Principle 7 - Tell and Show

The human voice is the best instrument for communicating complex information to other humans. So, your talk will go best if the humans in the audience actually hear what you say. I have so far given advice about how to help the audience focus on what you are saying, by removing words from slides and by using black slides to help the audience focus on your words. This new principle, "Tell and Show", provides some relatively subtle advice about how to guide the audience through your work. 

I commonly observe that speakers click on a slide and then proceed to walk the audience through the contents of the slide. For example, they might say something like "As you can see in this slide, the length of the wombat's nose is correlated with the the length of their toenails." It is usually more effective to do this in reverse. First, say "Because of everything I have just told you, we wondered if there might be a correlation between the wombat's nose and their toenails. So, we measured 50 wombat's and this is what we found." Hopefully you said this while there was no distracting slide in the background (use black slides). Click to the data slide, explain the axes and describe the result. "As you can see, we plotted wombat nose lengths on the X axis and wombat toenail lengths on the Y axis and we observed a remarkably strong correlation between these traits."

One obvious advantage of tell and show is that you end up telling the audience about each point twice. They hear the result once before they see the data and then again when they are looking at the data. This helps guide them toward the relevant observation in the data and increases the likelihood that they will remember the result after you move on to your next point. 

A more subtle advantage of tell and show is that it forces you to focus on one result at a time and devote one full slide to each result. This will help clean up the appearance of your slides. "Tell and show" also weakens the argument that you should put words on slides to remind the audience what the slide is about. With tell and show, you introduce the theme of the next data slide before you show the data, which is far more effective than putting words on slides, which end up distracting the audience from the data.