In The Science of Speaking, I repeatedly talk about the importance of making sure all aspects of your speech are congruent: your message vocal tone, facial expressions, and visuals should all support each other, rather than fighting against each other.
While ensuring this kind of congruence is essential, studies have shown that—when used well—contrast can also be effective. For example, in a classic study at Haverford College, congruent or contrasting music was played either before or during a film clip. As expected, when the background music during a clip was congruent, participants remembered the clip better than when it was contrasting. But when the music was played before the clip, contrasting music led to better recall. This is because the contrast between the film and preceding music made the film stand out more.
Therefore, while congruence is essential to consider when trying to make your presentation cohesive, it’s also important to consider how you can use the power of contrast to make your important points stand out in your presentation, and furthermore, how you can make your presentation stand out in people’s minds compared to everything else they’ve seen.