In an effort to create a mathematics learning environment in which the social nature of the classroom facilitates conceptual conjecture and justification, a visual representation has been designed that students can manipulate to make demonstrative proofs in the domain of proportional representation. This study explores student use, incorporation, and extension of this representation in classroom and face-to-face settings. Subjects were 49 high-ability sixth graders using the video-based mathematics series, the Jasper Adventure Series. The visualization helped students identify and articulate proportional relationships. Students used the representation in diverse and often innovative ways when they demonstrated their problem solutions to other students. While students were able to understand refutations of problems, they generally could not generate them, although the visual representation helped them generate contradictions in reasoning. Students began to create a culture in which demonstration became a social phenomenon. Results suggest a promising model of discourse that is an alternate to the procedural descriptions language in general use. Four figures illustrate the study. (Contains 5 references.) (SLD)