Just to follow up on my thread before... I found this on a google search:
"Inability to visualize. Based on brain research, about eight percent of students cannot visualize during reading. This number goes across gender lines, as both boys and girls are affected. Realize that this is not a learning disability; it is how the brain is wired, just like how some people have an affinity for math or literature. Thus, if a child is reading a novel, no matter how descriptive the passages are, that child cannot put images into, or form pictures inside, his or her head."