Ecological systems theory is a broad term used to capture the theoretical contributions of developmental psychologistUrie Bronfenbrenner.[1] Bronfenbrenner developed the foundations of the theory throughout his career,[2] published a major statement of the theory inAmerican Psychologist,[3] articulated it in a series of propositions and hypotheses in his most cited book,The Ecology of Human Development and further developing it inThe Bioecological Model of Human Development and later writings.[4][5][6] A primary contribution of ecological systems theory was to systemically examine contextual variability in development processes. As the theory evolved, it placed increasing emphasis on the role of the developing person as an active agent in development and on understanding developmental process rather than "social addresses" (e.g., gender, ethnicity) as explanatory mechanisms.[6]
Ecological systems theory describes a scientific approach to studying lifespan development that emphasizes the interrelationship of different developmental processes (e.g., cognitive, social, biological). It is characterized by its emphasis on naturalistic and quasi-experimental studies,[6] although several important studies using this framework use experimental methodology.[2] Although developmental processes are thought to be universal, they are thought to (a) show contextual variability in their likelihood of occurring, (b) occur in different constellations in different settings and (c) affect different people differently. Because of this variability, scientists working within this framework use individual and contextual variability to provide insight into these universal processes.[6]
The foundations of ecological systems theory can be seen throughout Bronfennbrenner's career.[2] For example, in the 1950s he analyzed historical and social class variations in parenting practices,[7] in the 1960s[8] he wrote an analysis of gender differences focusing on the different cultural meanings of the same parenting practices for boys and girls, and in the 1970s he compared childrearing in the US and USSR,[9] focusing how cultural differences in the concordance of values across social institutions change parent influences.
The formal development of ecological systems theory[6] occurred in three major stages.[6] A major statement of the theory was published inAmerican Psychologist.[3] Bronfenbrenner critiqued then current methods of studying children in laboratories as providing a limited window on development, calling it "the science of the strange behavior of children in strange situations with strange adults for the briefest possible periods of time" (p. 513) and calling for more "ecologically valid" studies of developing individuals in their natural environment. For example, he argued that laboratory studies of children provided insight into their behavior in an unfamiliar ("strange") setting that had limited generalizability to their behavior in more familiar environments, such as home or school.[3]The Ecology of Human Development[4] articulated a series of definitions, propositions and hypotheses that could be used to study human development. This work categorized developmental processes, beginning with genetic and personal characteristics, though proximal influences that the developing person interacted with directly (e.g., social relationships), to influences such as parents' work, government policies or cultural value systems that affected them indirectly.[10] As the theory evolved, it placed increasing emphasis on the role of the developing person as an active agent in development and on understanding developmental process rather than "social addresses" (e.g., gender, ethnicity) as explanatory mechanisms.[6] The final form of the theory, developed in conjunction withStephen Ceci, was called theBioecological Model of Human Development[5][6] and addresses critiques that previous statements of the theory under-emphasized individual difference and efficacy.[6][2] Developmental processes were conceived of as co-occurring in niches that were lawfully defined and reinforcing.[11] Because of this, Bronfenbrenner was a strong proponent of using social policy interventions as both a way of using science to improve child well-being and as an important scientific tool.[3] Early examples of the application of ecological systems theory are evident inHead Start.[12][13]

Later work by Bronfenbrenner considered the role of biology in this model as well; thus the theory has sometimes been called thebioecological model.[16]
Per this theoretical construction, each system contains roles, norms and rules which may shape psychological development. For example, an inner-city family faces many challenges which an affluent family in agated community does not, and vice versa. The inner-city family is more likely to experience environmental hardships, like crime and squalor. On the other hand, the sheltered family is more likely to lack the nurturing support of extended family.[17]
Since its publication in 1979, Bronfenbrenner's major statement of this theory,The Ecology of Human Development[18] has had widespread influence on the way psychologists and others approach the study of human beings and their environments.[19] As a result of his groundbreaking work inhuman ecology, 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.
Bronfenbrenner has identified Sovietdevelopmental psychologistLev Vygotsky and German-born psychologistKurt Lewin as important influences on his theory.
Bronfenbrenner's work provides one of the foundational elements of theecological counseling perspective, as espoused byRobert K. Conyne, Ellen Cook, and theUniversity of Cincinnati Counseling Program.
There are many different theories related to human development. Human ecology theory emphasizes environmental factors as central to development.[15]
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