Importance of visual imagery during reading

We just started reading my son The Lion, The Witch, and the Wardrobe.  I want to make sure that it is not too advanced for him, that he is starting to visualize the story in his head.

He asked if he could see the movie.  I said no, as I want him to have his own picture first.

Visual imagery during reading is extremely important.  Why?  I have seen students in third grade score high on standardized tests yet they hate reading, and do not enjoy doing it for fun.  The reason I've seen for not liking reading is not visualizing the story in your head.  

Good readers construct mental images as they read a text.  By using prior knowledge and background experiences, readers connect the authors' writing with a personal picture.  Through guided visualization, students learn how to create mental pictures as they read.

Resources:

See http://www.readingrockets.org/strategies/visual_Imagery to watch a teacher model visualization.

www.reading rockets.org