How Cognitive Science Can Improve Your PowerPoint Presentations:
Harvard cognitive scientist Stephen M. Kosslyn, who studies how brains process images, explains that the four rules of PowerPoint are: The Goldilocks Rule, The Rudolph Rule, The Rule of Four, and the Birds of a Feather Rule.

[UPDATE 24 JAN 08] Featured in BoingBoing

• The Goldilocks Rule refers to presenting the « just right » amount of data. Never include more information than your audience needs in a visual image.
• The Rudolph Rule refers to simple ways you can make information stand out and guide your audience to important details — the way Rudolph the reindeer’s red nose stood out from the other reindeers’ and led them. If you’re presenting a piece of relevant data in a list, why not make the data of interest a different color from the list? Or circle it in red? « The human brain is a difference detector, »
• The Rule of Four grows out of the fact that the brain can generally hold only four pieces of visual information simultaneously. Never give more than four pieces of information at once. It’s not that people can’t think beyond four ideas — it’s that when we take in the visual information on a slide we start to get overwhelmed when we reach four items.
• The Rule of Four is a simple but powerful tool that grows out of the fact that the brain can generally hold only four pieces of visual information simultaneously. So don’t ever present your audience with more than four things at once. This is a really important piece of information for people who tend to pack their PowerPoint slides with dense reams of data. Never give more than four pieces of information at once. It’s not that people can’t think beyond four ideas — it’s that when we take in the visual information on a slide we start to get overwhelmed when we reach four items.