Want to learn more about what's going on inside your own head? Check out Brain Rules: 12 Principles for Surviving and Thriving at Work, Home and School by John Medina. The site (linked to above) has lots of pretty cool, short videos explaining why our brains work the way they do. Working for XPLANE, I especially liked Rule # 10: Vision Trumps All Other Senses, and it contains this rule of thumb for presenters:

You'll get 3x better recall for visual information than for oral. And you'll get 6x better recall for information that's simultaneously oral and visual.

Here's why:

• We are incredible at remembering pictures. Hear a piece ofinformation, and three days later you'll remember 10% of it. Add apicture and you'll remember 65%.
• Pictures beat text as well, in part because reading is soinefficient for us. Our brain sees words as lots of tiny pictures, andwe have to identify certain features in the letters to be able to readthem. That takes time.
• Why is vision such a big deal to us? Perhaps because it's how we'vealways apprehended major threats, food supplies and reproductiveopportunity.
• Toss your PowerPoint presentations. It’s text-based (nearly 40words per slide), with six hierarchical levels of chapters andsubheads—all words. Professionals everywhere need to know about theincredible inefficiency of text-based information and the incredibleeffects of images. Burn your current PowerPoint presentations and makenew ones.

Wow!