The Development of Knowledge Piagets Theory
349 Infancy and Childhood: Cognitive Development FIGURE 9 .2 Reﬂexes in the Newborn When a ﬁnger is pressed into a newborn’s palm, the grasping reflex causes the infant to hold on tightly enough to suspend its entire weight. And when a newborn is held upright over a ﬂat surface, the stepping reflex leads to walking movements. Voluntary control permits the development of motor skills, allowing the infant to roll over, sit up, crawl, stand, and walk. Until a few years ago, most developmental psychologists accepted Gesell’s view that, except under extreme environmental conditions, these motor abilities occur spontaneously as the central nervous system and muscles mature. Research demonstrates, however, that maturation does not tell the whole story, even in normal environments (Thelen, 1995). Consider the fact that many babies today aren’t learning to crawl on time—or at all. Why? One reason has to do with the “Back to Sleep” campaign begun a decade ago in an effort to prevent sudden infant death syndrome (see the chapter on consciousness). This public health campaign urges parents to put babies to sleep on their backs rather than face down. The campaign has been successful, but researchers have discovered that many babies who were never placed on their tummies went directly from sitting to toddling, skipping the crawling stage but reaching all other motor milestones on schedule (Kolata & Markel, 2001). Observation of infants who do learn to crawl has shown that it does not happen suddenly. It takes the development of enough muscle strength to support the abdomen—and some active experimentation—to get the job done. Six infants in one study tried various crawling techniques—moving backward, moving one limb at a time, using the arms only, and so on (Freedland & Bertenthal, 1994). After a week or two of trial and error, all six infants arrived at the same method: moving the right arm and left leg together, then the left arm and right leg. This pattern turned out to be the most efﬁcient way of getting around quickly without tipping over. Such observations suggest that as maturation increases infants’ strength, they try out various motor patterns and select the ones that work best (Nelson, 1999). In other words, motor development results from a combination of maturation and experience. It is not the result of an entirely automatic sequence that is genetically etched in the brain. Yet again, we see that nature and nurture inﬂuence each other. The brain controls developing behavior, but its own development is affected by experience, including efforts at building motor skills. Infancy and Childhood: Cognitive Development 䉴 How do babies think? In less than ten years, a tiny infant becomes a person who can read a book, write a poem, and argue logically for access to the family’s new computer. What leads to the dramatic shifts in thinking, knowing, and remembering that occur between early infancy and later childhood? Researchers studying cognitive development try to answer this question. The Development of Knowledge: Piaget’s Theory Foremost among these researchers was Jean Piaget, who dedicated his life to a search for the origins of intelligence and the factors that lead to changes in knowledge over the life span. Piaget was the ﬁrst to chart the journey from the simple reﬂexes of the newborn to the complex understandings of the adolescent. Although his theory turned out to be incomplete, and in some respects incorrect, his ideas about cognitive development are still guiding research (Fischer & Hencke, 1996). Intensive observations of infants (including his own) and extensive interviews with children led Piaget to propose that cognitive development proceeds in a series of distinct stages, or periods. He believed that all children’s thinking goes through the same stages, in the same order, without skipping. (Table 9.1 outlines these stages.) According to Piaget, the thinking of infants is different from the thinking of children, which in turn is different from that of adolescents. He said that children are not just miniature 350 TA B L E Chapter 9 9.1 Piaget’s Periods of Cognitive Development According to Piaget, a predictable set of features characterizes each period of children’s cognitive development. The ages associated with the stages are approximate; Piaget realized that some children move through the stages slightly faster or slower than others. Period Activities and Achievements Sensorimotor Infants discover aspects of the world through their sensory impressions, motor activities, and coordination of the two. They learn to differentiate themselves from the external world. They learn that objects exist even when they are not visible and that they are independent of the infants’ own actions. Infants gain some appreciation of cause and effect. Birth–2 years Preoperational 2–4 years 4–7 years Concrete operational 7–11 years Formal operational Over 11 years schemas Mental representations of what we know and expect about the world. assimilation The process of taking in new information about objects by using existing schemas on objects that ﬁt those schemas. accommodation The process of modifying schemas as an infant tries out familiar schemas on objects that do not ﬁt them. sensorimotor period According to Piaget, the ﬁrst stage of cognitive development, when the infant’s mental activity is conﬁned to sensory perception and motor skills. object permanence The knowledge that an object exists even when it is not in view. Human Development Children cannot yet manipulate and transform information in logical ways, but they now can think in images and symbols. They become able to represent something with something else, acquire language, and play games of pretend. Intelligence at this stage is said to be intuitive, because children cannot make general, logical statements. Children can understand logical principles that apply to concrete external objects. They can appreciate that certain properties of an object remain the same, despite changes in appearance, and they can sort objects into categories. They can appreciate the perspective of another viewer. They can think about two concepts, such as longer and wider, at the same time. Only adolescents and adults can think logically about abstractions, can speculate, and can consider what might or what ought to be. They can work in probabilities and possibilities. They can imagine other worlds, especially ideal ones. They can reason about purely verbal or logical statements. They can relate any element or statement to any other, manipulate variables in a scientiﬁc experiment, and deal with proportions and analogies. They can reﬂect on their own activity of thinking. adults and that they are not dumber than adults; they just think in completely different ways at different stages of development. In other words, entering each stage involves a qualitative change from whatever preceded it, much as a caterpillar is transformed into a butterﬂy. To explain how infants and children move to ever higher stages of understanding and knowledge, Piaget introduced the concept of schemas as the basic units of knowledge, the building blocks of intellectual development. As noted in other chapters, schemas are the mental images or generalizations that form as people experience the world. Schemas, in other words, organize past experiences and provide a framework for understanding future experiences. At ﬁrst, infants form simple schemas. For example, a sucking schema combines their experiences of sucking into images of what objects can be sucked on (bottles, ﬁngers, paciﬁers) and what kinds of sucking can be done (soft and slow, speedy and vigorous). Later, children form more complex schemas, such as a schema for tying a knot or making a bed. Still later, adolescents form schemas about what it is to be in love. Two related processes guide this development: assimilation and accommodation. In assimilation, infants and children take in information about new objects by trying out Building Blocks of Development Infancy and Childhood: Cognitive Development 351 existing schemas and ﬁnding schemas that the new objects will ﬁt. They assimilate the new objects into their existing schemas. So when an infant is given a squeaker toy, he will suck on it, thus assimilating it into the sucking schema he has developed with his bottle and paciﬁer. In the same way, a toddler who sees a butterﬂy for the ﬁrst time may assimilate it into her “birdie” schema, because, like a bird, it’s colorful and it ﬂies. Now suppose an older toddler encounters a large dog. How she assimilates this new experience depends on her existing schema of dogs. If she has had positive experiences with the family dog, she will have a positive schema, and, expecting the dog to behave like her pet, she will greet it happily. In other words, past experiences affect what and how children think about new ones. Sometimes, like Cinderella’s stepsisters squeezing their oversized feet into the glass slipper, people distort information about a new object to make it ﬁt an existing schema. When squeezing won’t work, though, people are forced to change, or accommodate, their schemas to the new objects. In accommodation, the person tries out familiar schemas on a new object, ﬁnds that the schemas cannot be made to ﬁt the object, and changes the schemas so that they will ﬁt (see Figure 9.3). So when the infant discovers that the squeaker toy is more fun when it makes a noise, he accommodates his sucking schema and starts munching on the squeaker instead. When the toddler realizes that butterﬂies are not birds because they don’t have beaks and feathers, she accommodates her “birdie” schema to include two kinds of “ﬂying animals”—birds and butterﬂies. And if the child with the positive “doggie” schema meets a snarling stray, she discovers that her original schema does not extend to all dogs and reﬁnes it to distinguish between friendly dogs and aggressive ones. Sensorimotor Development Piaget (1952) called the first stage of cognitive development the sensorimotor period, a time when mental activity is conﬁned to FIGURE 9.3 Accommodation Because the bars of the playpen are in the way, this child discovers that her schema for grasping and pulling objects toward her will not work. So she adjusts, or accommodates, her schema to achieve her goal. schemas about sensory functions, such as seeing and hearing, and to schemas about motor skills, such as grasping and sucking. Piaget believed that during the sensorimotor stage, infants can form schemas only of objects and actions that are present— things they can see, hear, or touch. They cannot think about absent objects, he said, because they cannot act on them. For infants, then, thinking is doing. They do not lie in the crib thinking about their mother or their teddy bear, because they are not yet able to form schemas that are mental representations of objects and actions that are not present. The sensorimotor period ends when infants do become able to form such mental representations. At that point, they can think about objects or actions when the objects are not visible or the actions are not occurring. This milestone, according to Piaget, frees the child from the here-and-now of the sensory environment. It allows for the development of thought. One sign of this milestone is the child’s ability to ﬁnd a hidden object. This behavior reﬂects the infant’s knowledge that an object exists even if it cannot be seen, touched, or sucked. Piaget called this knowledge object permanence. Piaget believed that before infants acquire knowledge of object permanence, they do not search for objects that are placed out of sight. For infants, out of sight is literally out of mind. He said that evidence of object permanence begins to appear when infants are four to eight months old. At this age, for the ﬁrst time, they can recognize a familiar object even if part of it is hidden: They know it’s their bottle even if they can see only the nipple peeking out from under the blanket. Infants now have some primitive mental representations of objects. If an object is completely hidden, however, they will not search for it. Several months later, infants will search brieﬂy for a hidden object, but their search is random and ineffective. Not until they are about eighteen to twenty-four months old, said Piaget, do infants appear able to picture and follow events in their minds. They look for the object in places other than where they saw it last, sometimes in entirely new places. According to Piaget, their concept of object permanence is now fully developed. They have a mental representation of the object that is completely separate from their immediate perception of it.