Speaker: Ralph Lengler, University of Sydney.  Moderator: Nick Seaver, MIT. Abstract: Some visualizations need not only adequately represent information; their presentation needs also to be effective, leading to a behavior change in the viewer. Rhetorical figures, like metaphors, are said to increase the effectiveness of a message. The power of rhetorical figures stem from their potential in creating meaning in the recipient because they adhere to a predefined template (Phillips & McQuarrie 2004). This paper first presents an overview of published empirical studies on why rhetorical figures are more persuasive. Second it presents a definition of the rhetorical figures visual antithesis and visual metaphor. A visual antithesis is a juxtapose of two similar pictures which are contrasted in order to stimulate the viewer to draw inferences, e.g. in Al Gore’s An Inconvenient Truth (2006) where photos of a glacier 70 years ago and the present are contrasted. In a more information visualization centric context, Barack Obama just recently used a visual antithesis (see link) to communicate his economic achievements fighting the recession. Third, it explains how those figures are most effectively used for visual argumentation purposes and how certain shape-based presentation forms like in Obama's case increase its effectiveness. Fourth it presents some preliminary empirical results and outlines future research.