The study of cognition, which includes thinking and other mental activities such as attention, memory, and problem solving, is a very large area of research in developmental psychology.

1. Piaget's theory of cognitive development
   Piaget's theory was introduced in Chapter 1. We saw that he described the child as actively constructing and building knowledge (schemes) through the processes of assimilation and accommodation to achieve equilibrium in understanding. Piaget was a stage theorist, maintaining that cognition becomes qualitatively reorganized as the child progresses through four stages of cognitive development.
   1. Stages of development
      Piaget believed that cognitive development results from maturational factors and environmental experiences. He specified four stages through which all children progress in an invariable order. The first stage, the sensorimotor stage (birth to two years), is characterized by the child's actions on the environment. The child undergoes three major achievements during this initial stage (which contains six substages). The first accomplishment involves a progression from actions that are reflexive to more goal-directed actions called means-end behavior. The child often displays circular reactions, repetitions of motor acts that produce pleasurable events. A second accomplishment involves the child's gradual changing focus from the self to a greater orientation to the external world. Another accomplishment in this initial stage is the attainment of the object concept, or object permanence. Children who reach this stage understand that objects continue to exist even though they are not in immediate sight or within reach to be acted upon.
      Possession of the object concept is necessary for the development of deferred imitation, the ability to imitate a model who is no longer present, and marks the end of the sensorimotor stage and the beginning of the preoperational stage. During this second stage (about two to seven years), the child develops the semiotic function, the ability to use a symbol; this function is an important prerequisite for language, imagery, fantasy play, and drawing. Preoperational thought, however, has several distinct limitations. Children in this stage are described as egocentric, because they are unable to separate their own perspective from that of others. Another limitation of the preoperational child is revealed through a series of assessment tasks, called conservation tasks, that require the child to make a judgment about the equivalence of two displays following the observation of a transformation of one of the displays (e.g., the conservation of liquid task). According to Piaget, conservation errors result from centration (focusing on only one aspect of the problem), lack of reversibility, and the tendency of the child to focus on states rather than on the events that occur between two related states.
      The child's ability to solve conservation tasks signals the beginning of the third stage, the concrete operational stage (about seven to eleven years). The ability to solve conservation tasks results from the child's ability to perform mental activities, or operations, such as reversibility.
      By the fourth stage, the formal operational stage (about eleven years and beyond), the child thinks logically and abstractly and demonstrates hypothetical reasoning. According to Piaget, no further qualitative changes in cognitive growth occur once the child achieves the formal operational stage, although adult thinking may continue to grow. Other characteristics of adolescent thought, proposed by David Elkind, include the imaginary audience, the sense that others are continuously examining and evaluating the adolescent, and the personal fable, the sense that one is unique and invulnerable.
   2. Implications for education
      Piaget's theory of cognitive development has several implications for education. First, it suggests that the educator consider the child's current stage of development and design individual plans of instruction that match the child's abilities. Second, it encourages the active engagement of the child with tasks that are one step beyond his or her current state of knowledge. Several educational programs based on Piagetian models have emerged, each emphasizing different aspects of Piaget's theory.
   3. Evaluating Piaget's theory
      Piaget's theory has generated an enormous volume of empirical research in developmental psychology. The results of many of these experiments, however, have raised questions about several aspects of Piaget's theory. Several lines of research suggest that Piaget may have underestimated the ages at which children attain cognitive skills.
      
      

      Examining Research Methods: Ensuring Experimental Control in Studying the Object Concept A major topic of research concerning age of acquisition of a cognitive skill bears on the infant's knowledge of object permanence. Work by Baillargeon has suggested that infants as young as three months of age may know that an object continues to exist when out of sight. Various control procedures have been initiated to eliminate potential alternative reasons why three-month-olds are surprised when a screen appears to rotate "through" a hidden object. However, some researchers believe that other explanations can account for why the looking behavior of infants this young appears to suggest that they are capable of object permanence.

      
      Piaget saw development as stagelike. This notion posits great consistency in children's performance within a stage of development and predicts a high correlation among various abilities within a stage. Modern research, however, has found greater inconsistencies within a stage than would be expected and has failed to find high correlations among the various abilities within a stage. These results have led many contemporary psychologists to view development more as a continuous process and less as the stagelike process that Piaget envisioned.
      Others propose that cognitive development is more domain-specific, that is, takes place on specific topics, than domain-general, that is, applies to all aspects of knowledge as Piaget had proposed.
      Some modern researchers also challenge Piaget's suggestion that the mechanism of development involves alteration of cognitive structures such as symbolic, logical, and hypothetical thought. Current research suggests that perhaps the mechanism of cognitive development involves changes in how information is gathered, manipulated, and stored.
      The heavy emphasis Piaget placed on maturation has also been criticized. Researchers have pointed out that some individuals never achieve formal operational thinking. Specific cultural experiences have been observed to accelerate the development of formal operational thought. These observations suggest that the child's sociocultural experiences may shape cognitive development to a greater degree than Piaget acknowledged.
      Despite the modern criticisms of Piaget's theory, several of his ideas are well accepted today, such as his view of the child's active role in development and his assumption that the child's knowledge at any given time determines what further knowledge the child can acquire.
      
      
2. Concept development
   The child's use of concepts, or the way in which the child organizes information on the basis of some general or abstract principle, increases the efficiency of cognitive processing. For example, concepts make possible the classification of pieces of information on the basis of common properties or themes.
   1. Properties of objects
      The first concepts are those related to the properties of objects. Debate exists about whether object concepts are understood before six months of age. Some researchers claim that three- and four-month-old infants understand object permanence as well as several other properties of objects such as size constancy, height, and rigidity. Infants under seven months of age may have a limited ability to inhibit reaching for an object that had been hidden in a given location even though they may understand that the object is no longer hiding there (the "A, not B" error). Infants seem to understand the concept of solidity, the fact that one object can not pass through the space occupied by another object. Disagreement concerning the interpretation of these facts remains. Some researchers believe that young infants possess innate knowledge concerning important fundamental properties of objects (the core knowledge hypothesis). However, others believe that perceptual differences in the experimental situations can explain the research findings. Six-month-old infants also have some understanding of physical causality. However, from infancy to seven or eight years of age, the child displays increasingly sophisticated awareness of physical causality. For example, young children may exhibit animism, attributing lifelike qualities to inanimate objects, and artificialism, the belief that naturally occurring events are caused by people--although the way in which young children are questioned appears to influence the likelihood of such responses.
   2. Classification
      Classes can be based on perceptual groupings (objects that look alike), thematic relations (objects that function together or complement one another), or taxonomic groupings (based on some abstract principle). Children's earliest classifications (before about nine to twelve months) appear to be largely perceptually based. This reliance on shared perceptual features decreases with age, particularly as children begin to understand hierarchical relations among objects that are perceptually dissimilar. Initial groupings of objects tend to occur at a basic level: objects go together when they look alike or are used in similar ways. However, some researchers argue that categories are formed on the basis of meaning even before one year of age. Some concepts or categories are easier to grasp than others because they are in natural domains; that is, they are biological entities that exist in the world. Cross-cultural studies suggest that the development of taxonomic classifications may require direct instruction through formal schooling, either by providing instruction on taxonomic classification or by fostering abstract thought.
   3. Numerical concepts
      Piaget argued that preoperational children do not possess numerical concepts; that is, they lack a full grasp of the meaning of number. According to Piaget, the preoperational child's failure to conserve number results from the failure to understand the one-to-one correspondence that exists between the items of each row in the conservation task and from the failure to attain an understanding of cardinality and ordinality. Current research, however, suggests that Piaget underestimated the preoperational child's understanding of number concepts. Children as young as three and four years understand that number terms include quantitative relations (e.g., "smaller" and "larger"), and preoperational children understand the additive properties of numbers. Even newborns and very young infants may be able to detect differences between small numbers of objects, although whether this ability is on the basis of number or other criteria such as amount of contour is more difficult to determine. Once children enter school, they engage in more formal learning of mathematics. However, preschoolers have some understanding of complex numerical concepts including fractions. Students from Asian countries score consistently higher on tests of mathematics than students from the United States. Factors that may contribute to this difference include the learning of more effective strategies for solving mathematics problems.
   4. Spatial relationships
      Children also organize information in terms of their location in physical space. Children initially locate objects by relying on the positions of their own bodies, particularly if no external environmental cues are available. When landmarks, or distinct cues, are available, preschool-age children make sufficient use of them to locate objects in large spatial environments. Children's abilities to use maps improves when experimenters highlight the connection between objects on the map and objects in physical space.
      
      
3. Understanding psychological states
   
   1. Perspective taking: taking the views of others
      An important ability necessary for understanding and interacting with others is perspective taking, the ability to put oneself in another person's place. Piaget and Inhelder described four-to-six-year-olds as displaying considerable egocentrism when evaluating the visual perspectives of others. More recent research suggests that children as young as three to four years can identify the perspectives of others reasonably well.
      John Flavell distinguishes between two levels of visual perspective-taking skill. At the first level (late infancy to about three years), children realize that their views do not always match others' views. At the second level (age three years and onward), children become increasingly proficient at determining the specific limitations of others' views.
   2. The child's theory of mind
      As children develop cognitively, they gain an increasingly coherent appreciation of the mental states of themselves and others. Piaget was clear in his view that preoperational children have no knowledge about the nature of thought. Instead they display realism, in that they cannot distinguish between mental and physical entities until the school years. Recent research suggests, however, that by the time they enter school, children have a well-developed "theory of mind." Using a "false belief" task, researchers have shown that four-year-olds are aware of the content of another person's beliefs. Research with children from several cultures has shown similar developmental changes in their understanding of "beliefs," suggesting that a theory of mind may have a biological basis. On the other hand, the influence of socialization experiences is suggested by findings that family size, conversational experiences, and language capabilities are among a number of factors related to success on false-belief tasks.
      
      

      Atypical Development: Childhood Autism Numerous theories have been advanced to explain the causes of autism, a severe psychological disorder that affects about one or two out of every thousand children born. A recent suggestion is that autistic children fail to develop a "theory of mind." As a result of this possible lack of knowledge of the mental states of others, autistic children may suffer from severe deficits in communication and social interaction.

      
      
4. Neo-Piagetian approaches
   One criticism of Piaget's theory concerns how broad and general the features of a child's thinking are within a given stage of development, referred to as domain-general or domain-specific knowledge. Several theorists have modified and expanded on Piaget's theory to deal with this criticism.
   1. Fischer's skill theory
      Kurt Fischer suggests that transitions in thinking in cognitive development occur at different rates in specific domains or skills rather than simultaneously in all domains.
   2. Case's theory
      Robbie Case's theory, like Piaget's and Fischer's, proposes four stages of cognitive development, but it differs in the explanation of transitions from one stage to the next. According to Case, developmental change occurs through an emphasis on experience and maturation and efficiency in the organization and speed of cognitive processing.
      
      
5. Vygotsky's sociocultural theory of cognitive development
   Vygotsky, in contrast to Piaget, emphasized that development must be understood within the context of the culture in which a child is reared. The social activity surrounding formal and informal exchanges with others plays a significant role in development.
   1. Scaffolding
      Others provide a scaffolding for cognitive development, that is, temporary support by demonstrating cognitive skills and techniques in which the child is deficient and that the child eventually incorporates as part of her or his own thinking. The zone of proximal development stresses that the most effective help the child can receive from an expert is assistance just slightly beyond his or her capacities, thereby building on the child's current level of competence.
   2. The role of skilled collaborators
      Research indicates that in general, when children work with a skilled collaborator (whether an adult or a peer), performance on cognitive tasks improves. Cross-cultural research reveals that cultures differ in how parents guide the child in becoming a responsible participant in society. In some cultures, children acquire skills primarily through caregiver support and assistance; in other cultures, a focus on play and conversation between child and caregiver is supplemented with more formal lessons and educational opportunities. An important component in effective collaboration is shared attention and communication, known as intersubjectivity.
      
      

      Research Applied to Education: Reciprocal Teaching Educational programs concerned with reciprocal teaching build on Vygotsky's theory of development by providing strategies and a scaffold for learning academic skills, encouraging instruction within the child's zone of proximal development, inviting students to more actively take charge of their own learning, and allowing students to take over the teaching process itself. When interactions between teachers and students are conducted in accordance with Vygotsky's ideas, cognitive skills can be enhanced substantially.