Cognition is the mental activity and behavior that allows us to understand the world. It includes the functions of learning, perception, memory, and thinking; and it is influenced by biological, environmental, experimental, social, and motivational factors. A variety of theories have been proposed to explain the pattern of cognitive development observed in children. PIAGET'S THEORY OF COGNITIVE DEVELOPMENTThe Evolution of Piaget's ThinkingBeginning in the early 1960s, Piaget's theory began to replace behaviorism in America. Unlike behaviorism, this theory was seen as truly developmental because it allowed for the different capacities of children of different ages. Piaget based his theory on observations of his own and other children as they answered questions during unstructured interviews.The Child as an Active Seeker of KnowledgeAccording to Piaget, children actively seek out information and adapt it to the knowledge and conceptions of the world that they already have. Thus, children construct their understanding of reality from their own experience. Children organize their knowledge into increasingly complex cognitive structures called schemata. Children possess many different schemata, and these change as the children develop. In the newborn, the schemata take the form of innate reflexes and reaction patterns, like sucking. As the child grows and gains experience, the schemata shift from motor activities to mental activities called operations. These operations become increasingly complex with age. Piaget suggested that schemata are modified according to the principles of organization and adaptation, which continue to operate throughout the life span. Organization is the predisposition to combine simple physical or psychological structures into more complex systems. Adaptation involves the two complementary processes of assimilation, or fitting new experiences into current cognitive schemata, and accommodation, or adjusting current schemata to fit the new experiences. Most encounters involve both processes. PIAGET'S STAGES OF COGNITIVE DEVELOPMENT Piaget divided intellectual development into four unique periods that are indicative of the changes in children's cognitive structures. The attainments of earlier stages are essential for those in later periods of development. All children go through the stages in the same order, although not necessarily at the same ages. The Sensorimotor Period (0 to 2 Years). )During the first two years of life, called the sensorimotor period, a child makes the transition from relying on reflexes to using internal representation, which is the cornerstone of symbolic thought. Piaget divided this period into six substages, during which the child physically explores the environment, developing abilities such as symbolic thought and deferred imitation. Throughout these substages, which include reflex activity, primary circular reactions, secondary circular reactions, coordination of secondary schemata, tertiary circular reactions,and inventing new means by mental combination, children gradually come to understand object permanence. Critics of Piaget have suggested that children acquire this concept as well as other knowledge about the properties of objects and such principles of the physical world as causality earlier than Piaget thought.The Preoperational Period (2 to 7 Years)The major development milestone during the preoperational period (2-6/7 years) is the development of the symbolic function, or the ability to use symbols such as words, images, and gestures to represent objects and events. This can be seen in the rapid development of language, in imaginative play, and in an increase in deferred imitation. Piaget divided this stage into the preconceptual stage(2-4 years) and the intuitive stage (4-6/7 years). During the preconceptual period, children's thinking is limited by animistic thinking, the tendency to attribute lifelike characteristics to inanimate objects, and by egocentricity, an inability to see things from another person's perspective. A shift away from egocentrism may be related to the development of role-taking abilities. During the intuitive stage, children are able to use certain mental operations, but they do not seem to be aware of the principles used because they cannot explain them. Limitations in their thinking are still found in problems involving seriation, part-whole relations, and conservation. The most important acquisition of the preoperational period is an elementary understanding of the notion of conservation. Typically, the child learns to conserve number at the end of this period but cannot yet conserve other characteristics such as mass and volume. The concept of horizontal decalage explains this unevenness of children's cognitive achievements. In recent years, however, critics have suggested that children may achieve notions of conservation earlier than Piaget believed. Piaget believed that three characteristics of preoperational thought limit children's thinking. The first is the child's inability to understand reversibility, or the notion that all logical operations are reversible. The second is the tendency to focus on the end states of change rather than on the process of transformation. The third characteristic is centration or focusing on only one dimension of a problem. The Period of Concrete OperationsDuring the concrete operational period (6/7-11 years) children can perform most of the tasks that they were unable to master in the preceding stage, including conservation of various substances and characteristics, classification, and seriation. The Period of Formal OperationsChildren in the formal operations period (11/12 years on) can use flexible and abstract reasoning, test mental hypotheses, and consider multiple possibilities for the solution to a problem. Not all children or adults attain this stage. The use of symbolic skills and higher education are among the factors associated with formal operations.Self and Other: Piagetian Concepts and the Beginning of Social CognitionAlthough Piaget did not emphasize the child's learning to distinguish self from other, his concepts of egocentrism and object permanence have clear implications for this process and the beginnings of social cognition. EVALUATION OF PIAGET'S THEORYStrengths of the TheoryPiaget's theory integrates and illuminates a broad spectrum of diverse issues revolving around children's understanding and use of knowledge, and it has stimulated an enormous amount of research. Among the most significant of Piaget's many heuristic ideas are that children actively construct their knowledge of the world, that the errors they make provide important clues about their thinking, and that cognitive development can be discerned in perceptual-motor behavior as well as in language skills.Did Piaget Judge the Child's Abilities Accurately??Current evidence indicates that infants and children grasp many concepts, such as object permanence, causality, conservation, and the perspectives of another, considerably earlier than Piaget thought.Does Cognitive Development Proceed in Stages??Research also suggests that the sequence of development may not be invariant as Piaget believed, that it may be modified by cultural experiences, and the development may not occur in the distinct and qualitatively different stages Piaget proposed.Overall AssessmentIt is largely thanks to Piaget's work, however, that the field of cognitive development owes its ascendancy. Despite flaws in his theorizing and methods, Piaget asked and proposed answers to important questions in an innovative way, simulating the work of other investigators. VYGOTSKY'S SOCIOCULTURAL THEORYElementary and Higher mental Mental FunctionsVygotsky's theory emphasizes the critical role played by the social world in facilitating the child's development. According to his theory, children generally internalize thought processes that first occur through interaction with others in the social environment. Qualitative transitions between elementary mental functions and higher mental functions occur because of shifts in the use of mediators such as language and other symbols. The acquisition and use of language plays a primary role in children's developing intellectual abilities.The Zone of Proximal DevelopmentVygotsky's interest in the child's potential for intellectual growth led him to develop the concept of the zone of proximal development. In recent years this concept has led to the use of scaffolding, an instructional process in which the teacher adjusts the amount and type of support offered to the child to suit the child's abilities, withdrawing support as the child becomes more skilled.The Role of CultureTwo principles of cultural influence Vygotsky's theory: First, cultures vary widely in the kinds of institutions and settings they offer to facilitate children's development, and second, in assessing children's cognitive development, unless we consider these variations and cultural contexts we may seriously underestimate children's cognitive development. MATHEMATICS AND CULTUREThe Role of LanguageLanguage plays an important role in Vygotskian theory. As children begin to use social speech, egocentric speech,and inner speech, they learn to communicate and to form thoughts and regulate intellectual functions. EVALUATION OF VYGOTSKY'S THEORY Vygotsky drew attention to the importance of the social context in which learning and the evolution of cognitive skills take place and to the influence of peers and adults on the child's development. He pointed out that the particularities of a given culture determine the nature and manner of functioning of the societal institutions that influence how children think and learn. The resulting research interest in the effect of cultural variation on the child's development has created a focus that is especially useful in multiethnic societies like the United States. Vygotsky's theory does not provide the richness that Piaget's approach offers, and he did not provide the kinds of specific tools for research that Piaget's many tests and experiments have given us. Vygotsky's approach offers only a general outline of cognitive development; in its emphasis on the social and cultural aspects of learning and cognition, however, it challenges future researchers to explore the role of context in greater depth.