Persuasion is more effective when you use the "unexpected message" and back it up with strong arguments. Why? People will listen and pay more attention to your message if you had and unexpected element to it. The problem is if you don't deliver something worthwhile the persuasion is lost. Swaycraft Persuasion Techniques discusses the surprise element for effective persuasion.
"In consumer research at least, experts can be more persuasive when they express uncertainty. Uncertainty works here because it is unexpected: we expect experts to be certain about their position because of their specialized knowledge and training."
"Many authors suggest unexpectedness as one of the persuasion cornerstones. For example, Heath brothers make unexpectedness second element in their SUCCESs formula. (SUCCESs stands for Simple, Unexpected, Concrete, Credible, Emotional, Story – see their bestselling Made to Stick)."
"Overall, this is solid advice. But it can also backfire."
"Research indeed shows that in general unexpectedness boosts persuasion. The reason: unexpected message surprises your audience; they pay more attention; the more attention they pay the more likely it is that the message will sway them."
"In essence, people are more likely to meditate on your message if it surprises them.
"But here is a critical requirement: your message must be supported by strong arguments. If not, your message will be ineffective or will even backfire because your audience will be more likely to spot any flaws."
- Richard E. Petty, John T. Cacioppo, Rachel Goldman, “Personal Involvement as a Determinant of Argument-Based Persuasion,” Journal of Personality and Social Psychology, Vol. 41, 847-55 (1981).
- Richard E. Petty and John T. Cacioppo, Communication and Persuasion: Central and Peripheral Routes to Persuasion (1986)