Cognitive research indicates that science experts commonly use diagrams as mediational tools for reasoning visually. But in science education materials and practices, visuals are typically "aids" rather than fundamental representations. This research will examine how students learn to comprehend, use, and construct diagrams as thinking tools. It will focus on the diagram-dense field of beginning optics. The project has two interacting phases: research on how students understand static optics diagrams, and development and refinement of prototype computer- based dynamic diagrams and diagramming tools. Specific tasks are: (1) Pilot research, and analysis of diagrams in optics texts, (2) research on instructional practices with these diagrams, (3) research on student understanding and use of diagrams, (4) design and develop interactive diagrams and a dynamic diagram-construction kit, (5) carry out research with prototypes, and (6) formulate and disseminate implications for creation and use of interactive diagrams in science education. Such research on visual education in science will help guide development of new curricula and software for science education. The project team of cognitive scientists, science educators, graphics specialists, and systems developers is devoted to promoting learning and reasoning in science with new data, theory, and innovative prototypes of dynamic diagrams. These interdisciplinary activities more directly link science education research, materials development, and classroom activities. Cost sharing is provided by the Institute for Research on Learning which is contributing indirect costs and APPEL which is contributing four MacIntosh II systems.