History of Psychology Course

Paul F. Ballantyne, Ph.D.

From: Baron, R.; Earhard, B.; & Ozier, M. (1995). Psychology (Canadian Edition, pp. 326-329). Scarborough, ON: Allyn & Bacon.

Piaget's Theory: An Overview

Piaget's stage theory of cognitive development is a stage theory. It proposes that, in the development of our thinking, we move through an orderly and predictable series of steps. Stage theories have been applied to many other aspects of human behavior as well -notably to the development of personality ... However, many psychologists currently question the ideas that (1) all human beings move through set stages; (2) they do so at certain ages; and (3) the order of this progress is unchanging (Flavell, 1985). Indeed, there is so much variability among people that there is some question about how valid stage theories are.

What is it that, in Piaget's view, underlies cognitive development? What keeps us advancing from stage to stage, to more and more complex thinking? According to Piaget, from birth on, as we interact with the world, we construct mental representations of it (Olson, 1993). This ongoing process is called adaptation. We adapt our past mental representations of the world to include our current experience. Adaptation occurs in two ways. First, there is assimilation, which occurs when we incorporate new information into existing mental structures. For example, when infants encounter a new kind of toy -perhaps a jack-in-the-box- they try to treat it as they have other toys -perhaps shaking it like a rattle or banging it like a drum. When these old strategies do not work, accommodation must be made. Since existing structures cannot handle the new information being received, a new way to deal with the environment (in this case, turning a handle) must be devised.

For Piaget, it is the tension between assimilation and accommodation that results in adaptation, cognitive development, and ever more complex understanding of the world around us.

Now let's turn to the details of Piaget's stages of cognitive development.

THE SENSORIMOTOR STAGE: LEARNING TO REPRESENT THE WORLD INTERNALLY The first of Piaget's stages lasts from birth until between 18 and 24 months. During this period -the sensorimotor stage- infants gradually learn there is a relationship between their actions and the external world. They discover that when they manipulate objects, there are consequences. In short, they acquire a basic idea about cause and effect. For example, they learn to perform movements that affect the physical world: pulling, striking, swinging, and rubbing. They learn to reach for objects while looking at them, and to open their mouths differently for a nipple or a spoon.

Throughout the sensorimotor period, infants know the world through motor activities ... and sensory impressions ... They have not yet learned to use mental representations or images to represent objects or events. This results in some interesting contradictions. For example, if an object is hidden from view, four-month-olds will not attempt to search for it. Generally for these infants, it is "out of sight, out of mind." By eight or nine months of age, however, the situation changes. Infants of this age will search for the hidden object. They have developed object permanence -the understanding that objects continue to exist even after they are no longer seen. In contrast, object permanence in kittens appears much more rapidly (Dumas & Dore, 1989). Delays in the appearance of object permanence have been studied in special populations, such as children with defective limbs (McDonnell, 1988) and children who are visually impaired from birth (Bigelow, 1990). In blind children there are similarities in the development of object permanence, but also differences because of their special reliance on touch perception (Bigelow, 1986). [p. 327]

THE PREOPERATIONAL STAGE: GROWTH OF SYMBOLIC ACTIVITY Some time between the ages of 18 and 24 months, Piaget contends, children develop the ability to form mental representations of objects and events. At the same time, language develops, as does the beginning of thinking in words. These developments mark the end of the sensorimotor period and the start of the preoperational stage.

During this stage, which lasts until about age seven, children are capable of many feats they could not perform earlier. For example, they begin make-believe play ..., enacting familiar routines, such as pretending to eat or go to sleep. In order to create play, they must represent these activities mentally and translate them into overt actions.

While the thinking of preoperational children is more advanced, Piaget emphasizes that children at this stage of cognitive development are still quite immature in several important respects. First, they are limited by egocentrism; that is, they have difficulty understanding that other people may perceive the world differently (Piaget, 1975). Consider the following demonstration (Flavell, 1973): Two-year-olds are shown that a card has a picture of a dog on one side and a cat on the other. The card is then placed between the child and the experimenter so that each can see only one side. Now the experimenter asks the child two questions: What do you see? and What do I see? Because of egocentric thought, many children say that the experimenter sees the same picture as they do. As we'll see, however, the results obtained in such demonstrations depend on which questions are asked. Under some conditions, even two-year-olds are capable of recognizing that what other people see may be quite different (Lempers, Flavell, & Flavell, 1977).

Children in the preoperational stage lack understanding of relational terms, such as darker, larger, and harder. Further, they lack seriation -the ability to arrange objects in order from large to small, for example. Finally, and perhaps most important, they lack conservation -the understanding that the physical attributes of an object remain unchanged even though their appearance has changes. For example, say a four-year-old is shown two identical lumps of clay. One lump is then flattened into a large pancake as the child watches. Asked whether the two lumps still contain the same amount of clay, the child may answer no.... Similar findings result when children of this age watch water from a tall, thin container being poured into a shorter but wider one. When asked whether a second tall container and the new shorter one contain the same amount of water, at this stage children again answer no. [p. 328]

THE STAGE OF CONCRETE OPERATIONS: THE EMERGENCE OF LOGICAL THOUGHT By the time they are six or seven, most children have gained an understanding of conservation. According to Piaget, this marks the beginning of the third major stage of cognitive development -the stage of concrete operations.

During this stage, which lasts until about the age of eleven, many important cognitive skills emerge. Children gain an understanding of [concrete] relational terms and seriation. They come to understand reversibility -the fact that many physical changes can be undone by reversing the original action. They also begin to make greater use of categories in describing and thinking about the physical world. Thus, if asked to sort various objects, four-year-olds will often do so in terms of color or size. Older children place objects in more complex categories, those which take account of several features at once. For example, they will categorize bananas, oranges, apples, and pineapples as fruits, despite major variations in color, shape, and size.

Finally, when children reach the stage of concrete operations, they begin to engage in [contextualized] logical thought. If asked, "Why did you and your mother go to the store?" they will reply, "Because my mother needed some milk." Younger children, in contrast, might say, "Because afterwards, we came home."

THE STAGE OF FORMAL OPERATIONS: DEALING WITH ABSTRACTION AS WELL AS [CONCRETE] REALITY At about the age of twelve, Piaget suggests, most children enter the final stage of cognitive development -the stage of formal operations. During this time, major features of adult thought appear. This may have to do with changes in frontal lobe function by this age (Segalowitz et al., 1992).

While children in the stage of concrete operations can think logically, they do so about concrete events and objects. In contrast, at the stage of formal operations, they can think abstractly. That is, they can deal not only with the real, or concrete, but also with possibilities -with potential events or relationships that do not exist [in their immediate context or past experience] but can be imagined. As a result, they become able to doubt, as studies by Bayers and Chandler at the University of Calgary have shown ...

During this final stage of cognitive development, children become capable of hypothetico-deductive reasoning. When faced with a problem, they can formulate a general theory that includes all possible factors. From this, they reason deductively to formulate specific hypotheses, which can then be tested by examining existing evidence (or acquiring new evidence). Individuals who reach the stage of formal operations use propositional reasoning. They assess the logical validity of verbal statements, even when those refer to possible events rather than to real events in the world.

While thinking of young adolescents matches (approximately) that of adults, Piaget believed that it still falls short. Thus, young adolescents, often use their new reasoning to construct sweeping theories of religion, ethics, or politics. While this reasoning may be logical, the theories are often naive, because the individuals who construct them do not consider adequately the consequences in real life.

One final point: While people who have reached the stage of formal operations are capable of engaging in hypothetico-deductive reasoning, propositional thought, and other advanced forms of thinking, there is no guarantee that they will actually do so. On the contrary, even adults slip back (Kuhn, 1989). Having the capacity for logical thought, then, does not ensure that it will actually occur.

Piaget's Theory: A Modern Assessment

All theories in psychology are subject to rigorous scientific scrutiny. But theories like Piaget's need very careful assessment because of their sweeping assertions. This being the case, it is not surprising to learn that Piaget's ideas [p. 329] have been the focus of a large number of subsequent investigations (Flavell, 1982). The results suggest that his theory, although insightful in many respects, does not provide a completely accurate account of cognitive development. Piaget's theory is incorrect, or at least requires major revision, with respect to these three issues: (1) the ages at which infants and preschoolers reach the milestones of cognitive development; (2) how distinct the stages of cognitive development are; and (3) the role of language and the importance of social interaction with caregivers in cognitive growth.

THE CASE OF THE COMPETENT PRESCHOOLER There is reason to believe that Piaget seriously underestimated the cognitive abilities of infants and young children. For example, infants show a basic grasp of object permanence even at four-and-a-half months (Baillargeon, 1987). Similarly, children as young as three have some understanding of the concept of conservation -the fact that certain physical attributes of an object can remain unchanged even though the outward appearance of the object is altered (Cuneo, 1980) -and of symbolic thought (Bialystok, 1992).

DISCRETE STAGES IN COGNITIVE DEVELOPMENT: MYTH OR REALITY? Piaget proposed that cognitive development happens in discrete steps and that these are discontinuous: children must complete one before entering the next. Most research findings, however, indicate that cognitive changes occur in a gradual manner. Rarely does an ability that is entirely absent at one age make a sudden appearance. Developmental psychologists disagree about this basic aspect of Piaget's thought.

LANGUAGE AND THE SOCIAL CONTEXT OF COGNITIVE DEVELOPMENT Young children often talk to themselves as they go about their daily activities, giving themselves instructions about what to do next. Piaget called this egocentric speech and suggested that it was a sign of cognitive immaturity -an inability to take account of the perspective of others. The Soviet psychologist Vygotsky (1987) objected strongly, contending that private speech is not egocentric; on the contrary, he thought that it occurs when young children encounter obstacles and difficulties, and that it represents their efforts at self-guidance. Vygotsky felt that this early use of language helps young children reflect on their own behavior, and that it plays a key role in cognitive development. The results of many studies have confirmed his views (e.g., Bivens & Berk, 1990).

There is also support for Vygotsky's contention that social communication with caregivers plays a key role in cognitive growth. He taught that cognitive development is enhanced by parent-child interactions, and again, research findings offer support for this idea. For example, children whose parents encourage them to use more private speech are more successful when working alone (Behrend, Rosengren, & Perlmutter, 1992). Of course, verbal communication between adult and child is not the only means through which children's thinking develops. However, it does seem to play a more important role than Piaget believed, so Vygotsky's views pose another serious challenge to Piaget's theory.

In sum, there is now general agreement among developmental psychologists that Piaget's theory is not completely accurate (MacNamara & Austin, 1993; Siegel, 1993). It gives too little credit to the cognitive abilities of infants and young children, it overemphasizes the importance of discrete stages, and it underestimates the role of private speech and social interaction with caregivers. Despite these problems, however, the impact of Piaget's theory remains profound. It has forever altered our ideas about how children think and reason and has served as a framework for much research on cognitive development.


Baillargeon, R. (1987). Object permanence in 3 1/2 - 4 1/2 month old infants. Dev. Psyc., 23, 655-664.

Behrend, D., Rosengren, K., & Perlmutter, M. (1992). The relation between private speech and parental interactive style. In R.M. Diaz & L.E. Berk (Eds.). Private Speech: From social interaction to self-regulation (pp. 85-100). Hillsdale, NJ: Erlbaum.

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Bigelow, A. (1990). Relationship between the development of language and thought in young blind children. J. of Visual Impairment and Blindness, 84, 414-419.

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MacNamara, J. & Austin, G. (1993). Trick or Treat: Children's understanding of surprise Cognitive Dev., 8, 27-46.

McDonnell, P. (1988). Developmental response to limb deficiency and limb replacement. Canadian J. of Psyc., 42, 120-143.

Piaget, J. (1975). The child's conception of the world. Totowa, NJ: Littlefield, Adams. (Originally published 1932).

Segalowitz, S., Unsal, A, & Dywan, J. (1992). Cleverness and wisdom in 12-year-olds: Electrophysiological evidence for late maturation of the frontal lobs. Developmental Neuropsychology, 8, 279-298.

Siegel, L. (1993). Amazing new discovery: Piaget was wrong. Canadian Psyc., 34, 239-245.

Vygotsky, L.S. (1987). Thinking and speech. In R.W. Rieber, A. Carton (Eds.). The Collected Works of Vygotsky, Vol. 1, 37-285.

Paul F. Ballantyne, Ph.D. Posted [December, 2006]