A circumplex can be viewed in three successively more restrictive and testable ways. First, a circumplex can be viewed as merely a useful pictorial representation of a particular domain. Second, a circumplex can be viewed as implying circular order, such that variables that fall close together are more related than variables that fall further apart on the circle, with opposite variables being negatively related and variables at right angles being unrelated (orthogonal). Third, a circumplex can be viewed as implying exact circumplex structure, such that all variables are equally spaced around the circle (Wiggins & Trobst, 1997). Sophisticated psychometric and geometric tests can be applied to determine whether a circumplex meets the criteria of exact circumplex structure (Acton & Revelle, 1999).