This study concerns the learning of scientific subject matter. In general, previous research on learning has been based on a two element paradigm of instruction affecting performance, but the paradigm used here emphasizes the importance of memory as a mediator between instruction and performance. Gagne and White postulated four types of structures in memory: propositions, intellectual skills, images, episodes. The existence of these structures and their relationship with performance was investigated. An individual' s preferred way of dealing with cognitive tasks over time on an imagery verbal dimension was also investigated. Instruction was presented by using five program booklets. The two science experiments were either carried out by students in small groups or demonstrated by the class teacher. Instruction was administered by two science teachers responsible for four unstreamed Year 10 classes in a metropolitan state coeducational high school. Each teacher taught two classes that were randomly assigned to either the small group or teacher demonstration treatment. The sample comprised a total of 78 students. Interviews were conducted by seven interviewers.