It's no surprise that including the unexpected in your presentation is an excellent way to keep your audience engaged.What may be more surprising however, is that surprises actually help your listeners retain information.
Check out this University of Cambridge study:
Because they are hard to forget, surprises can help us learn.
Now scientists have identified a part of the brain that may be involved in learning from surprises. A team led by Dr. Paul C. Fletcher at the University of Cambridge monitored the brain activity in a group of volunteers who were participating in a simulation exercise.
The participants pretended to work at drug companies and were asked to predict whether a particular fictitious drug would trigger a particular fictitious syndrome.
In the early phase of the study, when the participants were not familiar with the effects of the various drugs, imaging tests detected high levels of activity in this part of the brain.
As the volunteers became familiar with the effects of the drugs, so that they were no longer surprised by the results, activity in the dorsolateral prefrontal cortex declined, but later in the study, this region became more active when the participants were surprised by unexpected responses.
- Published in Nature Neuroscience, 2001
From the Green Room: Don't give away your message. Your audience will be much more likely to remember it if it takes them by surprise.

