A slide people get
Lesson 11 of 13 in the course “AI Images and Slides”. Free, with animations and a quiz.
Words plus a picture
Psychologist Richard Mayer spent decades testing in experiments how people learn from slides and screens. His first finding: words together with a fitting picture are understood better than words alone. That’s the multimedia principle. But “fitting” is the key word. A diagram of how a candle works helps. A chart of sales growth helps. A random pretty picture doesn’t, and more on that next.
Don’t read the slide aloud
The most recognisable mistake: a paragraph on the slide, and the speaker reads it out. The room reads faster than you talk and is already bored. Mayer calls this the redundancy principle: when the same text is both on screen and spoken next to a diagram, people understand less. Better: a diagram and 3–6 words on the slide, with the explanation in your own voice. AI tools love long paragraphs, so cut them boldly.
Decorative pictures get in the way
Generators make a picture for any slide in seconds, and it’s tempting to decorate every one. But research by Mayer and colleagues shows that interesting but unnecessary details distract and hurt understanding. They’re even called “seductive details”. The coherence principle says: remove everything that doesn’t help the main idea. A candle picture with “wax” and “wick” labels explains. An abstract neon candle just takes up space.
Highlight the key point
The signalling principle: show the eyes where to look. Liya’s sales chart has four bars, but one matters: December. If all the bars are the same colour, the viewer hunts for the meaning and may not find it. If December is bright, the rest grey, and the caption says straight out “2.5 times more in December”, the idea lands in a second. Ask AI: “highlight one key element in colour and make the rest grey”.
10 slides, 20 minutes, 30 points
Guy Kawasaki, a venture investor and former Apple evangelist, proposed a simple rule for pitches: 10 slides, 20 minutes, font no smaller than 30 points. It’s not a law of nature, it’s a rule of thumb, but it cures overload brilliantly. A large font physically won’t let you cram in a paragraph, and 20 minutes leave time for questions. For her class Liya squeezed it even more: 7 slides, 7 minutes.
The final check
Before your talk, run through the checklist. Titles are takeaways, and they tell the story. Every number has a link. Every picture explains something. The font is readable from the back row. And two rehearsals out loud with a timer. You can also ask AI to play a strict teacher and tear your deck apart before the talk, not after. The prompt is below.
Check yourself
- There’s a paragraph on the slide and Liya plans to read it out. What’s better?
Correct answer: Keep a diagram and 3–6 words and explain by voice. The same text on screen and by voice gets in the way: that’s the redundancy principle. - Liya wants a pretty AI image on every slide. What does Mayer’s research say?
Correct answer: Extra details distract: a picture should explain. That’s the coherence principle: remove whatever doesn’t help the main idea. - How do you make people see the key point on a chart at once?
Correct answer: Highlight the key element in colour, grey the rest, and caption the takeaway. The signalling principle: show the eyes where to look, and the idea lands in a second.