To control for interactions in learning research due to subjects' prior knowledge of the instructional material presented, an imaginary curriculum was presented with a computer assisted technique based on Carl Berieter's imaginary science of Xenograde systems. The curriculum consisted of a classification system for ten conceptual classes of fictitious planets. The computer system, written in Apple PASCAL, presented three types of displays: (1) definition of the concept's attributes and classes; (2) instance selection and presentation, which allowed trainees to explore the classification system in a hierarchical or tabular format; and (3) a test of concept acquisition. The instruction was presented within a science fiction context; the first screen welcomed subjects to the Starcruiser Academy Science Officer Training Course. Subjects in the first study were 38 high school students. The treatment group, who received advice on selecting pairs of examples to maximize learning, scored moderately higher than the control group. In a second experiment, undergraduate education majors were exposed to either hierarchical presentation of materials, matrix or tabular presentation, or a combination of both. Results strongly favored the hierarchy-only approach. (Extensive appendices include a number of the presented screens and instructions accompanying the classification test). (GDC)