Child Development The first two years of life, known as infancy, is universally recognized as an extremely important stage of human development, and is therefore distinguished from the later stages. Infancy witnesses the rapid growth of the child's cognitive, psychosocial, and biosocial development, and the infant's increasing responsiveness to the environment and the people within that environment.

Infants grow at a very rapid rate during the first one and a half years of life, developing not only physically, but also mentally, emotionally, and socially. The infant's brain is immature at birth, and the child's early behavior therefore involves the display of a set of reflexes: some that occur in response to the infant's adjustment to its new environment and stimuli and others that are present because the cerebral cortex is not yet mature enough to control them. Infants appear particularly attentive to visual stimuli, such as movement, contrast, color, and symmetry. During the first year, maturation of the brain occurs at a rapid rate and, when combined with innate perceptual biases and post-natal experiences, the infant develops two important psychological structures: perceptual schemata and conditioned responses. As the brain develops, a child responds more and more to sight and sound, which prepares them for further development.

Cognitive development relates to the reasoning and logic of an infant. Jean Piaget suggested the existence of a mental structure - sensorimotor coordination - that combines a schema with action. According to Piaget, infants acquire knowledge about objects through their actions with them, and that this occurs through a series of stages that make up the sensorimotor period. Early in the first year infants progress from automatic reflex responses to primary circular reactions, in which they repeat actions that initially occurred accidentally. Later they develop secondary circular reactions, in which they repeat actions that create interesting sights and sounds. After about twelve months they form tertiary circular reactions, in which they vary their actions rather than...

In the final stage of the sensorimotor period children invent new schemes by imagining events and outcomes. Piaget also observed the development of the concept of object permanence: the belief that objects continue to exist even when they are out of sight. He believed that this concept develops as a result of the child's prior interactions with the object. The four basic assumptions about the nature of development during the first two years of life are: (a) interaction with the environment is an essential facilitator of development; (b) psychological growth during infancy is continuous; - there is a connection between successive periods of development; and (d) increased intentionality is one of the major competencies to develop in the first two years of life. Other theorists have questioned these assumptions and Piaget's insistence on the necessity of sensorimotor actions for cognitive development.
Infants display many reactions that suggest the development of emotional states. One of the most common of these (exhibited late in the first year of infancy) is stranger anxiety. At around this time, infants also display a fear of temporary separation from their primary caregiver. Most theorists assume that the pattern of social interaction between the infant and the caregiver influences the infant's future psychological growth and development. A major result of the infant-parent interactions is the development, within the infant, of an emotional attachment to the caregiver. All normal infants form attachments, and many theorists propose that a strong or secure attachment provides a basis for healthy emotional and social development during later childhood, and adulthood.

Human development is one of the most popular, and controversial, areas of interest for those who study psychology. Freud and Erikson are two respected theorists with vastly differing ideas concerning human development, although both based their theories on the concept of the individual passing through stages in human development. Freud's ideas on human development…