Environmental influences on development are equally as complex as hereditary factors. The family has an especially powerful impact, operating as a complex and dynamic social system in which members exert direct, indirect, and third-party effects on one another. Socioeconomic status influences child-rearing practices, and poverty and homelessness undermine effective family functioning and children's well-being. The quality of community life, from neighborhoods and schools to small towns and cities, also affects children's development. Cultural values, laws, and government programs shape experiences in all of these contexts.

Child development specialists view the relationship between genetic and environmental factors in different ways. Some believe that it is useful and possible to answer the question of "how much" each contributes to behavior. Others think that heredity and environment cannot be divided into separate influences. They want to discover "how" these two major determinants of development work together in a complex, dynamic interplay.