If you put your left hand into a bucket of cold water, and your right into hot water, and then plunge them both into a single bucket of room-temperature water, a funny thing will happen. Your sensations will reverse: your left hand will feel warm and your right hand will feel cold. There’s no magic in it, it’s simply the contrast between the starting and ending points of each that makes the difference.
In a similar way, the contrast between your start and end points in a presentation or sales call can make all the difference between success and failure.
Contrast is important for two reasons: it can create attention and it can affect the perception of the facts.
In her excellent book, Resonate, Nancy Duarte tells us that “People are naturally drawn to contrast because life is surrounded by it.” She then adds, “Your job as a communicator is to create and resolve tension through contrast.” The difference between contrasting ideas generates interest like the opposite poles of a battery generate electricity.
As the bucket example demonstrates, contrast also affects how a situation or a fact is perceived. There is very little that is purely objective; even a precisely measurable number such as temperature can feel subjectively different depending on how it is perceived in relation to a different temperature. Colors can look lighter or darker depending on background, etc. If contrast can work so powerfully for things we can directly see and feel, imagine how much more it can do for less tangible things such as opinions and interpretations.
Effective communicators achieve contrast in two ways: through their content and their delivery.
You can create contrast in the content of your presentation through its structure. One way is by making your entire presentation a story. Stories are all about contrast—there is usually a conflict between what the protagonist wants and what is happening right now. The conflict keeps us tuned in, and the resolution is all the more satisfying the greater the conflict. For many business presentations, the problem/solution structure is an excellent way to contrast the pain of the existing problem with the pleasure to be gained from your solution. The yesterday-today-tomorrow structure provides forward flow by contrasting what is with what could be.
Another way is to structure your presentation with contrasting data types. I saw one such example just this morning in a presentations class I taught in India. The presenter used bold visuals to highlight the fact that a problem existed, then threw in a slide which contained several graphs that made his emotional appeal credible. He did this several times in succession, and the contrast between highly visual and emotional slides and coldly logical ones kept the audience riveted.
Contrast can be exploited even within individual sentences. Kennedy’s inaugural address would have been long forgotten if he had merely urged Americans to do more volunteering. It’s long remembered because of his use of contrast:
“Ask not what your country can do for you—ask what you can do for your country.”
Even individual facts can be contrasted, such as when you contrast the price of your solution with the cost to the client if their current situation is not resolved. Numbers have meaning only in comparison to other numbers, and as a presenter you get to choose the comparison.
You can also maintain attention through contrasts in your delivery. One of the most obvious ways is by varying aspects of your voice. People who normally speak fast may want to slow down to emphasize a particular point, or to pause occasionally to let the audience digest what they’re saying. You can raise your voice to highlight something important, although sometimes lowering your voice to a point that is just barely audible can make a dramatic contrast with what has gone before and really get people to sit up straight and listen. Once in a while, why not move from one side of the room to the other as you switch from one point to the next?
 The technical term for this is chiasmus, for those who are interested.