Using Taxometric Analysis to Distinguish a Small Latent Taxon from a Latent Dimension with Positively Skewed Indicators: The Case of Involuntary Defeat Syndrome

John Ruscio, Elizabethtown College
Ayelet Meron Ruscio, Pennsylvania State University
Terence M. Keane, VA Medical Center


Joining the debate on the structure of depression, S. R. H. Beach and N. Amir (2003) analyzed college students' responses to 6 Beck Depression Inventory (BDI) items with predominantly somatic content and concluded that they identified a small latent taxon corresponding to involuntary defeat syndrome. An exact replication of these analyses yielded virtually identical taxometric results, but parallel analyses of simulated taxonic and dimensional comparison data matching the intercorrelations and skewed distributions of the BDI items showed the results to be more consistent with dimensional than with taxonic latent structure. Analyses in a clinical sample with nonskewed indicators further supported a dimensional interpretation. The authors discuss methodological strategies for conducting and interpreting taxometric analyses under the adverse conditions commonly encountered in psychopathology research, including skewed indicators and small putative taxa.