We make assumptions all the time, about everyone. Mostly, we assume people are like us, share our beliefs, our interests, our tastes, our background, our likes and dislikes, and our sense of humor.
Just the other day, I wrote about assuming an audience member is adversarial based on a challenging question. Frequently, we assume the audience understands our big words, jargon and acronyms, so it doesn't occur to us to explain them (the "curse of knowledge").
We assume the audience knows less than they do, therefore treating them like children. Or we assume they know more than they do, therefore causing them to retreat into their shells and disengage.
We assume they're judging us, out to get us, or would enjoy seeing us fail. Or we assume they worship us, think we're brilliant or find us hilarious.
All of these assumptions prevent connection and create a barrier of misunderstanding between the speaker and the audience. Some are minor, where we assume everyone watches football, and then the sports analogies fall flat.
Some are major, where we assume everyone shares our sense of humor, and then half the audience is offended by a seemingly harmless joke.
It's difficult, to say the least, to try to appease everyone and still give a presentation that is informative, engaging, and has the stamp of your own personality and style. And it's not possible to please or appease everyone, anyway.
However, you can find out as much about your audience as possible before you speak. This is a trusty old rule, handed down from the beginning of time, but one that is frequently ignored.
As I've mentioned in several posts on preparation, learning about your audience in advance can partially protect you against making these kinds of mistakes. Nothing can truly protect you against missing the mark or offending someone, unless your presentation is so bland and inoffensive that it makes no impact at all.
But the first step is in dropping your assumptions that everyone is like you and making an effort to find out who they really are.
What assumptions have you made about audience members?