Self-Reported Personality Pathology Has Complex Structure and Imposing Simple Structure Degrades Test Information.

Although simple structure is often used as a theoretical guideline for rotation of exploratory factor structures, its empirical foundation is sometimes not investigated. We examined the degree of simple structure in 2 self-report inventories advocated for the description of personality pathology. The multivariate complexity of the inventories was compared against simulated factorial solutions with increasing degrees of simple structure. Results revealed a high degree of complexity in both inventories, regardless of whether focusing on a few broad or many narrow factors and whether items or scales were analyzed. It is concluded that Thurstone's (1934) simple structure criteria are rarely fulfilled in multivariate personality pathology solutions, and, therefore, that alternate rotations represent equally justifiable ways to operationalize the space. Furthermore, using iterative test development to impose simple structure where none originally existed increased standard errors around the factor scores in the interstitial areas between imposed simple structure dimensions. In both simulated and real data, multidimensional item response theory test information functions based on complex solutions demonstrated that test information was uniformly distributed across the space. In contrast, in simple structure solutions, information was weak in areas of the space where nonconforming items had been removed. Implications are discussed.