<P> Promoting child development through parental training, among other factors, promotes excellent rates of child development . Parents play a large role in a child's life, socialization, and development . Having multiple parents can add stability to the child's life and therefore encourage healthy development . Another influential factor in a child's development is the quality of their care . Child care programs present a critical opportunity for the promotion of child development . </P> <P> The optimal development of children is considered vital to society and so it is important to understand the social, cognitive, emotional, and educational development of children . Increased research and interest in this field has resulted in new theories and strategies, with specific regard to practice that promotes development within the school system . There are also some theories that seek to describe a sequence of states that compose child development . </P> <P> Also called "development in context" or "human ecology" theory, ecological systems theory, originally formulated by Urie Bronfenbrenner specifies four types of nested environmental systems, with bi-directional influences within and between the systems . The four systems are microsystem, mesosystem, exosystem, and macrosystem . Each system contains roles, norms and rules that can powerfully shape development . Since its publication in 1979, Bronfenbrenner's major statement of this theory, The Ecology of Human Development has had widespread influence on the way psychologists and others approach the study of human beings and their environments . As a result of this influential conceptualization of development, these environments--from the family to economic and political structures--have come to be viewed as part of the life course from childhood through adulthood . </P> <P> Jean Piaget was a Swiss scholar who began his studies in intellectual development in the 1920s . Piaget's first interests were those that dealt with the ways in which animals adapt to their environments and his first scientific article about this subject was published when he was 10 years old . This eventually led him to pursue a Ph. D. in Zoology, which then led him to his second interest in epistemology . Epistemology branches off from philosophy and deals with the origin of knowledge . Piaget believed the origin of knowledge came from Psychology, so he traveled to Paris and began working on the first "standardized intelligence test" at Alfred Binet laboratories; this influenced his career greatly . As he carried out this intelligence testing he began developing a profound interest in the way children's intellectualism works . As a result, he developed his own laboratory and spent years recording children's intellectual growth and attempted to find out how children develop through various stages of thinking . This led to Piaget develop four important stages of cognitive development: sensorimotor stage (birth to age 2), preoperational stage (age 2 to 7), concrete - operational stage (ages 7 to 12), and formal - operational stage (ages 11 to 12, and thereafter). Piaget concluded that adaption to an environment (behaviour) is mananged through schemes and adaption occurs through assimilation and accommodation. (1) </P>

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