I can't seem to find the post, but I recall at one point that I wrote something about the ability to paint pictures and hear sounds and music in one's mind, and what life would be like if we didn't have that amazing capability. I wrote something about the brain being a theatre in which we controlled every actor, every voice, and every note in the soundtrack. In writing that, I think it was the first time that I really thought about how amazing it is that we can synthesize even a smell or the feeling of touching a certain fabric with a high degree of precision.
So today, I learned that out that this capability actually isn't universal. That such people exist who cannot visualize images and synthesize sounds in their minds. It's a fascinating read, even moreso given that the author is in fact a highly intelligent and successful software engineer and entrepreneur, one of the founders of the Mozilla Firefox project and other major internet cornerstones.