Message Generalizations That Support Evidence-Based Persuasive Message Design: Specifying the Evidentiary Requirements

Evidence-based persuasive message design can be informed by dependable research-based generalizations about the relative persuasiveness of alternative message-design options. Five propositions are offered as specifying what constitutes the best evidence to underwrite such generalizations: (1) The evidence should take the form of replicated randomized trials in which message features are varied. (2) Results should be described in terms of effect sizes and confidence intervals, not statistical significance. (3) The results should be synthesized using random-effects meta-analytic procedures. (4) The analysis should treat attitudinal, intention, and behavioral assessments as yielding equivalent indices of relative persuasiveness. (5) The replications included in research syntheses should not be limited to published studies or to English-language studies.