A baby playing with his toes.
In the sensorimotor stage of infant development, the infant relates sounds or movements to a specific object or person.
In the sensorimotor stage, the infant orients himself or herself to objects in the world by consistent physical (motor) movements in response to those sensory stimuli that represent the same object (for example, the sight of a face, the sound of footsteps, or a voice all represent “mother”). The relationship between motor responses and reappearing objects becomes progressively more complex and varied in the normal course of development. First, reflexes such as sucking become more efficient; then sequences of learned actions that bring pleasure are repeated (circular reactions). These learned reactions are directed first toward the infant’s own body (thumb sucking), then toward objects in the environment (the infant’s stuffed toy).
Babies seem to lack an awareness that objects continue to exist when they are outside the range of their senses. When the familiar toy of an infant is hidden, the infant does not search for it; it is as if it has disappeared from reality. As the sensorimotor infant matures, the infant becomes convinced of the continuing existence of objects that disappear in less obvious ways for longer intervals of time. By 18 months of age, most toddlers have achieved such a conviction of continuing existence, or object permanence.
In the preoperational stage, the preschool child begins to represent these permanent objects by internal processes or mental representations. Now the development of mental representations of useful objects proceeds at an astounding pace. In symbolic play, blocks may represent cars and trains. Capable of deferred imitation, the child may pretend to be a cowboy according to his memory image of a motion-picture cowboy. The most important of all representations are the hundreds of new words the child learns to speak.
As one might infer from the word “preoperational,” this period, lasting from about age 2 through ages 6 or 7, is transitional. Preschool children still lack the attention, memory capacity, and mental flexibility to employ their increasing supply of symbolic representations in logical reasoning (operations). It is as if the child remains so focused on the individual frames of a motion picture that the child fails to comprehend the underlying plot. Piaget calls this narrow focusing on a single object or salient dimension centration. The child may say, for example, that a quart of milk the child has just seen transferred into two pint containers is now “less milk” because the child focuses on the smaller size of the new containers. Fido is seen as a dog, not as an animal or a mammal. Children uncritically assume that other people, regardless of their situation, share their own tastes and perspectives. A 2-year-old closes his eyes and says, “Now you don’t see me, Daddy.” Piaget calls this egocentrism.
Concrete Operations Stage
The concrete operations stage begins at age 6 or 7, when the school-age child becomes capable of keeping in mind and logically manipulating several concrete objects at the same time. The child is no longer the prisoner of the momentary appearance of things. In no case is the change more evident than in the sort of problem in which a number of objects (such as 12 black checkers) are spread out into four groups of three. While the 4-year-old, preoperational child would be likely to say that now there are more checkers because they take up a larger area, to the 8-year-old it is obvious that this transformation could easily be reversed by regrouping the checkers. Piaget describes the capacity to visualize the reversibility of such transformations as “conservation.” This understanding is fundamental to the comprehension of simple arithmetical manipulations. It is also fundamental to a second operational skill: categorization. To the concrete-operational child, it seems obvious that while Rover the dog can for other purposes be classified as a household pet, an animal, or a living organism, he will still be a “dog” and still be “Rover.” A related skill is seriation: keeping in mind that an entire series of objects can be arranged along a single dimension, such as size (from smallest to largest). The child now is also capable of role-taking, of understanding the different perspective of a parent or teacher. No longer egocentric (the assumption that everyone shares one’s own perspective and the cognitive inability to understand the different perspective of another), the child becomes able to see himself as others see him and to temper the harshness of absolute rules with a comprehension of the viewpoints of others.
Formal Operations Stage
The formal operations stage begins in early adolescence. In childhood, logical operations are concrete ones, limited to objects that can be visualized, touched, or directly experienced. The advance of the early adolescent into formal operational thinking involves the capacity to deal with possibilities that are purely speculative. This permits coping with new classes of problems: those involving relationships that are purely abstract or hypothetical, or that involve the higher-level analysis of a problem by the systematic consideration of every logical (sometimes fanciful) possibility. The logical adequacy of an argument can be examined apart from the truth or falsity of its conclusions.
Concepts such as “forces,” “infinity,” or “justice,” nowhere directly experienced, can now be comprehended. Formal operational thought permits the midadolescent or adult to hold abstract ideals and to initiate scientific investigations.
Illustrating Stage Development
Piaget was particularly clever in the invention of problems that illustrate the underlying premises of the child’s thought. The crucial capability that signals the end of the sensorimotor period is object permanence, the child’s conviction of the continuing existence of objects that are outside the range of one’s senses. Piaget established the gradual emergence of object permanence by hiding from the child familiar toys for progressively longer periods of time, with the act of hiding progressively less obvious to the child. Full object permanence is not considered achieved until the child will search for a familiar missing object even when the child could not have observed its being hidden.
A young child playing peekaboo with a toddler.
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One reason babies love the peekaboo game is because they have not developed object permanence yet. Until they go through this stage, they believe objects to disappear when they leave their sight.
The fundamental test of concrete operational thought is conservation. In a typical conservation task, the child is shown two identical balls of putty. The child generally affirms their obvious equivalence. Then one of the balls of putty is reworked into an elongated, wormlike shape while the child watches. The child is again asked about their relative size. Younger children are likely to say that the wormlike shape is smaller, but the child who has attained conservation of mass will state that the size must still be the same. Inquiries concerning whether the weights of the differently shaped material (conservation of weight) are the same and whether they would displace the same amount of water (conservation of volume) are more difficult questions, generally not answerable until the child is older.
Standardized Tests to Measure Piaget’s Concepts
Since Piaget’s original demonstrations, further progress has necessitated the standardization of these problems with materials, questions, procedures, and scoring so clearly specified that examiners can replicate one another’s results. Such standardization permits the explanation of the general applicability of Piaget’s concepts. Standardized tests have been developed for measuring object permanence, egocentricity, and role-taking skills. The Concept Assessment Kit: Conservation, for example, provides six standard conservation tasks for which comparison data (norms) are available for children in several widely diverse cultures. The relative conceptual attainments of an individual child (or culture) can be measured. It is encouraging that those who attain such basic skills as conservation early have been shown to be advanced in many other educational and cognitive achievements.
Implications for Education
Piaget’s views of cognitive development have broad implications for educational institutions charged with fostering such development. The child is viewed as an active seeker of knowledge. This pursuit is advanced by the child’s experimental engagement with problems that are slightly more complex than those problems successfully worked through in the past. The teacher is a facilitator of the opportunities for such cognitive growth, not a lecturer or a drillmaster. The teacher provides physical materials that can be experimentally manipulated. Such materials can be simple: Blocks, stones, bottle caps, and plastic containers all can be classified, immersed in water, thrown into fire, dropped, thrown, or balanced. Facilitating peer relationships and cooperation in playing games are also helpful in encouraging social role-taking and moral development.
Since each student pursues knowledge at his or her own pace and in his or her own idiom, great freedom and variety may be permitted in an essentially open classroom. The teacher may nudge the student toward cognitive advancement by presenting a problem slightly more complex than that already comprehended by the student. A student who understands conservation of number may be ready for problems involving the conservation of length, for example. Yet the teacher does not reinforce correct answers or criticize incorrect ones. Sequencing is crucial. The presentation of knowledge or skill before the child is ready can result in superficial, uncomprehended verbalisms (phrases or sentences that have little or no meaning). Piaget does not totally reject the necessity of the inculcation of social and cultural niceties (social-arbitrary knowledge), the focus of traditional education. He would maintain, however, that an experimentally based understanding of physical and social relationships is crucial for a creative, thoughtful society.