Every presentation has two sides. You're speaking, but your audience is listening. If you want to give a great presentation, you need to know about people. The more you understand about how people think, learn, hear, see, react, and decide, the better you'll be able to put together a presentation that informs, inspires, and motivates.
Following are five facts that great presenters know about people.
Fact 1: People learn best in 20-minute chunks.
When I'm coaching and mentoring people in presentations, I tell them to watch TED talks—short presentations by people accomplished in their fields. Interestingly, most TED talks are 20 minutes long. I think that's one reason they're so effective. These same presentations stretched out to an hour might not seem so brilliant.
In 2012, Maureen Murphy tested the idea that 20 minutes is the right amount of time for a presentation.  She had adults attend a 60-minute presentation, and then the same presentation broken up into 20-minute chunks. She wanted to see whether people's memory of the talk and reactions to the talk would differ based on the time of the presentation. When the presentation was chunked into 20-minute segments, people enjoyed the presentation more, learned more, and retained the information longer.
Most of us give presentations that are longer than 20 minutes. If your presentation is longer, see whether you can build in some kind of change every 20 minutes—take a break or a short stretch break, or include an activity or an exercise.
Fact 2: Multiple sensory channels compete with each other.
During a presentation, two sensory channels are the most active: visual and auditory. Your audience is looking at you and listening to you. They might also be looking at slides or other visual elements you're showing. If the slides are easy to understand, such as photos or diagrams that add extra context and meaning, these multiple channels are a positive experience for the audience. But if the slides are hard to read, complicated, or contain a lot of text, the visual channel is distracting—and visual trumps auditory. Humans are very visual creatures. When you present complicated information for people to read or view, they're not listening to you anymore.
In particular, text-filled slides combined with a speaker who's talking is just a bad sensory combination. If people are reading, they're not listening. You don't have to use slides in a presentation. First try putting together your presentation without any slides, and then decide whether any of your points would be enhanced by the use of a visual example or illustration.
You know what I call slides with a lot of text on them? Your notes! If you feel you need slides with text, it's probably because you feel you need notes—but you don't have to show the audience your notes.
Fact 3: What you say is only part of your message.
Psychological research over the last 15 years has revealed that people process information unconsciously, and they make very quick—one second or less—unconscious decisions about other people. People react not only to your message, but to your voice, stance, facial expressions, and hand movements. A special field called paralinguistics studies how information is communicated in addition to the words you say. Suppose I say, "I'd love to go to the store with you" with enthusiasm and excitement in my voice, or I say the same words with annoyance. The words might be the same, but the paralinguistics of the message are totally different. Think about how you're saying something—not just the words. A great trick is to record a video of yourself giving your presentation; see what your body language says, and notice what your paralinguistics say.
Fact 4: If you want people to act, call them to action.
I attended a fundraiser recently at which the speaker gave a pretty good speech (though I think he could have used a speech coach). But he didn't have a call to action at the end of his speech. He was trying to raise funds, but he didn't ask for the money at the end of the presentation. People were walking around after the presentation with jars to take donations, but no one had actually asked for the money. At the end of your presentation, be very specific about exactly what you want your audience to do.
Fact 5: People echo your emotions and feelings.
People imitate what they see. If you're smiling, they tend to smile; if you're energetic, they're energetic. When you're passionate about your topic, your audience usually will be passionate. People like to watch and listen to speakers who are animated and excited about their topic. If your topic excites you, don't hold back—show how you feel! That feeling will be contagious.
So there you have it! Five things you need to know about people in order to give a better presentation. If you're interested in more ideas like this, check out my book 100 Things Every Presenter Needs To Know About People.
 Maureen Murphy, "Improving learner reaction, learning score, and knowledge retention through the chunking process in corporate training." University of North Texas Digital Library, 2012.