"Rhetorical Ability": Reason, Emotion, and Character as Heuristics for the Evaluation of Efficacy in Design

Usability inspection is a major standard for design evaluation in which expert evaluators use heuristics to assess efficiency and quality. However, usability alone is insufficient to assess efficacy in design problems in which the main design goal is not cognitive interaction. For example, goals such as social change (e.g. health promotion), communication, or entertainment, in the field of product and system design, require design evaluation that goes beyond usability. In this paper we argue that rhetorical ability (or rhetorability) is a plausible heuristic evaluation approach in the field of design for social change. We propose nine heuristics based on the three rhetorical appeals, logos (reason), pathos (emotion), and ethos (credibility). The applicability of the method depends on the understanding of the rhetorical situation; thus, the rhetorical ability heuristic evaluator should be an expert in the audience needs, the design goal, and the design problem.