Piaget’s theory of cognitive development is a stage theory, a type of theory suggesting that all human beings move through an orderly and predictable series of changes. We’ll have reason to examine other stage theories in our discussions of adult development and personality.
Currently, however, many psychologists question the ideas, basic to such theories, that (1) all human beings move through a set series of stages; (2) they move from one stage to another at specific ages; and (3) the order of such progress is unchanging. There simply seems to be too much variability among individuals to enable us to assume such a high degree of orderliness in human development.
Having clarified this point, let’s return to Piaget’s theory, and begin by noting that central to it is the assumption—often known as constructivism—that children are active thinkers who are constantly trying to construct more accurate or advanced understanding of the world around them. In other words, from this perspective, children construct their knowledge of the world by interacting with it.
How do children build such knowledge? According to Piaget, through two basic processes. The first of these is assimilation, which involves the incorporation of new information or knowledge into existing knowledge structures known as schemas.
A schema is a kind of “cognitive scaffold”—a framework for holding knowledge and organizing it. The second process is accommodation; it involves modifications in existing knowledge structures (schemas) as a result of exposure to new information or experiences. Here’s a concrete example of how, in Piaget’s theory, these processes operate.
A two-year-old child has seen many different kinds of cats and, on the basis of such experience, has built up a schema for cats relatively small four-legged animals. Now she sees a squirrel for the first time and through assimilation includes it in this schema. As she encounters more and more squirrels, however, she begins to notice that they differ from cats in several respects: They move differently, climb trees, and have much bushier tails, and so on. On the basis of this new experience, she gradually develops another schema for squirrels.
This illustrates accommodation changes in our existing knowledge structures resulting from exposure to new information. Piaget believed that it is the tension between these two processes that encourages cognitive development. But don’t lose sight of the key fact. According to Piaget, as these changes occur, children are constantly trying to make better and more accurate sense out of the complex world around them. Let’s now take a closer look at the discrete stages of cognitive development Piaget described.
Piaget suggested that the first stage of cognitive development lasts from birth until somewhere between eighteen and twenty-four months. During this period, termed the sensorimotor stage, infants gradually learn that there is a relationship between their actions and the external world. They discover that they can manipulate objects and produce effects.
In short, they acquire a basic grasp of the concept of cause and effect. For example, they learn that if they make certain movements—for instance, shaking their leg—specific effects follow (for instance, toys suspended over their crib also move), and they begin to experiment with various actions to see what effects they will produce.
Throughout the sensorimotor period, Piaget contended, infants seem to know the world only through motor activities and sensory impressions. They have not yet learned to use mental symbols or images to represent objects or events. This results in some interesting effects. For example, if an object is hidden from view, four-month-olds will not attempt to search for it. For such infants, “out of sight” is truly “out of mind.”
By eight or nine months of age, however, they will search for the hidden objects. They have acquired a basic idea of object permanence—the idea that objects continues to exist even when they are hidden from view.
Sometime between the ages of eighteen and twenty-four months, Piaget suggested, toddlers acquire the ability to form mental images of objects and events. At the same time, language develops to the point at which they begin to think in terms of verbal symbols—words. These developments mark the transition to Piaget’s second stage—the preoperational stage. This term reflects Piaget’s view that at this stage, children don’t yet show much ability to use logic and mental operations.
During the preoperational stage, which lasts until about age seven, children are capable of many actions they could not perform earlier. For instance, they demonstrate symbolic play, in which they pretend that one object is another—that a pencil is a rocket or a wooden block is a frog, for example. Such play is marked by three shifts that afford unique insights into how children’s cognitive abilities change during this period.
One is decentration, in which children gradually begin to make others rather than themselves the recipients of their playful actions—for instance, they begin to feed their dolls or dress them. The second shift is decontextualization: Objects are made to substitute for each other, as when a child pretends that a twig is a spoon.
The third change involves integration combining play actions into increasingly complex sequences. Can you see how children’s abilities to engage in more and more complex forms of play indicate that they are growing cognitively? After all, in order to imagine that one object is another and to conduct long play sessions in which dolls are treated as though they had thoughts and feelings of their own, a child must have a growing ability to think in terms of words.
While the thought processes of preoperational children are more advanced than those in the preceding stage, Piaget emphasized that these children are still immature in several respects. True, they can use mental symbols; but their thinking remains somewhat inflexible, illogical, fragmented, and tied to specific contexts.
One way in which the thinking of preoperational children is immature involves what Piaget termed egocentrism—children’s inability to understand that others may perceive the world differently than they do. For example, if two- year-olds are shown a card with a picture of a dog on one side and a cat on the other, and the card is placed between the child and the researcher, many do not seem to realize that they and the adult see different pictures. (Again, however, Piaget seems to have underestimated the abilities of young children)
Children in the preoperational stage also seem to lack understanding of relational terms such as lighter, larger, softer. Further, they lack serration— the ability to arrange objects in order along some dimension. Finally, and most important, they lack a grasp of what Piaget terms the principle of conservation knowledge that certain physical attributes of an object remain unchanged even though the outward appearance of the object is altered.
For example, imagine that 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.
By the time they are six or seven, most children can solve the simple problems described above. According to Piaget, a child’s mastery of conservation marks the beginning of a third major stage known as the stage of concrete operations.
During this stage, which lasts until about the age of eleven, many important skills emerge? Children gain understanding of relational terms and serration. They come to understand reversibility, the fact that many physical changes can be undone by a reversal of the original action.
Children who have reached the stage of concrete operations also begin to engage in what Piaget described as logical thought. If asked, “Why did you and your mother go to the store?” they reply, “Because my mother needed some milk.” Younger children, in contrast, may reply “Because afterwards, we came home.”
At about the age of twelve, Piaget suggested, most children enter the final stage of cognitive development, the stage of formal operations. During this period, major features of adult thought make their appearance. While children in the earlier stage of concrete operations can think logically, they can do so only about concrete events and objects.
In contrast, those who have reached the stage of formal operations can think abstractly; they can deal not only with the real or concrete but with possibilities events or relationships that do not exist, but can be imagined.
During this final stage, children become capable of what Piaget termed hypothetic deductive reasoning. This involves the ability to generate hypotheses and to think logically about symbols, ideas, and propositions. Children at the stage of formal operations also became capable of engaging in interpropositional thinking, thinking in which they seek to test the validity of several propositions. (Children at the level of concrete operations can sometimes test single propositions.)
While the thinking of older children or adolescents closely approaches that of adults, however, Piaget, believed that still falls short of the adult level. Older children, and especially adolescents, often use their new powers of reasoning to construct sweeping theories about human relationships, ethics, or political systems. The reasoning behind such views may be logical, but the theories are often false, because the young persons who construct them don’t have enough experience or information to do a more sophisticated job.
One final but crucial point- even though people who have reached the stage of formal operations are capable of engaging in advanced forms of thought, there is no guarantee that they will actually do so. Such thinking requires lots of cognitive effort, so it is not surprising that adolescents, and adults too, often slip back into less advanced modes of thought.