Beyond the Circumplex model: I. A moratorium on curvilinearity.

The developmental history of Olson's Circumplex Model of Marital and Family Systems, and companion measure, the Family Adaptability and Cohesion Evaluation Scales (FACES), are reviewed with respect to structure, definition, and theory. Cohesion and adaptability are analyzed as multivariate constructs consisting of linear variables that interact in a confounding, systemic fashion. The theory of curvilinearity--the idea that the model's two key dimensions of cohesion and adaptability form a curvilinear rather than linear relationship with effective family functioning--is rejected.