The importance of shared environmental influences in explaining the overlap between mother's parenting and sibling...

This article addresses concerns raised by M. C. Neale (1999) in his commentary on the D. A. Bussell et al. (1999) Nonshared Environment in Adolescent Development (NEAD) study. These concerns fall into two categories: (a) model assumptions and sample design and (b) testing of alternative models. The validity of the assumptions of quantitative genetic models is a concern for all researchers in this area. Discussion of those assumptions in this reply is brief and focuses on those most relevant to the NEAD sample. The two alternative models proposed by Neale were designed to provide alternatives to the large shared environmental effect found in the original report of Bussell et al. Because these alternative models did not provide a better fit, the appropriateness of Bussell et al.'s basic model and the importance of shared environmental influences for explaining the association among family subsystems are supported.