Simplicity, or more precisely the cognitive fluency, increases persuasion. But does it also mean that vividness and persuasion are incompatible because vivid details usually reduce cognitive fluency? Is the shorter message always more persuasive? Or is it possible that a more detailed and vivid message (which can be also more difficult to process) can be more persuasive? The short answer: it depends.
Vividness and Trivial Persuasion
Most people assume that vividness should help to make an idea more memorable and believable. And there are several studies that support this view. In fact, even trivial details can increase believability. In a 1986 study by Jonathan Shedler and Melvin Manis, mock jurors listened to a tape recording of a child custody case (“Can the Availability Heuristic Explain Vividness Effects?”, Journal of Personality and Social Psychology, 51, 26-36 (1986)).The jurors had to decide whether Mrs. Johnson was fit as a mother. Some subjects heard pallid arguments, while others heard the same information with colorful details. For example, a pallid version of a favorable argument said that, “Mrs. Johnson sees to it that her child washes and brushes his teeth before bedtime.” The colorful version also added that the boy “uses a Star Wars toothbrush that looks like Darth Vader.” Of course, Mrs. Johnson is no better mother just because her son uses the Star Wars toothbrush instead of a generic one (though Star Wars fans might disagree on this one), but the judgments were more favorable when the subjects heard the colorful details.
To vivify or not to vivify?
So the study described above seems to suggest that vivid messages are always more persuasive. Does it mean that we should always jazz up our messages with vivid details if we want to persuade more? Well, this is not as simple as it appears. Other experiments showed that vividness can be ineffective at best and sometimes undercut the effectiveness of your message altogether.
Research on vividness has shown that there are three basic rules we must follow for vividness to work in our favor.
I. People Have to Pay Enough Attention
One study found that vivid messages were less effective than pallid ones when the subjects paid little attention to the message. As the authors of the study explained, colorful language and picturesque examples interfered with the essential meaning of the message and so reduced its persuasiveness.
When the study subjects paid enough attention to the message, vividness didn’t reduce effectiveness. Most likely this study found no positive effects because it neglected two other rules.
II. Vivid Elements Must be Congruent with the Essence of the Message
Another study also found that vividness can reduce persuasiveness, but this was true only when vivid elements were incongruent with the theme of the message. When vivid elements matched the essential theme, the message was more persuasive.
It explains in part why some PowerPoint presentations abound with rich images can backfire. Many presenters now follow the advice to get rid of text and embellish slides with plenty of images. Sadly, often such images only vaguely match the central message of the presentation. This incongruence between the essential message and images will usually backfire.
III. Vivify Only Central Elements of Your Message
One of the most recent studies likewise revealed that vividness can help or hinder depending on how it’s used. The study authors tested vividness in two ways: (1) vividness of only central elements of the message, or (2) vividness of the central elements and other portions or only other portions. They found that vividness increased persuasiveness when only the central elements were vivified. As the authors cautioned, increasing overall message vividness is likely to backfire.
Summary: When Vividness Boosts Memorability and Believability
First, make sure that people pay enough attention; if they don’t, you’re better off using concise and colorless descriptions. Second, if you want power up your message with vivid elements, focus only on central elements of your message, i.e. your thesis. Finally, use colorful language or other vivid details only if it is congruent with your message (i.e. matches its essence). (That also means that you should probably leave out a clip-art of shaking hands in your presentation about the margins of the last quarter.)