1980) was one of the great creative intellects of this century. His theory has had massive impact on the thinking and behavior of all of those who deal with children, including researchers, parents, teachers, day care workers, therapists, and those who design products and services for children. His theory has inspired thousands of research studies, innovations in curriculum and instruction, and new approaches by parents to the intellectual development of their children. These effects show every sign of continuing into the next century. Although his theory is familiar to many, it is not always well-understood.

Unlike the perspectives discussed earlier in this chapter, Piaget's theory focuses almost exclusively on cognitive development. It explains how children develop knowledge of their world, how they think and solve problems, and how these cognitive processes change in a stage by stage progression from birth to maturity. Thinking is an extraordinarily complicated process, and Piaget developed an extraordinarily complicated theory to explain the process. Fully understanding this theory demands years of study, a task well beyond our scope here. The next few paragraphs are intended merely to provide an initial overview.


Piaget portrayed the child as innately and irrepressibly active, acting upon their environment rather than simply reacting to it. Action is, therefore, assumed as a spontaneous and universal quality central to the cognitive development of all children. Children are by nature curious and explorative, persistently seeking novelty, and try to incorporate that novelty into their understanding of the world. Infants express the active nature of their cognitive system by exploring every object within their reach. Older children express this active quality in persistence in problem solving and intellectual curiosity.

Piaget assumed that children do not passively wait for other people to present problems to them; they actively seek problems to solve. It is just in their nature to be curious, inquisitive, and interested in novelty. In practical terms, those who deal with children should assume that, irrespective of age or stage, all children are intrinsically motivated to improve their understanding of the world around them. Optimal cognitive development requires a rich environment that can be actively explored for novelty and challenge. In this view, rigidity of thought, passivity, and lack of curiosity are considered abnormal states that require explanation. Unfortunately, Piaget's theory offers little explanation for children who appear intellectually unmotivated and slow to learn.


The central focus of Piaget's theory is the concept of structure. He used the term structure in two ways. First, he suggests that all aspects of the real world are structured entities. In the world of an infant, for example, individual objects such as rattles, blankets, and mother's face have structure. In the expanded world of the preschool child, the arrangement of toys on a shelf, friendships with peers, and problems encountered in preschool have structure. Still later in development, children must solve structured math problems in school and engage in structured social relationships. In this use of the term, structure refers to the complexity of some aspect of the environment.

Piaget's second use of the term structure refers to cognitive structures--the mental units that children use to represent reality, to think about the objects, events, and relationships in their experience, and the strategies they use to solve problems. Put simply, cognitive structures are the way the child knows the world. A child knows the world to the extent that he or she has cognitive structures that match the structure of objects and events in the real world. Piaget's theory is an explanation of the development of cognitive structures from infancy through adolescence, and how cognitive structures facilitate adaptation to the environment.

Adaptation is the process by which cognitive structures are applied to and are modified by the child's experiences. Piaget defined two distinct processes by which adaptation occurs: assimilation and accommodation. In assimilation, a child uses an existing cognitive structure to interpret some experience. For instance, when a familiar rattle is presented to an infant, she shows that she knows the rattle by grasping it and shaking it to make a rattling sound. Piaget would say that the infant has assimilated the rattle to the cognitive structure of "things-that-shake-and-make-noise". However, the infant may subsequently grasp a pacifier, assimilate it to the same cognitive structure, and shake it in anticipation of the sound. The new object has been interpreted as if it were an instance of "rattle". Thus assimilation interprets the new in terms of the old.

In accommodation, the child modifies an existing cognitive structure to conform to some new aspect of reality. For instance, for young infants a rattle is at first just one more object to be grasped and all objects are assimilated to the cognitive structure for grasping. After repeated experience with rattles and other objects, though, the infant modifies the cognitive structure and begins to distinguish between rattles and non-rattles. Thus accommodation represents developmental change in cognitive structures--an integration of the new into the old.

Piaget viewed the mind as never completely satisfied with its current level of understanding of objects, events, or relationships. Every act of assimilation implies some degree of accommodation to some heretofore unnoticed feature of reality. The result is an improved adaptation to that reality. Thus cognitive structures are always moving gradually but steadily toward better and better approximations of reality.


Piaget described cognitive development as a series of qualitative changes in the way children think and solve problems from infancy through adolescence. He identified four stages of cognitive development, each with its own unique form of cognitive structure. Each new structural form derives from the previous form, but with new and more sophisticated capabilities. Piaget believed that all children in all cultures progress through these stages in exactly the same sequence and that no one ever skips a stage. However, some children progress through the stages more quickly than others, and those who progress more slowly may never reach the final stage.

Piaget's four stages are described briefly below. As with the theories of Freud and Erikson, more detailed accounts of development within each stage will be provided in appropriate chapters later on in the text.

Sensori-motor Stage (0-24 months) The sensori-motor stage, is characterized by action-oriented problem solving. At the beginning of this stage, the newborn's cognitive organization is limited to an elaborate set of "wired-in" reflexes such as startling in response to a loud noise or turning the head toward a stroke on the cheek. As newborns actively touch, taste, and visually scan the world around them, though, they develop what Piaget called sensori-motor schemas--simple cognitive structures that regulate the infant's body movements and the effects of those movements on objects. For example, the grasping schema organizes the infant's voluntary opening and closing of his or her hands and the grasping and manipulation of objects. In time, they accommodate these primitive schemas into more sophisticated schemas that enable them to influence their environment in increasingly complex ways. For instance, they accommodate their aimless arm and hand movements in the first three or four months into movements that manipulate the environment by pushing, squeezing banging, tearing, lifting, and crushing by six to eight months. By the end of the first year they use their arms and hands to manipulate simple instruments such a fork or spoon, a milestone of sensori-motor intelligence.

Preoperational Stage (ages 2-6) The action-oriented problem solving of the sensori-motor stage is gradually replaced by thought that is mediated by words and images. Piaget called this thought symbolic reasoning. Children will engage in increasingly complex forms of symbolic reasoning as they develop from childhood to adolescence. Piaget named each of the remaining stages after the form of symbolic reasoning that characterizes each stage: In the preoperational stage, preschoolers reason with preoperations (or preconcepts); In the concrete operational stage school-age children reason with concrete operations; and in the formal operational stage, adolescents' reason with formal operations.

During the preoperational stage, children no longer are limited to thinking about the objects in their immediate perceivable environment. They can now organize mental images of events and objects both present and absent into primitive concepts (or preoperations) that they can use to solve simple problems. For example, preschoolers know what toys they own and where they are at all times, and use that knowledge to organize their play.

Although preoperational thought represents a quantum leap from earlier sensorimotor thought, it has many limitations. One is a tendency to focus on isolated parts of an event rather than seeing the whole picture. Piaget called this centration. For instance, after meeting the new teacher at day care, a preschooler may be unable to remember what she looks like but remembers her earrings in great detail. Another limitation of preoperational thought is that it is often illogical. Parents and practitioners are alternately frustrated and entertained by the preschooler's confused concepts of time, space, classification, and quantitative relationships. For example, when preschool children are asked to retell a story read to them, they tend to reverse sequences of events, confuse cause and effect, and mistake appearance for reality.

Perhaps the most serious limitation of preoperational thought, however, is its irreversibility. Preschool children can literally think their way into a problem but are unable to reverse their thought process. That helps to explain why young children take things apart, but have a great deal of difficulty putting those things back together. Thus, while preoperational thought represents a great step forward beyond sensorimotor thought, it fails to provide a logical, systematic way of adapting to the world.

Concrete Operations (ages 7-11) During the concrete operations stage, children's thinking becomes increasingly logical. The new form of cognitive structure, the concrete operation, organizes thoughts into logical systems. For example, children gradually come to understand that adding, subtracting, multiplying, and dividing are interrelated mathematical operations, and that classes are composed of subclasses. They also begin to understand logical relationships--for instance, if three sticks of different length are displayed, a child will reason that if the first stick is longer than the second stick, and the second is longer than the third, then the first stick must be longer than the third stick. Concrete operational thought is reversible, allowing the child to think his or her way into problems and back out. For example, an eight-year-old is much more likely than a five-year-old to think about how he is going to put something back together before he takes it apart.

The child does well with such problems because they involve concrete items that are familiar to the child. If, however, the problem involves abstract concepts or objects with which the child is not familiar, the child does poorly. For example, if a child is told (with no objects present) that "A" is greater than "B," and that "B" is greater than "C," the child is unlikely to conclude that "A" must be greater than "C." At this stage the child can deal only with real objects that can be seen and touched. Abstract concepts of hypothetical events and outcomes are still beyond the child's capability.

 Formal Operations (age 12 and beyond) The hallmark of the formal operations stage is the abilty to consider general propositions and principles and to think about hypothetical events. For the first time, the individual can reason about phenomena that do not exist in reality, such as abstract concepts of morality, science, and mathematics. Once individuals enter the formal operations stage, they are also able to think about thinking--both their own thinking and other people's. This capability is an enormous advantage in communication and social relationships. For instance, when a formal operational teenage boy wants to meet a certain teenage girl, he can think about what she might be thinking about him and plan his behavior accordingly.

Although Piaget proposed four stages, he noted that not everyone reaches the stage of formal operations. At each stage of development, children must have access to appropriately challenging experiences. Children who are deprived of these experiences will develop more slowly than other children and are unlikely to fulfill their full intellectual potential.


Piaget's theory satisfies some criteria of good theory better than others. Despite his use of highly abstract terms and concepts, Piaget's detailed descriptions of children's behavior have helped communicate the meaning of his concepts to researchers and practitioners. While Piaget and other researchers have had little difficulty testing the theory in thousands of research studies, his more abstract concepts have proven difficult to research. Significant questions remain concerning the generalizability of his concepts. For example, it is unclear whether his descriptions of stages hold up across children in different cultures and socio-economic status. More positively, Piaget's theory is good "developmental" theory. Piaget's detailed descriptions of the gradual accumulation of age-related changes in specific content areas are exemplary.

The great strength of Piaget's theory lies in its broad view of cognitive development. Piaget presented both general principles that integrate all cognitive functioning and detailed descriptions of development in numerous content domains, such as logic, language, morality, causality, time, space, number, seriation, and classification, to name just a few. His theory has stimulated thousands of research studies over the last thirty years, and it has spawned several spin-offs, including the provocative work of Robbie Case (1978) and Kurt Fischer (1980).

Piaget's theory has also had significant impact on the practice of child development. His detailed accounts of descriptions of development in specific content areas has helped educators develop new curriculum and approaches to instruction at all age levels. His concept of the child as an active learner has encouraged teachers to gear instruction to children's intrinsic motivation and natural curiosity.

But Piaget's work has significant weaknesses. Some of his concepts--such as assimilation and accommodation--are highly abstract and difficult to tie directly to children's behavior. How do we know when a child is accommodating in a learning situation? What criteria should we use to determine when a cognitive structure has changed? Other concepts--particularly some of his notions of formal operational reasoning--have not been verified by research.

Despite its shortcomings, Piaget's theory has transformed our understanding of child development and will continue to influence researchers and practitioners well into the next century.

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PIAGET's theory:


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