SUMMARY
This review focuses on conceptualizations of nonshared environment and on four areas of research that should be targeted for future growth. It is argued that there are at least two different approaches to the study of nonshared environment. “Experience-oriented” researchers center on sibling differential experiences in the family and their role in children's development. “Outcome-oriented” investigators focus on the search for environmental origins of individual differences in outcomes. Turkheimer and Waldron's (2000) concept of objective versus effective nonshared environment and Reiss and colleagues' (2000) notion of single-system versus multi-system nonshared environment processes are also discussed. Four topics for future research are outlined: (1) age-related changes and development; (2) the role of the self; (3) the role of context; and (4) the importance of extrafamilial experiences. More work in these areas will lead to useful theories of how nonshared environment processes are linked to sibling and individual differences in behavioral development and adjustment.