[magneticnorth]

This is a great question. Personally, I have very low mental-image ability. I think I realized that this is a thing when a friend was genuinely grieving that he was losing the ability to visualize his mother's face aside from picturing photos he has. My mother is alive and well but I have never been able to literally visualize her face, or anyone's.

Similarly, I've known people who are problematically unaware of smell and particularly their own body odor. I know it's supposed to be a thing that you become to used to your own smell, but I've known more than one person who simply never realized that they, or anyone really, can be smelled by other people.