Jean Piaget

Jean Piaget
Born	(1896-08-09)August 9, 1896 Neuchâtel, Switzerland
Died	September 16, 1980(1980-09-16) (aged 84)
Nationality	Swiss
Known for	Theory of cognitive development, Constructivism, Construtivist epistemology
Scientific career
Fields	Psychology

Jean Piaget [ʒɑ̃ pjaʒɛ] (August 9, 1896 – September 16, 1980) was a Swiss philosopher, natural scientist and developmental psychologist, well known for his work studying children, his theory of cognitive development and for his epistemological view called "genetic epistemology". He created in 1955 the International Centre for Genetic Epistemology in Geneva and directed it until 1980. According to Ernst von Glasersfeld, Jean Piaget is "the great pioneer of the constructivist theory of knowing".

Biography

Piaget was born in Neuchâtel in the French-speaking part of Switzerland. His father, Arthur Piaget, was a professor of medieval literature at the University of Neuchâtel. Piaget was a precocious child who developed an interest in biology and the natural world, particularly mollusks, and even published a number of papers before he graduated from high school. In fact, his long career of scientific research began when he was just ten, with the 1907 publication of a short paper on the albino sparrow. Over the course of his career, Piaget wrote more than sixty books and several hundred articles. Piaget received a Ph.D. in natural science from the University of Neuchâtel, and also studied briefly at the University of Zürich. During this time, he published two philosophical papers which showed the direction of his thinking at the time, but which he later dismissed as adolescent work. His interest in psychoanalysis, a strain of psychological thought burgeoning at that time, can also be dated to this period.

He then moved from Switzerland to Grange-aux-Belles, France, where he taught at the school for boys run by Alfred Binet, the developer of the Binet intelligence test. It was while he was helping to mark some instances of these intelligence tests that Piaget noticed that young children consistently gave wrong answers to certain questions. Piaget did not focus so much on the fact of the children's answers being wrong, but that young children kept making the same pattern of mistakes that older children and adults did not. This led him to the theory that young children's thought or cognitive processes are inherently different from those of adults. (Ultimately, he was to propose a global theory of developmental stages stating that individuals exhibit certain distinctive common patterns of cognition in each period in their development.) In 1921, Piaget returned to Switzerland as director of the Rousseau Institute in Geneva.

In 1923, he married Valentine Châtenay, one of his students; together, the couple had three children, whom Piaget studied from infancy. In 1929, Jean Piaget accepted the post of Director of the International Bureau of Education and remained the head of this international organization until 1968. Every year, he drafted his “Director’s Speeches” for the IBE Council and for the International Conference on Public Education in which he explicitly expressed his educational credo.

Scientific and philosophical development

The stages of cognitive development

Main article: Theory of cognitive development

Piaget served as professor of psychology at the University of Geneva from 1929 to 1975 and is best known for reorganizing cognitive development theory into a series of stages, expanding on earlier work from James Mark Baldwin: four levels of development corresponding roughly to (1) infancy, (2) pre-school, (3) childhood, and (4) adolescence. Each stage is characterized by a general cognitive structure that affects all of the child's thinking (a structuralist view influenced by philosopher Immanuel Kant). Each stage represents the child's understanding of reality during that period, and each but the last is an inadequate approximation of reality. Development from one stage to the next is thus caused by the accumulation of errors in the child's understanding of the environment; this accumulation eventually causes such a degree of cognitive disequilibrium that thought structures require reorganizing.

The four development stages are described in Piaget's theory as

1. Sensorimotor stage: from birth to age 2 years (children experience the world through movement and senses and learn object permanence)
2. Preoperational stage: from ages 2 to 7 (acquisition of motor skills)
3. Concrete operational stage: from ages 7 to 11 (children begin to think logically about concrete events)
4. Formal operational stage: after age 11 (development of abstract reasoning).

Piaget's view of the child's mind

Piaget viewed children as little philosophers, which he called tiny thought-sacks and scientists building their own individual theories of knowledge. Some people have used his ideas to focus on what children cannot do. Piaget, however, used their problem areas to help understand their cognitive growth and development.

The developmental process

Piaget provided no concise (or clear) description of the development process as a whole. Broadly speaking it consisted of a cycle:

• The child performs an action which has an effect on or organizes objects, and the child is able to note the characteristics of the action and its effects.
• Through repeated actions, perhaps with variations or in different contexts or on different kinds of objects, the child is able to differentiate and integrate its elements and effects. This is the process of reflecting abstraction (described in detail in Piaget 2001).
• At the same time, the child is able to identify the properties of objects by the way different kinds of action affect them. This is the process of empirical abstraction.
• By repeating this process across a wide range of objects and actions, the child establishes a new level of knowledge and insight. This is the process of forming a new cognitive stage. This dual process allows the child to construct new ways of dealing with objects and new knowledge about objects themselves.
• However, once the child has constructed these new kinds of knowledge, he or she starts to use them to create still more complex objects and to carry out still more complex actions. As a result, the child starts to recognize still more complex patterns and to construct still more complex objects. Thus a new stage begins, which will only be completed when all the child’s activity and experience have been re-organized on this still higher level.

This process is not wholly gradual, however. Once a new level of organization, knowledge and insight proves to be effective, it will quickly be generalized to other areas. As a result, transitions between stages tend to be rapid and radical, and the bulk of the time spent in a new stage consists of refining this new cognitive level. When the knowledge that has been gained at one stage of study and experience leads rapidly and radically to a new higher stage of insight, a "gestalt" is said to have occurred.

It is because this process takes this dialectical form, in which each new stage is created through the further differentiation, integration, and synthesis of new structures out of the old, that the sequence of cognitive stages are logically necessary rather than simply empirically correct. Each new stage emerges only because the child can take for granted the achievements of its predecessors, and yet there are still more sophisticated forms of knowledge and action that are capable of being developed.

Because it covers both how we gain knowledge about objects and our reflections on our own actions, Piaget’s model of development explains a number of features of human knowledge that had never previously been accounted for. For example, by showing how children progressively enrich their understanding of things by acting on and reflecting on the effects of their own previous knowledge, they are able to organize their knowledge in increasingly complex structures. Thus, once a young child can consistently and accurately recognize different kinds of animals, he or she then acquires the ability to organize the different kinds into higher groupings such as ‘birds’, ‘fish’, and so on. This is significant because they are now able to know things about a new animal simply on the basis of the fact that it is a bird – for example, that it will lay eggs.

At the same time, by reflecting on their own actions, the child develops an increasingly sophisticated awareness of the ‘rules’ that govern in various ways. For example, it is by this route that Piaget explains this child’s growing awareness of notions such as ‘right’, ‘valid’, ‘necessary’, ‘proper’, and so on. In other words, it is through the process of objectification, reflection and abstraction that the child constructs the principles on which action is not only effective or correct but also justified.

One of Piaget’s most famous studies focused purely on the discriminative abilities of children between the ages of two and a half years old, and four and a half years old. He began the study by taking children of different ages and placing two lines of M & M’s, one with the M & M’s in a line spread further apart, and one with the same number of M & M’s in a line placed more closely together. He found that, “Children between 2 years, 6 months old and 3 years, 2 months old correctly discriminate the relative number of objects in two rows; between 3 years, 2 months and 4 years, 6 months they indicate a longer row with fewer objects to have "more"; after 4 years, 6 months they again discriminate correctly” (Cognitive Capacity of Very Young Children, p. 141). Initially younger children were not studied, because if at four years old a child couldn’t conserve quantity, how could a child that is younger? The results show however that children that are younger than three years and two months have quantity conservation, but as they get older they lose this quality, and don’t recover it until four and a half years old. This attribute may be lost due to a temporary inability to solve because of an overdependence on perceptual strategies, which correlates more candy with a longer line of candy, or due to the inability for a four year old to reverse situations.

By the end of this experiment several results were found. First, younger children have a discriminative ability that shows the logical capacity for cognitive operations exists earlier than acknowledged. This study also reveals that young children can be equipped with certain qualities for cognitive operations, depending on how logical the structure of the task is. Research also shows that children develop explicit understanding at age 5 and as a result, the child will count the M & M’s to decide which has more. Finally the study found that overall quantity conservation is not a basic characteristic of man’s native inheritance.

Genetic epistemology

According to Jean Piaget, genetic epistemology "attempts to explain knowledge, and in particular scientific knowledge, on the basis of its history, its sociogenesis, and especially the psychological origins of the notions and operations upon which it is based".

Jean Piaget has become a reference for epistemology, and particularly for constructivist epistemology. According to Ernst von Glasersfeld, Jean Piaget is "the great pioneer of the constructivist theory of knowing".

Influence

Despite ceasing to be a fashionable psychologist, the magnitude of Piaget’s continuing influence can be measured by the global scale and activity of the Jean Piaget Society, which holds annual conferences and attracts very large numbers of participants. His theory of cognitive development has proved influential in many different areas:

• Developmental psychology
• Education
• Historical studies of thought and cognition
• Evolution of human intelligence
• Primatology
• Philosophy
• Artificial Intelligence (AI)
• Moral Education
• Morality in the child

Developmental psychology

Piaget is without doubt one of the most influential developmental psychologists, influencing not only the work of Lev Vygotsky and of Lawrence Kohlberg but whole generations of eminent academics. Although subjecting his ideas to massive scrutiny led to innumerable improvements and qualifications of his original model and the emergence of a plethora of neo-Piagetian and post-Piagetian variants, Piaget’s original model has proved to be remarkably robust (Lourenço and Machado 1996).

Stage One - Sensorimotor (birth to 1.5 years)
Stage Two - Preoperational (1.5 years to 7 years)
Stage Three - Concrete Operations (7 years to 11 years)
Stage Four - Formal Operations (11 years and onward)

Moral judgment stages were termed Heteronomy and Autonomy and were later further delineated by development psychologists.

Education

During the 1970s and 1980s, Piaget’s works also inspired the transformation of European and American education, including both theory and practice, leading to a more ‘child-centred’ approach. In Conversations with Jean Piaget, he says: "Education, for most people, means trying to lead the child to resemble the typical adult of his society . . . but for me and no one else, education means making creators. . . . You have to make inventors, innovators—not conformists," (Bringuier, 1980, p.132).

Historical studies of thought and cognition

Historical changes of thought have been modelled in Piagetian terms. Broadly speaking these models have mapped changes in morality, intellectual life and cognitive levels against historical changes (typically in the complexity of social systems). Robinson's History of Human Reason (2004) also suggests that history itself is the expression of our intelligence.

Notable examples include:

• Michael Barnes' study of the co-evolution of religious and scientific thinking (Barnes 2000)
• Peter Damerow's theory of prehistoric and archaic thought (Damerow 1995)
• Kieran Egan's stages of understanding
• James W. Fowler's stages of faith development
• Suzy Gablik's stages of art history (Gablik 1977)
• Christopher Hallpike’s studies of changes in cognition and moral judgment in pre-historical, archaic and classical periods (Hallpike 1979, 2004)
• Lawrence Kohlberg's stages of moral development
• Don Lepan's theory of the origins of modern thought and drama (LePan 1989)
• Charles Radding's theory of the medieval intellectual development (Radding 1985)
• R.J. Robinson's stages of history (Robinson 2004)
• E. Turiel. (1983), The development of social knowledge: Morality and convention. Cambridge University Press.
• E. Turiel. (2002). The culture of morality. Cambridge University Press.
• L.P. Nucci, (2001, Education in the moral domain. Cambridge University Press.

Evolution of human intelligence

The origins of human intelligence have also been studied in Piagetian terms. Wynn (1979, 1981) analysed Acheulian and Oldowan tools in terms of the insight into spatial relationships required to create each kind. On a more general level, Robinson’s Birth of Reason (2005) suggests a large-scale model for the emergence of a Piagetian intelligence.

Moral Reasoning and Moral Judgment

Piaget's theory of morality was radical in 1932, when his book, The Moral Judgment of the Child, was published, due to his use of philosophical criteria to define morality (as universalizable, generalizable, and obligatory), and his rejection of equating cultural norms and moral norms. Piaget, drawing on Kantian theory, proposed that morality developed out of peer interaction, and that it was autonomous from authority mandates. Peers, not parents, were a key source of moral concepts, such as equality, reciprocity, and justice.

Primatology

Piaget’s models of cognition have also been applied outside the human sphere, and there is a thriving community of primatologists assessing the development and abilities of primates in terms of Piaget’s model. Notable names include Sue Taylor Parker and Francesco Antinucci. A summary of the very extensive literature can be found in Parker and McKinney (1999). Neo-Piagetian stages have been describe by Commons and Miller (2004)

Evolutionary Psychology

Neo-Piagetian stages have been applied to the maximum stage attained by various animals. For example spiders attain the circular sensory motor stage, coordinating actions and perceptions. Pigeons attain the sensory motor stage, forming concepts.

Philosophy

Some have taken account of Piaget's work. For example, the philosopher and social theorist Jürgen Habermas has incorporated Piaget into his work, most notably in The Theory of Communicative Action. The philosopher Thomas Kuhn credited Piaget's work in helping him understand the transition between modes of thought which characterized his theory of paradigm shifts. Shortly before his death (October 1975), Piaget was involved in a debate about the relationships between innate and acquired features of language, at the Centre Royaumont pour une Science de l'Homme, where he discussed his point of view with the linguist Noam Chomsky as well as Hilary Putnam and Stephen Toulmin.

AI

Piaget also had a considerable effect in the field of computer science and artificial intelligence. Seymour Papert used Piaget's work while developing the Logo programming language. Alan Kay used Piaget's theories as the basis for the Dynabook programming system concept, which was first discussed within the confines of the Xerox Palo Alto Research Center, or Xerox PARC. These discussions led to the development of the Alto prototype, which explored for the first time all the elements of the graphical user interface (GUI), and influenced the creation of user interfaces in the 1980's and beyond.

Major works and achievements

Major works

• Piaget, J. (1950). Introduction à l’Épistémologie Génétique. Paris: Presses Universitaires de France.
• Piaget, J. (1961). La psychologie de l'intelligence. Paris: Armand Colin (1961, 1967, 1991). Online version
• Piaget, J. (1967). Logique et Connaissance scientifique, Encyclopédie de la Pléiade.

• Inhelder, B. and J. Piaget (1958). The Growth of Logical Thinking from Childhood to Adolescence. New York: Basic Books.
• Inhelder, B. and Piaget, J. (1964). The Early Growth of Logic in the Child: Classification and Seriation. London: Routledge and Kegan Paul.
• Piaget, J. (1928). The Child's Conception of the World. London: Routledge and Kegan Paul.
• Piaget, J. (1932). The Moral Judgment of the Child. London: Kegan Paul, Trench, Trubner and Co.
• Piaget, J. (1952). The Child's Conception of Number. London: Routledge and Kegan Paul.
• Piaget, J. (1953). The Origins of Intelligence in Children. London: Routledge and Kegan Paul.
• Piaget, J. (1955). The Child's Construction of Reality. London: Routledge and Kegan Paul.
• Piaget, J. (1971). Biology and Knowledge. Chicago: University of Chicago Press.
• Piaget, J. (1995). Sociological Studies. London: Routledge.
• Piaget, J. (2001). Studies in Reflecting Abstraction. Hove, UK: Psychology Press.

Other works

• Beth, E.W., and Piaget, J. (1966). Mathematical Epistemology and Psychology. Dordrecht: D. Reidel.
• Piaget, J. (1942). Les trois structures fondamentales de la vie psychique: rythme, régulation et groupement. Rev. Suisse de Psychologie Appliquée, 1/2 9–21.
• Piaget, J. (1948). Où va l’éducation? UNESCO.
• Piaget, J. (1951). Psychology of Intelligence. London: Routledge and Kegan Paul

• Piaget, J. (1953). Logic and Psychology. Manchester: Manchester University Press.

• Piaget, J. (1962). Play, Dreams and Imitation in Childhood. New York: Norton.
• Piaget, J. (1966). Nécessité et signification des recherches comparatives en psychologie génétique. Journal International de Psychologie, 1 (1): 3-13.
• Piaget, J. (1970). Structuralism. New York: Harper & Row.
• Piaget, J. (1972). Psychology and Epistemology: Towards a Theory of Knowledge. Harmondsworth: Penguin.
• Piaget, J. (1972). Insights and Illusions of Philosophy. London: Routledge and Kegan Paul.
• Piaget, J. (1974). Experiments in Contradiction. Chicago: University of Chicago Press.
• Piaget, J. (1974). The Place of the Sciences of Man in the System of Sciences. New York: Harper and Row, Publishers.
• Piaget, J. (1975). The Origin of the Idea of Chance in Children. London: Routledge and Kegan Paul.
• Piaget, J. (1977). The Grasp of Consciousness. London: Routledge and Kegan Paul.
• Piaget, J. (1978). Success and Understanding. London: Routledge and Kegan Paul.
• Piaget, J. (1979). Behaviour and Evolution. London: Routledge and Kegan Paul.
• Piaget, J. (1980). Adaptation and Intelligence. London: University of Chicago Press.
• Piaget, J. (1980). Les Formes Élémentaires de la Dialectique. Paris, Editions Gallimard.
• Piaget, J. (1981). Intelligence and Affectivity. Their Relationship during Child Development. Palo Alto: Annual Reviews.
• Piaget, J. (1983). Piaget's theory. In P. Mussen (ed.). Handbook of Child Psychology. 4th edition. Vol. 1. New York: Wiley.
• Piaget, J. (1985). The Equilibration of Cognitive Structures: The Central Problem of Intellectual Development. Chicago: University of Chicago Press.
• Piaget, J. (1987). Possibility and Necessity. 2 vols. Minneapolis: University of Minnesota Press.
• Piaget, J. (2000). Commentary on Vygotsky. New Ideas in Psychology, 18, 241-59.
• Piaget, J., and Garcia, R. (1989). Psychogenesis and the History of Science. New York: Columbia University Press.
• Piaget, J., and Garcia, R. (1991). Towards a Logic of Meanings. Hillsdale, N.J.: Lawrence Erlbaum Associates.
• Piaget, J., and Inhelder, B. (1962). The Psychology of the Child. New York:Basic Books
• Piaget, J., and Inhelder, B. (1967). The Child’s Conception of Space. New York: W.W. Norton.

Appointments

• 1921-25 Research Director, Institut Jean-Jacques Rousseau, Geneva
• 1925-29 Professor of Psychology, Sociology and the Philosophy of Science, University of Neuchatel
• 1929-39 Professor of the History of Scientific Thought, University of Geneva
• 1929-67 Director, International Bureau of Education, Geneva
• 1932-71 Director, Institute of Educational Sciences, University of Geneva
• 1938-51 Professor of Experimental Psychology and Sociology, University of Lausanne
• 1939-51 Professor of Sociology, University of Geneva
• 1940-71 Professor of Experimental Psychology, University of Geneva
• 1952-64 Professor of Genetic Psychology, Sorbonne, Paris
• 1955-80 Director, International Centre for Genetic Epistemology, Geneva
• 1971-80 Emeritus Professor, University of Geneva

Piagetian and post-Piagetian stage theories

• Michael Barnes' historical stages of religious and scientific thinking (Barnes 2000)
• Peter Damerow's theory of prehistoric and archaic thought (Damerow 1995)
• Kieran Egan's stages of understanding
• James W. Fowler's stages of faith development
• Zendra Moore's stages of art history (Gablik 1977)
• Christopher Hallpike's historical stages of cognitive moral understanding (Hallpike 1979, 2004)
• Lawrence Kohlberg's stages of moral development
• Don Lepan's theory of the origins of modern thought and drama (LePan 1989)
• Charles Radding's theory of the medieval intellectual development (Radding 1985)
• R.J. Robinson's stages of history (Robinson 2004)
• Robert Kegan's constructive-developmental theory (Kegan 1982)
• Allen Ivey's developmental counseling and therapy (DCT) (Ivey 1986)
• Keith S. Lockwood's constructivist practice with children who are deaf or hard of hearing (Lockwood 2006)

Quotations

• "Intelligence is what you use when you don't know what to do."
• "Intelligence organizes the world by organizing itself."

See also

• Constructivist epistemology
• Developmental psychology
  • Developmental stage
• Inquiry-based science
• Erik Erikson, Erikson's stages of psychosocial development
• Lawrence Kohlberg, Kohlberg's stages of moral development

References

• Aqueci, F. (2003). Ordine e Trasformazione. Morale, Mente, Discorso in Jean Piaget. Acireale-Roma: Bonanno
• Amann-Gainotti M. and Ducret J.-J. (1992). Jean Piaget, disciple of Pierre Janet: influence of behavior psychology and relations with psychoanalysis. Information psychiatrique vol. 68, no6, pp. 598-606
• Barnes, M.H. (2000). Stages of Thought. The Co-Evolution of Religious Thought and Science. Oxford University Press: New York.
• Beilin, H. (1992). Piaget's enduring contribution to developmental psychology. Developmental Psychology, 28, 191-204.
• Bringuier, J.-C. (1980). Conversations with Piaget. Chicago: Chicago University Press.
• Chapman, M. (1988). Constructive Evolution: Origins and Development of Piaget's Thought. Cambridge: Cambridge University Press.
• Damerow, P. (1995). Prehistory and cognitive development. Invited Lecture to the Twenty-Fifth Annual Symposium of the Jean Piaget Society, Berkeley, June 1–3, 1995.
• Duveen, G. & Psaltis, C. (in press). The constructive role of asymmetries in social interaction.In U. Mueller, J.Carpendale, N. Budwig & B. Sokol : Social Life and Social Knowledge: Toward a Process Account of Development. Mahwah, NJ: Lawrence Erlbaum
• Flavell, J. (1967). The Developmental Psychology of Jean Piaget. New York: D. Van Nostrand Company.
• Fowler, James W. (1981). Stages of Faith, Harper & Row ISBN 0-06-062866-9
• Gablik, S. (1977). Progress in Art. Rizzoli: New York.
• Gattico, E. (2001). Jean Piaget. Milano: Bruno Mondadori
• Hallpike, C.R. (1979). The Foundations of Primitive Thought. Oxford: Oxford University Press.
• Hallpike, C.R. (2004). The Evolution of Moral Understanding. Prometheus Research Group: www.prometheus.org.uk.
• Kesselring, Th. (1999). Jean Piaget. München: Beck
• Kitchener, R. (1986). Piaget's Theory of Knowledge. New Haven: Yale University Press.
• LePan, D. (1989). The Cognitive Revolution in Western Culture. Vol. 1: The Birth of Expectation. Basingstoke: Macmillan.
• Lourenço, O. and Machado, A. (1996). In defense of Piaget’s theory: A reply to ten common criticisms. Psychological Review, 103, 1: 143–164.
• Psaltis, C., & Duveen, G. (2006). Social relations and cognitive development: The influence of conversation type and representations of gender. European Journal of Social Psychology, 36, 407-430
• Psaltis, C. & Duveen, G. (2007). Conversation types and conservation: Forms of recognition and cognitive development. British Journal of Developmental Psychology, 25, 79-102.
• Parker, S.T. and McKinney, M.L. (1999). Origins of Intelligence: The Evolution of Cognitive Development in Monkeys, Apes and Humans. Baltimore: Johns Hopkins University Press.
• Radding, C.M. (1985). A World Made by Men. Cognition and Society, 400–1200. Chapel Hill: University of North Carolina Press.
• Robinson, R.J. (2004). The History of Human Reason. Prometheus Research Group: www.prometheus.org.uk.
• Robinson, R.J. (2005). The Birth of Reason. Prometheus Research Group: www.prometheus.org.uk.
• Smith, L. (1992). Jean Piaget: Critical Assessments. 4 Vols. London: Routledge.
• Smith, L. (1993). Necessary Knowledge: Piagetian Perspectives on Constructivism. Hove, Lawrence Erlbaum.
• Smith, L. (1996). Critical Readings on Piaget. London: Routledge.
• Vonèche, J.J. (1985). Genetic epistemology: Piaget's theory. International Encyclopedia of Education, Vol. 4. Oxford: Pergamon.
• Smith, L. (2001). "Jean Piaget". In J. A. Palmer (ed.) 50 Modern Thinkers on Education: from Piaget to the Present. London: Routledge
• Vidal, F. (1994). Piaget before Piaget. Cambridge, MA: Harvard University Press.
• Wynn, T. (1979). The intelligence of later Acheulean hominids. Man (ns), 14: 371–391.
• Wynn, T. (1981). The intelligence of Oldowan hominids. Journal of Human Evolution, 10: 529–541.
• Ivey, A. (1986). Developmental therapy. San Francisco: Jossey-Bass.

External links

• Jean Piaget Society, society for the study of knowledge and development.
• The Jean Piaget Archives, with full bibliography.
• Jean Piaget's Genetic Epistemology: Appreciation and Critique by Robert Campbell (2002), extensive summary of work and biography.
• The Construction of Reality in the Child by Jean Piaget(1955)
• Piaget's role in the International Bureau of Education and the International Conference on Education
• Genetic Epistemology by Jean Piaget(1968)
• Comments on Vygotskyby Jean Piaget(1962)
• Piaget's Development Theory
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