What we pay attention to is profoundly influenced by our memory. Experiences we’ve had so far predict when we should be paying attention. Culture matters too. Whether in business or in school, these differences can greatly affect how an audience perceives a given presentation. We pay attention to things like emotions, threats and sex. Regardless of who you are, the brain pays a great deal of attention to these questions: Can I eat it? Will it eat me? Can I mate with it? Will it mate with me? Have I seen it before?
If you surprise your audience you can be sure that you will have their attention. After certain amount of time, disappointing to teachers and Powerpoint- or Keynote-presenters everywhere, audience‘s attention drops dramatically. You must come up with something emotionally relevant at least every ten minutes to regain their attention.
Source: Brain Rules by John Medina (www.brainrules.net)