Concept mapping is a useful tool to probe changes in each student\u27s understanding of science concepts, but it is weak in grasping visually changes in their understanding as group or class. To compensate for its weak point, we devised a way of deriving hierarchical digraphs, using the ISM method, from concept maps constructed by learners in science instruction. From the digraphs obtained before and after instruction in three units, it was found that our way could provide teachers with valuable information in day-to-day science instruction
