Why ask why?: considering motivation in visualization evaluation

My position is that improving evaluation for visualization requires more than developing more sophisticated evaluation methods. It also requires improving the efficacy of evaluations, which involves issues such as how evaluations are applied, reported, and assessed. Considering the motivations for evaluation in visualization offers a way to explore these issues, but it requires us to develop a vocabulary for discussion. This paper proposes some initial terminology for discussing the motivations of evaluation. Specifically, the scales of actionability and persuasiveness can provide a framework for understanding the motivations of evaluation, and how these relate to the interests of various stakeholders in visualizations. It can help keep issues such as audience, reporting and assessment in focus as evaluation expands to new methods.