According to estimates from the Howard Hughes Medical Institute, somewhere around 7% of men and 0.4% of women are color blind. The most common is red-green color blindness. I always wondered whether the presentation rule of “never use red” in a presentation was true. So, I spent the a few hours on the website www.vischeck.com to find out.

Vischeck.com lets you upload images to see how they would appear with different types of color blindness.

So, we can’t tell yellows from reds and greens, but we can still see the BOLD effect in the words clearly.

I decided to try a few of my own slides to see how they project:

These first two are from a lecture I developed before abandoning red altogether. I was very disappointed to find out my orange (2nd pic) suffered the same fate as red.

Here is the effect in some of my more recent slides.

So, the morale of the story is that it is likely better to just avoid red altogether, as well as green. However, they can be used with the following caveats:

1. Do not try to contrast reds, yellows, and greens because they all look the same
2. Consider using bold, italics, or other effects to give emphasis in addition to the color
3. Used in isolation, a red or a green will appear yellow to a small portion of your audience. It will still stand out, just not the way you intended
4. Checking your slides at a site like www.vischeck.com will avoid creating presentations that inadvertently diminish the learning of a portion of your audience

References:

Howard Hughes Medical Institute (2005). Seeing, Hearing, and Smelling the World/Breaking the Code of Color: Color Blindness: More Prevalent Among Males. http://www.hhmi.org/senses/b130.html

Another possible myth of presentation design is that the magic number for retention is:

7 +/- 2

It appears that the actual magical number is closer to 4.

A psychologist by the name of Alan Baddeley dug up the number ofter quote from the research paper by George Miller and actually found that it was a talk from a professional meeting, not research!

Baddeley did his own studies to support the number 4 as the true “magic” number for memory and information processing. However, this has not been studied extensively in medical education, especially with the ideas of organizing and anchoring.

So, for now, we can try to build our presentations around the number 4, but may be able to stretch this much further when other educational principles are applied.

References:

Miller, G. (1956) “The magical number seven plus or minus two: Some limits on our capacity for processing information.” Psychological Review. 63:81-97

Baddeley A. (1994) “The magic number seven: Still magic after all these years?” Psychological Review. 101:353-6