Comparison of the Halstead Category Test and the revised Category Test: comment on Russell and Levy

Russell and Levy recently published an article describing a new shortened version of the Halstead Category Test. They compared their revised Category Test (RCAT) with the Category Test (CAT) and reported it to be highly correlated with and as accurate as the CAT in predicting the presence or absence of brain damage. However, they substantially modified the CAT and claimed the two versions to be comparable without having administered the RCAT to a single person. This comment critiques their revision from a theoretical perspective and additionally questions the methodology reported by the authors to establish the RCAT's validity. We conclude that the Russell and Levy modifications of the CAT make the RCAT a new, different, and as yet unvalidated instrument. Suggestions are offered for future research in the area of modifying the CAT or its scoring system.