Blake Ross discovers he is aphantasic (HN) as is his mother* & two FB friends, and is astounded to survey 70+ friends and learn they all genuinely see things in their minds. He also doesn't seem to hear music in his head or dream much, and thinks he gets less out of literature because of the lack of visualizing.

Apparently geneticist Craig Venter is aphantasiac. Also check out Penn (of Penn and Teller) discussing his experience on his podcast (75:15) last year. His experience matches mine perfectly.

* has anyone looked into heritability of this or relatives' scores on tests of mental imagery? maybe aphantasia is the extreme of a normal distribution