I wonder if you can improve your visualization ability.

I stopped reading novels for fun about 5-6 years ago but this past year I've started reading at least one book every couple of weeks, and I feel that my ability to visualize things has improved.

On a related note, I wonder how you could measure one's change in visualization ability, since it's so subjective. I had a very difficult time answering the questions in the article, since I had no frame of reference.