In the cognitive test interpretation literature, a Rational/Intuitive, Indirect Empirical, or Combined approach is typically used to construct conceptual taxonomies of the functional (behavioral) similarities between subtests. To address shortcomings of these approaches, the functional requirements for 49 subtests from six individually administered scales of cognitive ability (WISC-IV, WPPSI-III, SB-V, WJ-III, CAS, and UNIT) were typed on index cards. Forty-eight (48) in-service and/or pre-service school psychologists were asked to sort the cards into two, three, five, or eight functionally similar piles. A multidimensional scaling analysis was performed on a 49x49 matrix of similarity scores collapsed across all 48 subjects. Three dimensions were extracted from the data: "Reproduction of Stimuli Sequences versus Picture Viewing" (Dimension 1), "Timed Speed versus Untimed Power" (Dimension 2), and "Verbal versus Performance" (Dimension 3). A hierarchical clustering procedure was then applied to the matrix data, and results were compared to previous categorization schemes identified in the test interpretation literature.