Jean Piaget (August 9, 1896 – September 16, 1980) was a Swiss developmental psychologist, famous for working out a sequence of stages of cognitive development, and notable for his idea that children (and indeed adults) are continually generating theories about the external world (which are kept or dismissed depending on whether we see them working or not in practice).


Early life:

He was born in Neuchâtel in the French-speaking part of Switzerland. His father, Arthur, was a professor of medieval literature at the University of Neuchâtel. He was a precocious child and developed an interest in biology, particularly of mollusks, to the point of publishing a number of papers before he graduated from high school. His long scientific career began in 1907 at the age of eleven with the publication of a short paper on the albino sparrow. Over the next seven decades he wrote more than sixty books and several hundred articles.

He received a Ph.D. in natural science from the University of Neuchâtel and 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 can also be dated to this period.

He then moved from Switzerland to France, where he taught at the school for boys run by Alfred Binet, the developer of the Binet intelligence test, in Grange-aux-Belles. In 1921, he returned to Switzerland as director of the Rousseau Institute in Geneva.

In 1923, he married Valentine Châtenay, and they had three children, whom he studied from infancy.

The Stages of Cognitive Development:

Piaget became a professor of psychology at the University of Geneva from 1929 to 1975 and is best known for organizing cognitive development into a series of stages-- the levels of development corresponding to infancy, childhood, and adolescence. These four stages are labeled the Sensorimotor stage, which occurs from birth to age two, (children experience through their senses), the Preoperational stage, which occurs from ages two to seven (motor skills are acquired), the Concrete operational stage, which occurs from ages seven to eleven (children think logically about concrete events), and the Formal Operational stage, which occurs after age eleven (abstract reasoning is developed here). Advancement through these levels was explained through biology and culture along with a "third factor" called equilibration, working inter-dependently with the other two.

Piaget's view of the child's mind:

Piaget viewed children as little philosophers 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. For example children may not be able to conserve five checkers spread out and report that there are more checkers. If you reduce the number to three they could conserve numbers. By focusing on the fact they cannot conserve numbers for five items you would be slow to pick up that they can do it for lower numbers. Another surprise is if you tell them a magic bunny moved the objects they would conserve higher numbers. Most people miss that children are theoretical. But many children have imaginary playmates and love to play the game of let's pretend.


Piaget's theory of cognitive development has proved influential, notably on the work of Lev Vygotsky and of Lawrence Kohlberg. Among others, the philosopher and social theorist Jürgen Habermas has incorporated it into his work, most notably in The Theory of Communicative Action. Piaget also had a considerable impact 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. The philosopher Thomas Kuhn credited Piaget's work in helping him understanding the transition between modes of thought which characterised his theory of paradigm shifts.

Major works and achievements:

Single "best read" - Bringuier, J-C. (1980). Conversations with Jean Piaget. Chicago: University of Chicago Press.

Major Works:

  • Inhelder, B. and J. Piaget (1958). The Growth of Logical Thinking from Childhood to Adolescence. New York: Basic Books.
  • Piaget, J. (1962). Play, Dreams and Imitation in Childhood. New York: Norton.
  • Piaget, J. (1970). Structuralism. New York: Harper & Row.
  • Piaget, J. (1971). Biology and Knowledge. Chicago: University of Chicago Press.
  • Piaget, J. (1983). Piaget's theory. In P. Mussen (ed). Handbook of Child Psychology. 4th edition. Vol. 1. New York: Wiley.
  • Piaget, J. (1995). Sociological Studies. London: Routledge.
  • Piaget, J. (2000). Commentary on Vygotsky. New Ideas in Psychology, 18, 241-59.
  • Piaget, J. (2001). Studies in Reflecting Abstraction. Hove, UK: Psychology Press.


  • 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