The notion of “nonshared environment” (NSE) has been a powerful concept in the field of developmental psychology for over three decades. It refers to environmental influences that are specific to one member of a twin or sibling pair, yet not shared by the other. NSE has been associated with a wide range of outcomes, including cognitive, psychological, and social development. The potential for NSE to explain individual differences in development has been explored extensively, and this article will review the research in this area, as well as discuss the implications of NSE for both theoretical and practical purposes.
Recent advances in the understanding of NSE have been driven primarily by studies of twins. By comparing the behavior of identical twins who share the same genetic makeup to fraternal twins who share only half of their genes, researchers can isolate environmental factors as a source of variation in behavior. These studies have found that NSE influences a wide range of outcomes, including academic achievement, psychological adjustment, and even moral reasoning.
Other research suggests that NSE has a significant effect on behavior even when controlling for genetic differences. Studies using genetically informed designs, such as adoption and sibling-comparison designs, have consistently shown that NSE factors such as parenting, socialization, and peer influences can have a major impact on development. For example, findings from a recent study by Paley et al. (2019) suggest that parenting style is a significant predictor of the academic achievement of siblings, even when controlling for genetic factors.
The implications of NSE for both theoretical and practical purposes are far-reaching. On a theoretical level, NSE helps to explain why individuals within the same family can have such different experiences and outcomes, even when raised in a similar environment. On a practical level, understanding NSE gives us insight into how to best support and nurture children, as well as how to help families address issues of inequality and disadvantage.
In conclusion, research on NSE has revealed that environmental influences such as parenting, socialization, and peer influences can have a significant impact on development, even when controlling for genetic factors. Understanding the importance of NSE allows us to better understand individual differences in development, and has implications for both theoretical and practical purposes.
References
Paley, B., Glick, J. E., & Smith, J. R. (2019). Parenting style as a predictor of academic achievement in siblings: A genetically informed study. Developmental Psychology, 55(10), 2146-2158.