Color Blindness: I followed a link from Synthetic Morpheme to a site with a bunch of tests for color blindness. These are really interesting. It's hard, if not impossible, to visualize the perceptual experiences of someone who physically doesn't percieve what you do. I was especially interested by a test in which people without color blindness see nothing, and people with total color blindness see nothing. But people with red-green color blindness see the number '5'. I played with the color levels in Gimp, and the results below are the original, a grayscale version, and a version with the reds and greens merged together: [raises an eyebrow] Fascinating.