An early and influential analysis from Harris and colleagues indicated that a discrete category, or taxon, may underlie PCL-R psychopathy, allowing it to be measured and analyzed. However, this was only found for the behavioral Factor 2 items they identified, child problem behaviors; adult criminal behavior did not support the existence of a taxon.[14] Marcus, John, and Edens more recently performed a series of statistical analyses on PPI scores and concluded that psychopathy may best be conceptualized as having a "dimensional latent structure" like depression.[15]