CHAPTER 5 BRIEF CHAPTER SUMMARY According to Piaget, by acting on the environment, children move through four stages of cognitive development in which psychological structures, or schemes, achieve a better fit with external reality. In the sensorimotor stage, these spans the first two years of life, infants make strides in intentional behavior and understanding of object permanence. By the end of the second year, they become capable of mental representation, as seen in their sudden solutions to problems, mastery of object permanence, deferred imitation, and make-believe play. Displaced reference—the realization that words can be used to cue mental images of things not physically present—emerges around the first birthday and greatly expands toddlers’ capacity to learn about the world through communicating with others. Follow-up research on Piaget’s sensorimotor stage yields broad agreement that many cognitive changes of infancy are gradual and continuous and that various aspects of infant cognition change unevenly. However, many studies suggest that infants display a wide array of understandings earlier than Piaget believed. Secondary circular reactions, understanding of object properties, first signs of object permanence, deferred imitation, problem solving by analogy, and displaced reference of words emerge earlier than Piaget expected. Whereas Piaget thought that young babies constructed all mental representations out of sensorimotor activity, the core knowledge perspective maintains that babies are born with a set of innate knowledge systems, or core domains of thought. These permit a ready grasp of new, related information and therefore support early, rapid development. Information-processing theorists want to determine exactly what individuals of different ages do when faced with a task or problem. They assume that we use mental strategies to operate on information as it flows through three parts of the mental system: the sensory register, the short-term memory store, and the long-term memory store. The central executive, the conscious, reflective part of our mental system, ensures that we think purposefully, to attain our goals. Research indicates that several aspects of the cognitive system improve during childhood and adolescence: (1) the basic capacity of its memory stores, especially working memory; (2) the speed with which information is worked on; and (3) the functioning of the central executive, which directs the flow of information and engages in more sophisticated activities that enable complex, flexible thinking. Gains in executive function—including controlling attention, suppressing impulses, coordinating information in working memory, and flexibly directing and monitoring thought and behavior—are under way in the first two years. By the second half of the first year, infants are capable of recognition as well as recall, and both recognition and recall improve teadily with age. During toddlerhood, categorization gradually ...