When you want to effectively use reasons and evidence underlying your position, should you articulate them explicitly or implicitly? One might argue that implicit reasons should engage the audience more, and engaged audience is a good thing for persuaders.
A meta-study by Daniel O’Keefe examined three aspects of articulation explicitness:
- Information-source citation, i.e. whether the persuader cites the source which supports the argument
- Explicit articulation of the premises
- Quantitative specificity, e.g. saying “85% of respondents support …” as opposed to “most respondents support …”
The study found that explicit arguments “are significantly more credible and significantly more persuasive” than implicit ones. This is especially the case with information-source citation and argument completeness. The meta-study found little support that quantitative specificity is more effective, but this could be due to the small number of cases which tested quantitative specificity.
So we can use these research findings in two basic ways.
First, whenever possible, clearly cite the source for your arguments. It may be statistics, an authority on the issue, etc.
Second, complete syllogisms will be more persuasive than enthymemes.
A complete syllogism is a three-part argument; it spells out its premises and conclusion explicitly:
- All humans are mortal.
- Socrates is human.
- Therefore, Socrates is mortal.
An enthymeme is an abridged syllogism, which implies a premise (or sometimes a conclusion) but does not explicitly spell it out: “Socrates is mortal because he’s human”
Finally, it might be worth citing specific numbers even though the meta-study found no significant effects. One reason is that specific numbers, especially unexpected numbers, might work through some mechanisms (e.g. unexpectedness and increased cognitive elaboration) that were not accounted for in the meta-study and the studies it drew on.
- O’Keefe D. J. (1998). Justification Explicitness and Persuasive Effects: A Meta-Analytic Review of the Effects of Varying Support Articulation in Persuasion Messages. Argumentation and Advocacy, 35, 61-75 (1998).