Jean Piaget (1896-1980) was one of the most famous scholars in the history of psychology. His focus on fundamental issues concerning how knowledge develops is still relevant and has a great deal to offer current and future approaches in psychology. Yet determining this relevance for our understanding of child development is difficult because he is a paradoxical figure.
Although Piaget was very influential, publishing some 100 books and 600 papers based on uncounted studies with his collaborators, he is also one of the most misunderstood and criticized authors in psychology. Progress in science requires criticism, but to be beneficial it should be based on solid understanding. Unfortunately, much of the well-known criticism in current textbooks and blogs tends to be based on misinterpretations of Piaget’s work.
One reason why Piaget was so commonly misunderstood also reflects why his approach is still important, fitting well with current thinking in developmental psychology. He challenged preconceptions that were taken for granted by adopting a radically different worldview: that intelligence develops because we are naturally enactive, interactive, and embodied, and that these factors influence how we interact with, and learn about, the world. This view is consistent with current theory in cognitive science. Thus, Piaget’s approach is not just historical, it established a fruitful foundation for later research.
Piaget is perhaps best known for suggesting that there are four distinct stages of cognitive development, which refer to different and increasingly complex forms of thinking through which children progress. But he later regretted this focus on stages because he understood that it is more important to understand the process through which children move from simple to more complex forms of thinking. This became his theory of how knowledge develops; understanding it is essential to examining his view of knowledge.
To understand Piaget’s theory, it is crucial to appreciate the questions that concerned him. He was interested in how human thinking develops, especially scientific thinking. Piaget referred to his work as genetic epistemology, a term that has been misunderstood by some textbook authors as referring to genes, which is the current meaning of genetic. However, when Piaget coined the term in the 1920s, genetic (or the French genese) referred to genesis, as in origin and development. Epistemology refers to the study of knowledge. Thus, Piaget conceptualized the discipline of genetic epistemology as the study of how knowledge develops.
Central to this concept is how humans develop the ability to think – for example, how we plan for the future or reflect on the past. Genetic epistemology considers how children develop new knowledge. Some knowledge is certain or necessary; consider the way that understanding that two plus two is necessarily four, or that the number of objects in a group remains the same as long as objects are not added or taken away, even if they are moved around or counted in different ways.
Piaget’s question regarding the development of scientific thinking could be studied by examining its history, and he did explore this topic. But his question can also be addressed by studying children as they develop more complex knowledge and ways of thinking. Piaget initially thought he would study children for a few years, but he ended up devoting much of his extensive career to researching child development, from when he first earned a PhD in biology at age 21 to shortly before his death at 84.
Any theory of how children develop forms of thinking is based on assumptions about how they learn about their world, so the presupposition regarding how we come to know reality should be examined. Many psychologists assume that we learn about the world just by opening our eyes and knowledge floods in. This seems to fit with our intuitions. If we imagine a scene, we might think of it as a match to a landscape we have seen. This is the idea that we know the world through representing it. It reflects the common view that knowledge is based on passively forming mental representations that match the world, much like copies. These representations can either be derived from experience (empiricism) or be innate (nativism).
Although these two approaches differ in the source of knowledge, they agree that this knowledge is a set of representations of the world. Piaget (1970) labelled this approach the copy theory of knowledge, while his American contemporary, John Dewey (1929), criticized it as the spectator view of knowledge (see Chapman, 1999).
However, if the only way we know the world is through representing it, then the only way to check such a representation is to compare it with another representation. But this does not help us check whether this knowledge is correct because that can only be done by checking the representation against reality. We would need some independent way to do that.
Thus, this representational theory of how knowledge works assumes that we already have knowledge, and it does not explain how we come to know about the world. Thus, it is flawed and an alternative is needed. Piaget’s theory is built on resolving this problem, but if researchers are not aware of the circularity of the copy theory, then the rest of Piaget’s alternative may seem unnecessary.
If knowledge is not a matter of representation, then how can we successfully navigate the world without bumping into parts of it? The fact that we can interact successfully with world suggests a better view of human intelligence –that is, infants and children acquire knowledge through activity. They learn about what they can do with objects, as well as other people, and what happens in response. As a result of repeated experiences, they come to know the world in terms of their increasing ability to anticipate what will happen when they act.
In framing this action-based view of knowledge, Piaget endorsed a view known as constructivism, according to which children come to understand the world through learning what they can do with it. This view involves learning to anticipate what will happen when we do something. Thus, perception, according to Piaget, is not just a passive process. To see a hammer is not just having an image of the tool on the eye’s retina; it involves understanding the potential to interact with the hammer, that is, as an object for grasping and hitting nails (or for an infant, wooden pegs).
Piaget challenged preconceptions that tend to be taken for granted and in their place worked within a constructivist, or action-based, worldview. The word constructivism has been used by a variety of theorists, so readers should carefully assess what researchers mean when they use this word.
To grasp Piaget’s explanation of how the shift from simple action to knowledge occurs, it is important to understand his concepts of scheme, assimilation, and accommodation. A scheme is a pattern of action that can be repeated. It is composed of affect, sensation, motor movements, and perception. Schemes begin with simple reflexes that gradually get more complex. For example, newborns have an initial ability to suck at their mother’s breast, and they quickly get better at this. This sucking scheme can be extended to explore other objects, such as an adult’s finger.
That is, other objects are assimilated to the sucking scheme. The infant applies her previous skills to engage in a new experience. But every new experience is different, and this results in accommodation, in the sense that sucking on the nipple of a bottle is different than sucking a mother’s breast – more vigorous sucking is required to obtain milk and some breastfed babies never manage to get used to this (i.e., they do not accommodate to it).
Assimilating objects to previous action schemes gives meaning or significance to new objects. The infant understands something in terms of what she can do with it. The processes of assimilation and accommodation are linked and are always involved in how children adapt to the world, gradually developing more complete knowledge of reality.
In assimilation, children understand their new experience in terms of past experience, expecting the world to behave as it has in the past. For example, when a baby sees an object that he has not yet learned is a toy rattle, he may assimilate it to his learned skill in grasping objects (i.e., his grasping scheme) based on his previous experience with objects that have a similar appearance, such as sticks. His expectations are based on his previous encounters with sticks. But because each new experience is always unique, the child accommodates to any differences and thus extends his knowledge in new ways. He then develops new anticipations of what may happen.
In this example, if a rattle that has been picked up makes a noise, the infant will learn to shake it but not perform the same action on sticks he has previously played with. Thus, new experiences change the child’s thinking fundamentally. He may then test whether grasping another new object produces a similar rattling sound.
This process also occurs during word learning. For example, a child might learn the word dog, but then assimilate other animals to this experience by referring to horses and squirrels with the same word. Later in development, students might learn about Piaget’s theory but assimilate it into their experience with social learning theories before, hopefully, recognizing the differences and accommodating to reach a deeper understanding.
Progress through Piaget’s stages of cognitive development occurs via a constant iterative process that results in a gradual construction of more complete knowledge of the world. Construction does not mean that this knowledge is made up, but that it is built on experience with reality.
Piaget’s worldview fits with current approaches in cognitive science based on embodiment and enaction (e.g., De Jaegher, Di Palolo, & Gallagher, 2010). This relational way of thinking is also consistent with many ways Indigenous people have of understanding the world and our relations with it (e.g., Ross, 2006). This perspective can be applied much more broadly beyond Piaget’s areas of interest to the development of communication and social understanding, and his own initial work on moral development can be extended.
Piaget described four stages of cognitive development: sensorimotor stage, preoperational stage, concrete operational stage, and formal operational stage.
In the sensorimotor stage, Piaget (1936/1963) described how infants transition from acting on the world to the beginning of mental activity. Development begins with a practical lived form of interaction centered on the child’s own body and movements that are initially involuntary. This stage builds on action in the development of thinking during the first 18 months. Infants are active and curious about new events and experiences. Babies begin interacting with action schemes like sucking, pushing, hitting, and grasping, to explore and manipulate the world they experience. From this perspective, newborns initially have no self-consciousness and no clear awareness of any effects they produce. By coordinating their actions on objects, often in social interactions, they develop a sense of themselves and how they relate to people and things. Piaget described six sub-stages within the sensorimotor stage.
Sub-stage 1: Reflex activity (birth to 1 month)
During the first month, babies’ interaction begins with sucking, rooting, grasping, touching, crying, and moving their arms and legs. Piaget described these actions as reflexes but not in the sense of involuntary bodily movements such as sneezing. These are actions newborns engage in and they also refine these skills.
Sub-stage 2: Primary circular reactions (1-4 months)
At this stage, a baby’s activity is focused on her own body (hence “primary”) and it is repetitive (hence “circular”). The baby tries to recreate experiences that initially happened by chance, such as sucking her thumb or grasping her foot. Also, two schemes, such as looking and grasping or reaching and sucking, may be combined into an action that the baby finds enjoyable. Piaget argued that this is not a passive process of forming associations. Instead, the baby actively explores and objects come to have significance for her.
Sub-stage 3: Secondary circular reactions (4-8 months)
The infant’s interaction at this stage changes from a focus on her own sensations to what is happening in the world. The baby starts to engage with objects and events (hence “secondary”) and repeats actions to reproduce their effects. For example, Piaget’s daughter repeatedly kicked while in her cot to make dolls that were hung above her move. She did not intend to make the dolls sway, she just enjoying that they did so, and she learned about the link between her kicking and the dolls moving.
At this stage of cognitive development, such learning is by accidental discovery. But it is focused on events in the world (e.g., seeing dolls move) rather than infants’ experience based on their own bodies (e.g., sucking or grasping). Infants’ attempts to grasp might accidently result in pushing and an object moving further away, and this could lead to interest in this unexpected outcome that the infant may explore. These examples illustrate infants’ interest and curiosity in actively exploring their world.
Sub-stage 4: Coordination of secondary schemes (8-12 months)
At this stage, babies begins to act intentionally, that is, to coordinate schemes to achieve a desired result. For example, an infant may move one object to reach another. This demonstrates the emergence of intentional activity because the baby is performing an action to achieve a desired result.
Sub-stage 5: Tertiary circular reactions (12-18 months)
At this stage, babies start active experimentation in the sense that they can apply a scheme to achieve a result, but if it does not work, they can try another scheme in their repertoire of action patterns.
Sub-stage 6: Invention of new means through mental combinations (over 18 months)
At this stage, toddlers start to find new ways of doing things on their own initiative instead of through trial and error. For example, in the case of Piaget’s daughter, instead of backing away awkwardly after bumping a toy pram into a wall, she paused for a moment and then walked around the pram to push it from the other side. It appeared that she was able to solve this problem by coordinating her actions implicitly or mentally without actually having to perform them first to grasp their consequence. That is, she could anticipate the outcome of her action even before performing the action. This indicates the end of the sensorimotor intelligence stage.
In addition to describing the six sub-stages, Piaget (1937/1971) also described how infants go through them in the process of developing concepts of the physical world, including objects, space, time, and causality. Most research has focused on infants’ developing understanding of objects. Counterintuitively, Piaget argued that infants do not start off with knowledge of objects. Instead, the knowledge of objects that we take for granted must be constructed gradually.
Piaget described how some knowledge of objects is already in place at 2 months, as indicated by infants’ expectations that someone who disappears from view would reappear. Then at sub-stage 3, infants can find an object if it is partially covered. At sub-stage 4, infants make an odd mistake called the A-not-B error. After they find an object a few times in location A, they continue looking for it in that location even when they see it placed in a new location, B. At sub-stage 5, infants no longer make this error and can find an object if they see it in the experimenter’s hand while it is being moved. Then at sub-stage 6, they can find the new location of the object even if the experimenter hides it in her hand.
In the preoperational stage, children begin to think about objects that are not right in front of them. Along with this advance in thinking, a limitation that is characteristic of this stage is intuitive thinking in which children focus on just one dimension at a time. Piaget devised a number of conservation tasks. For example, in the conservation of volume task, a child might figure out the amount of water in a glass by focusing only on the height of the liquid and not considering the glass’s width. This way of thinking leads to a number of errors due to misleading cues; the errors are overcome at the next stage.
According to Piaget, thinking begins in activity, but when actions are sufficiently mastered, they no longer have to be actually performed; they can be implicitly, or mentally, performed. Piaget referred to this process of mastering actions as interiorization and actions that are interiorized as operations.
Operations can be reversible in the sense that objects can be grouped together as well as separated, and liquid can be poured from a wide glass to a tall glass, and also back again so it reverts to its original state. That action can also be reversible in the sense that the dimension of the height of the liquid is simultaneously compensated for by the change in the width of the glass so the amount of liquid remains the same.
In the concrete operational stage, a child can now recognize this logical relation – that the volume of liquid does not change even though it might appear to do so – if the child focuses only on the one dimension (this is similar to what happens in pre-operational thinking when a child is fooled by a misleading cue). This is a logical conclusion about the principle of conservation, that is, even though there can be a misleading change in appearance, some underlying properties can remain the same.
For example, in the conservation of number task, two rows of objects (e.g., five coins) are presented to a child, who sees that there are the same number in each row, and then one row is spread out to make it longer. With pre-operational thinking, children are misled by this cue and tend to say that there are now more coins in the longer row. But with concrete operational thinking, they conclude that nothing has been added or taken away, and that logically, there must still be the same number of objects in each row.
Another type of concrete operational task involves transitivity problems (i.e., based on knowing the premises that A is greater than B and B is greater than C, being able to infer the conclusion that A is necessarily greater than C).
The formal operational stage is the final stage Piaget described. At this stage, children and adolescents can experiment by forming hypotheses and testing them systematically. This way of thinking involves abstract concepts, separating form from content (hence the name “formal operations”), and considering all possibilities. The formal operational stage is exemplified by hypothetico-deductive reasoning, in which all possibilities are considered and evaluated.
Piaget worked with his collaborator, Bärbel Inhelder, in assessing this thinking by presenting adolescents with problems based on physics and chemistry (Inhelder & Piaget, 1955/1958). For example, in the colorless liquid task, adolescents were presented with four colorless liquids and had to find out what combination of them resulted in a yellow liquid. Solving this problem requires systematically testing all possible combinations. Similarly, in the pendulum task, adolescents were asked to figure out whether the length of string, the weight of the pendulum, the height of dropping point, or the force of push determines a pendulum’s trajectory and movement. Again, solving requires systematically testing all possibilities.
Not all adolescents pass Piaget’s tests of formal operational thinking, either in western or non-western cultures (Piaget, 1972/2008). Piaget (1972/2008) considered various explanations for this, such as possible differences in the rate of intellectual development due to differences in stimulation, interests, or talents. But Piaget believed that typically developing adolescents were most likely to develop this form of thinking in the context of their own areas of expertise (e.g., gardening, baking, mechanics), areas in which they could systematically work through a problem in terms of the possible variables involved. Although formal operational thinking was the most advanced form of thinking Piaget and Inhelder studied, Piaget speculated about the possibility of other more advanced forms of thinking (Chapman, 1988b).
Although Piaget is known primarily for his research on children’s cognitive development, he devoted one of his early books to moral thinking (Piaget, 1932/1965). His perspective on moral development is not well appreciated, partly because it was assumed that Lawrence Kohlberg (e.g., 1976) continued and extended Piaget’s work. In fact, Piaget’s approach differed from Kohlberg’s in important ways – yet it still tends to be overlooked.
Piaget discussed the culturally constrained rules children learn from their parents (rules from the outside) that often result in little understanding of the reasons they should be followed (heteronomous morality). Piaget also discussed another form of morality that emerges in cooperative relationships based on mutual affection. Within relationships with equals, in particular, children want to interact with each other and thus have to work out ways of getting along, which leads to developing a practical morality. Morality is implicit in these ways of interacting. This involves making rules from the inside (autonomous morality): These rules are negotiated within cooperative relationships among equals in which children must explain themselves and listen to each other. This form of relationship is best suited to reaching mutual understanding and thus, to moral development.
To reach a verbal level of articulation, children still must go through a process of articulating the form of moral knowledge that is implicit in their interaction. Piaget referred to this as conscious realization of the morality that was already implicit in their interaction with each other (Carpendale, 2009; Piaget, 1932/1965). This insight regarding how the structure of relationships can facilitate the development of mutual understanding is also highly relevant for education.
As we have mentioned, any theory needs criticism for further development. And there certainly is such criticism of Piaget (e.g., see chapters in Müller, Carpendale, & Smith, 2009). Furthermore, Piaget suggested that he was his own greatest critic in constantly modifying his theory.
However, many of the criticisms of Piaget that are common in textbooks and online blogs are based on serious misinterpretations of Piaget’s work. As Piaget put it, “it is pretty catastrophic when I see how I am understood” (in Bringuier, 1980, p. 54). Next, we examine some of these criticisms to clarify the context and help deepen understanding of Piaget’s approach and theory (see also Chapman, 1988a; Lourenço & Machado, 1996).
One well-known challenge to Piaget comes from a group of researchers who claim that rather than having to develop knowledge, infants are born with innate knowledge of basic aspects of physics, biology, social understanding, and even morality (e.g., Spelke & Kinzler, 2007). Thus, infants do not need to develop knowledge of objects, as Piaget’s view of cognitive development suggests.
For example, by focusing on how long infants looked at various scenes, Renée Baillargeon (1987) claimed that compared to possible events, 4-month-olds looked longer at impossible events, such as when an object appeared to move through another object. She interpreted the differences in looking time as suggesting that infants were surprised by impossible events and thus must already understand that objects continue to exist.
Most textbooks stop at this point and conclude that Piaget was wrong about object permanence. However, there has been a great deal of debate over this matter, beginning with critical evaluation of the methods used to support such claims. In fact, we know that infants notice some difference between conditions if looking time varies, but not why. Looking times vary for many reasons (e.g., Carpendale, Lewis, & Müller, 2018).
Beyond the extensive debates about methodology, these claims of innate knowledge are examples of a representational theory of knowledge. They disregard Piaget’s starting point, which begins from a criticism of the assumption about how children learn about the world. These researchers have not solved the problem of knowledge that Piaget addressed. Instead, they ignore it. Thus, they assume but do not explain knowledge.
Furthermore, Piaget (1937/1971) said that infants had some knowledge of objects at 2 months, but he placed this early knowledge within a developmental framework in which infants gradually improve their understanding of objects toward a more complete understanding. In contrast, for the neonativists, such knowledge is viewed as dichotomous: A child either understands or does not understand that objects continue to exist.
Another common criticism is that Piaget’s tasks were too difficult for young children so he underestimated their abilities. Critics argued that changing the procedure to simplify the tasks would allow younger children to accomplish them, which would provide a more accurate assessment of their abilities. However, rather than providing a better assessment of their abilities, the simplified tasks can be solved with simpler forms of thinking, so they assess different abilities.
For example, the conservation of number task, which is usually done with five objects in each row, was simplified to two or three objects. Younger children could pass this task simply by seeing at a glance that each row still has the same number of objects, so they could pass without the logical understanding that Piaget wanted to assess, that the number of objects in a group does not change just by spreading them out to make the row look longer (Chapman, 1988a).
Another criticism is that children are inconsistent in the form of thinking they use. That is, a child may use concrete operational thinking on some but not all tasks (this is referred to as the problem of horizontal décalage). This evidence was thought to contradict Piaget’s stages of development. However, it does so only if Piaget had claimed that children are assumed to be in a particular stage and use only the form of intelligence of that stage.
In fact, Piaget described forms of thinking, and said children may use various forms to solve what to observers are closely related tasks. This evidence of inconsistency should be expected based on an understanding of his theory, which posits that children develop forms of thinking based on their experience interacting with objects. Whether children use concrete operational thinking depends on whether they gain sufficient experience with the particular materials in a specific task.
Piaget has also been criticized for underestimating the importance of social factors in development. He is sometimes contrasted with the Soviet psychologist Lev Vygotsky (1978), another influential figure in psychology, who emphasized the role of social interaction in development. But ironically, Vygotsky criticized Piaget’s early work for being too focused on social factors (Carpendale, Lewis, & Müller, 2018)! (For more information on Vygotsky, see next section.)
Piaget did recognize that social factors were important and necessary in development, but he believed that they alone do not fully explain development. He argued that what is also needed is the gradual back and forth process of trying out different strategies, which he described as equilibration. Also, it is not enough simply to make the obvious claim that social experience is important in development.
Piaget argued that it is necessary to go beyond this claim to consider the forms of social relations children experience. He emphasized cooperative interactions among equals, which allow for the development of mutual understanding. In these contexts, individuals need to listen to each other and explain their own position. This is in contrast to constraining social relationships based on one-sided respect in which children cannot ask questions and thus tend to lack understanding (Piaget, 1932/1965, 1977/1995).
A final criticism, perhaps the most misinformed one, is that Piaget’s theory is based on anecdotal evidence from his own children. It is hard to see where this claim came from because the number of experiments and participants in studies Piaget and his colleagues conducted has never been counted but is believed to be in the thousands.
Of Piaget’s 60 books, his three on infancy were based on observations of his own infants. But these are not just anecdotes; they draw on more than 1,200 pages of detailed notes recording observations made by Piaget and his wife, Valentine. The books have been described as “three of the most remarkable and original documents in psychology” (Russell, 1978, p. 92). In other books and scientific papers, particularly those he wrote with Inhelder, Piaget studied larger samples.
Piaget is often compared to Vygotsky. The Soviet psychologist was born the same year as Piaget (1896), but died at just 38 from tuberculosis, which he contracted after caring for his mother and younger brother. But even based on the few years he was active in the field, Vygotsky is influential and well known for his focus on the social origins of thinking. Vygotsky’s concern with the social dimension of development is often contrasted with Piaget’s, who was concerned with the individual cognitive dimensions of children’s development. Given this difference, some claim that their theories are incompatible.
However, although these two scholars differed, a more careful reading of their work suggests that they are quite compatible. Both began from the same approach examining action and interaction. When one of Vygotsky’s books was translated into English in 1962, the publisher asked Piaget to comment on it; he wrote that he fully agreed with Vygotsky’s view that forms of thinking have their origins in speech, and that thinking is first a social process before being mastered by individuals as a skill. Piaget’s fundamental point about knowledge developing from action within particular contexts links his approach to Vygotsky and to the importance of the cultural context of development.
We began this article with the suggestion that one reason Piaget remains relevant today is that he recognized the fundamental problem that must be solved in understanding the development of thinking. He suggested an approach to this problem beginning in activity that is congruent with current approaches in the cognitive sciences, such as embodied, enactive, and interactive approaches. Furthermore, this action-based, process-relational perspective can be extended beyond the topics that Piaget addressed to study the development of communication, social understanding, and moral development (see Carpendale & Lewis, 2021). This is consistent with sociocultural approaches inspired by Vygotsky and others.
Piaget’s approach is also consistent with contemporary thinking in biology that rejects a dichotomy between biology and social aspects of development by recognizing that they mutually create each other, and that it is more fruitful to think of development in terms of systems of interacting factors. Developmental systems theory in biology eschews a dichotomy between nature and nurture, or biology and social experience, and instead focuses on the process of development.
Infants cannot be born with knowledge, but instead are active agents with sensitivities that facilitate their engagement with parents and their physical embodiment functions to create their environment. For example, being born helpless creates a social environment because babies must be cared for, and their further neurological development occurs in this context.
This is only a small taste of the complex system of factors in which biology and social-cultural factors mutually create each other. Culture is a central part of this worldview. That is, individuals are created in families, communities, and societies, and they also maintain as well as change their cultures in a constant bidirectional process.
Piaget’s theory is consistent with current approaches that explain what it is to be human by beginning with action and interaction. Such approaches trace the emergence of thinking within the social, emotional, and communicative contexts of human experience.
For more by the authors of this article, see What makes us human? How minds develop in social interactions (Carpendale & Lewis, 2021).
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