Let me give you an example of how bad human working memory is. You're at a tube station and you see the train coming and you have purchased a ticket. You see the ticket. Car 5 seat 42. "Got it!" you say. But have you? You have absolutely no idea where you're gonna sit, do you? You will see your tickets at least 6 times before you find your seat.

The only bad news in this is that you do not have a separate working memory for train tickets, and a separate working memory for powerpoint presentations. We use the same disappointing working memory for both these activities.

So, how can you improve your powerpoint slides to maximize the chances of your message to get across? There are principles to cognitively and psychologically improve and optimize your keynotes slides.

One message per slide

Why should we have 1 message per slide? Humans can only focus on one thing at a time. Have you ever been in a situation when someone is talking with you and you hear your name from across the corner, and the person you were talking to said, "well don't you agree" and you have no idea what to agree with? We've all been in this situation.

Human brain can get easily distracted, and to make it simple for our presentations, it is important to discuss one message per slide. A message that you want your audience to remember. We are extremely limited to understanding more.

Redundancy effect

This equation "+ =" is called redundancy effect. It works like this. If you have text sentences on your keynotes and you persist with the annoying idea of speaking at the same time, what will be remembered by the audience is (1+1=0) zero. (or very close to zero). You can't put text sentences on your powerpoint and speak at the same time.

You must use your slides for what they are supposed to be used for. Short sweet bit of text, with a supporting image. Create a message.


Before going further, I want to make you aware of something and it is the following. Everytime you open your eyes for the rest of your life, you will focus on four (4) things.

  1. Moving objects
  2. Signaling colors (like red, orange and yellow)
  3. Contrast rich objects, and
  4. Big objects.

To give you a practical example of that, I want you to imagine being home with a really good friend, now the television is on but the sound is off, you are having a great conversation, but do you find it easy to not look at the television? No! why not? because it got moving objects, it got signaling colors, it is high in contrast and tv's come in really big sizes these days. So why not use this to our benefits?

Most important point of your slide gets the biggest size.

It is interesting to note that every keynotes template is built in a way that the headings are usually big and the content is small, however, how many times the headline is the most important point of the slide? Very rarely. Going absolute opposite to our biological reactions. Don't follow the templates!


Contrast controls your focus. To convey many points per slide, use the principle of contrast, in which you highlight the point you're talking about, and dim the point that you aren't.

With the principle of contrast you can show a tremendous amount of data (example, big tables) without having your audience be all over the place, without understanding any of it.

White background has the highest contrast. Don't use it. It takes away the focus from the point you're making and to the screen. Power points are not supposed to have white background. If you have a dark background people focus on you. Why is that important? because you were, you are and you always will be the presentation. keynotes are just your visual aid.


This is the most important principle. The more objects on your slide, the harder for people to make sense of what you are talking about. If you have more than 6 objects on your slide it takes 500% longer time and 500% more energy to process that information. This is because our mind sees things if they are in smaller numbers, but counts if they are in higher numbers.

The magical number is 6. If you have more than 6 objects on a slide, the people in your audience will takes 500% more energy and cognitive resources to understand what is in your slide. Which you surely do not want.

The amount of slides in your keynotes has never been the problem. It is the amount of objects per slide which has been the problem. The stupid idea in the corporate world has been to limit the slides from 40 to 4. So what do people do? Well they take the content from the rest of the 36 and jam in the first 4. Isn't that counter productive?


One message with highlighted contrast and size with minimum sentences on a dark background with no more than six objects per slide.

Thanks to David JP Phillips for his amazing presentation on the topic